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Date: Mon, 3 Apr 2023 16:01:29 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Nikunj A Dadhania <nikunj@....com>, linux-kernel@...r.kernel.org,
x86@...nel.org
Cc: bp@...en8.de, dionnaglaze@...gle.com, pgonda@...gle.com,
seanjc@...gle.com, pbonzini@...hat.com, michael.roth@....com,
ketanch@...k.ac.in
Subject: Re: [PATCH v2 05/11] x86/sev: Move and reorganize sev guest request
api
On 3/26/23 09:46, Nikunj A Dadhania wrote:
> For enabling Secure TSC, SEV-SNP guests need to communicate with the
> security coprocessor really early during boot. Lot of the required
s/security coprocessor really/AMD Secure Processor/
s/Lot/Many/
> functions are implemented in the sev-guest driver. Move the required
... in the sev-guest driver and therefore not available at early boot.
> functions and provide API to the driver to assign VM communications
s/provide API/provide an API/
s/to assign.*//
> key and send guest request.
>
> Signed-off-by: Nikunj A Dadhania <nikunj@....com>
> ---
> arch/x86/Kconfig | 1 +
> .../x86/include/asm}/sev-guest.h | 6 +
> arch/x86/include/asm/sev.h | 22 +
> arch/x86/kernel/sev.c | 437 ++++++++++++++++-
> drivers/virt/coco/sev-guest/Kconfig | 1 -
> drivers/virt/coco/sev-guest/sev-guest.c | 455 ++----------------
> 6 files changed, 487 insertions(+), 435 deletions(-)
> rename {drivers/virt/coco/sev-guest => arch/x86/include/asm}/sev-guest.h (86%)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index a825bf031f49..42c52bfd2bac 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1545,6 +1545,7 @@ config AMD_MEM_ENCRYPT
> select INSTRUCTION_DECODER
> select ARCH_HAS_CC_PLATFORM
> select X86_MEM_ENCRYPT
> + select CRYPTO_LIB_AESGCM
> help
> Say yes to enable support for the encryption of system memory.
> This requires an AMD processor that supports Secure Memory
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.h b/arch/x86/include/asm/sev-guest.h
> similarity index 86%
> rename from drivers/virt/coco/sev-guest/sev-guest.h
> rename to arch/x86/include/asm/sev-guest.h
> index d245578d988e..834cdae302ad 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.h
> +++ b/arch/x86/include/asm/sev-guest.h
> @@ -12,6 +12,9 @@
>
> #include <linux/types.h>
>
> +#define SNP_REQ_MAX_RETRY_DURATION (60*HZ)
> +#define SNP_REQ_RETRY_DELAY (2*HZ)
> +
> #define MAX_AUTHTAG_LEN 32
> #define AUTHTAG_LEN 16
> #define AAD_LEN 48
> @@ -72,6 +75,9 @@ struct snp_guest_req {
> u8 msg_type;
> };
>
> +int snp_send_guest_request(struct snp_guest_dev *dev, struct snp_guest_req *req);
> +bool snp_assign_vmpck(struct snp_guest_dev *dev, int vmpck_id);
> +
> static inline bool is_vmpck_empty(u8 *vmpck)
> {
> char zero_key[VMPCK_KEY_LEN] = {0};
> diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h
> index ebc271bb6d8e..36868e21c3e0 100644
> --- a/arch/x86/include/asm/sev.h
> +++ b/arch/x86/include/asm/sev.h
> @@ -9,6 +9,7 @@
> #define __ASM_ENCRYPTED_STATE_H
>
> #include <linux/types.h>
> +#include <linux/miscdevice.h>
> #include <asm/insn.h>
> #include <asm/sev-common.h>
> #include <asm/bootparam.h>
> @@ -96,6 +97,27 @@ struct snp_req_data {
>
> struct sev_guest_platform_data {
> u64 secrets_gpa;
> +
> + void *certs_data;
> + struct aesgcm_ctx *ctx;
> + struct snp_guest_msg *req, *resp;
> + struct snp_secrets_page_layout *layout;
> + struct snp_req_data input;
> + u8 *vmpck0;
Isn't this unneeded? You have the vmpck and vmpck_id in the snp_guest_dev
struct which will be set based on the module parameter, so vmpck0 and
associated checks shouldn't be needed.
> +};
> +
> +struct snp_guest_dev {
> + struct device *dev;
> + struct miscdevice misc;
> +
> + /* Mutex to serialize the shared buffer access and command handling. */
> + struct mutex cmd_mutex;
> +
> + struct sev_guest_platform_data *pdata;
> +
> + u32 *os_area_msg_seqno;
> + u8 *vmpck;
> + u8 vmpck_id;
> };
>
> /*
> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> index 3f664ab277c4..c5ca97aab8c1 100644
> --- a/arch/x86/kernel/sev.c
> +++ b/arch/x86/kernel/sev.c
> @@ -22,10 +22,13 @@
> #include <linux/efi.h>
> #include <linux/platform_device.h>
> #include <linux/io.h>
> +#include <linux/psp-sev.h>
> +#include <crypto/gcm.h>
>
> #include <asm/cpu_entry_area.h>
> #include <asm/stacktrace.h>
> #include <asm/sev.h>
> +#include <asm/sev-guest.h>
> #include <asm/insn-eval.h>
> #include <asm/fpu/xcr.h>
> #include <asm/processor.h>
> @@ -982,6 +985,427 @@ static void snp_cleanup_vmsa(struct sev_es_save_area *vmsa)
> free_page((unsigned long)vmsa);
> }
>
> +static struct sev_guest_platform_data *platform_data;
> +
> +/*
> + * If an error is received from the host or AMD Secure Processor (ASP) there
> + * are two options. Either retry the exact same encrypted request or discontinue
> + * using the VMPCK.
> + *
> + * This is because in the current encryption scheme GHCB v2 uses AES-GCM to
> + * encrypt the requests. The IV for this scheme is the sequence number. GCM
> + * cannot tolerate IV reuse.
> + *
> + * The ASP FW v1.51 only increments the sequence numbers on a successful
> + * guest<->ASP back and forth and only accepts messages at its exact sequence
> + * number.
> + *
> + * So if the sequence number were to be reused the encryption scheme is
> + * vulnerable. If the sequence number were incremented for a fresh IV the ASP
> + * will reject the request.
> + */
> +static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
> +{
> + pr_alert("Disabling vmpck_id %d to prevent IV reuse.\n", snp_dev->vmpck_id);
> + memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
> + snp_dev->vmpck = NULL;
> +}
> +
> +static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
> +{
> + u64 count;
> +
> + lockdep_assert_held(&snp_dev->cmd_mutex);
> +
> + /* Read the current message sequence counter from secrets pages */
> + count = *snp_dev->os_area_msg_seqno;
> +
> + return count + 1;
> +}
> +
> +/* Return a non-zero on success */
> +static u64 snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
> +{
> + u64 count = __snp_get_msg_seqno(snp_dev);
> +
> + /*
> + * The message sequence counter for the SNP guest request is a 64-bit
> + * value but the version 2 of GHCB specification defines a 32-bit storage
> + * for it. If the counter exceeds the 32-bit value then return zero.
> + * The caller should check the return value, but if the caller happens to
> + * not check the value and use it, then the firmware treats zero as an
> + * invalid number and will fail the message request.
> + */
> + if (count >= UINT_MAX) {
> + pr_err("SNP request message sequence counter overflow\n");
> + return 0;
> + }
> +
> + return count;
> +}
> +
> +static void snp_inc_msg_seqno(struct snp_guest_dev *snp_dev)
> +{
> + /*
> + * The counter is also incremented by the PSP, so increment it by 2
> + * and save in secrets page.
> + */
> + *snp_dev->os_area_msg_seqno += 2;
> +}
> +
> +static struct aesgcm_ctx *snp_init_crypto(u8 *key, size_t keylen)
> +{
> + struct aesgcm_ctx *ctx;
> +
> + ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
> + if (!ctx)
> + return NULL;
> +
> + if (aesgcm_expandkey(ctx, key, keylen, AUTHTAG_LEN)) {
> + pr_err("SNP: crypto init failed\n");
> + kfree(ctx);
> + return NULL;
> + }
> +
> + return ctx;
> +}
> +
> +static void free_shared_pages(void *buf, size_t sz)
> +{
> + unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
> + int ret;
> +
> + if (!buf)
> + return;
> +
> + ret = set_memory_encrypted((unsigned long)buf, npages);
> + if (ret) {
> + WARN_ONCE(ret, "failed to restore encryption mask (leak it)\n");
> + return;
> + }
> +
> + __free_pages(virt_to_page(buf), get_order(sz));
> +}
> +
> +static void *alloc_shared_pages(size_t sz)
> +{
> + unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
> + struct page *page;
> + int ret;
> +
> + page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(sz));
> + if (!page)
> + return NULL;
> +
> + ret = set_memory_decrypted((unsigned long)page_address(page), npages);
> + if (ret) {
> + pr_err("%s: failed to mark page shared, ret=%d\n", __func__, ret);
> + __free_pages(page, get_order(sz));
> + return NULL;
> + }
> +
> + return page_address(page);
> +}
> +
> +static int snp_setup_psp_messaging(struct sev_guest_platform_data *pdata)
> +{
> + u64 gpa;
> + int ret;
> +
> + if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
> + return -ENODEV;
> +
> + gpa = get_secrets_page();
> + if (!gpa)
> + return -ENODEV;
> +
> + pdata->layout = (__force void *)ioremap_encrypted(gpa, PAGE_SIZE);
> + if (!pdata->layout) {
> + pr_err("Unable to locate AP jump table address: failed to map the SNP secrets page.\n");
> + return -ENODEV;
> + }
> +
> + ret = -EINVAL;
> + pdata->vmpck0 = pdata->layout->vmpck0;
> +
> + /* Verify that VMPCK is not zero. */
> + if (is_vmpck_empty(pdata->vmpck0)) {
> + pr_err("vmpck id 0 is null\n");
> + goto e_unmap;
> + }
> +
> + ret = -ENOMEM;
> + /* Allocate the shared page used for the request and response message. */
> + pdata->req = alloc_shared_pages(sizeof(struct snp_guest_msg));
> + if (!pdata->req)
> + goto e_unmap;
> +
> + pdata->resp = alloc_shared_pages(sizeof(struct snp_guest_msg));
> + if (!pdata->resp)
> + goto e_free_request;
> +
> + pdata->certs_data = alloc_shared_pages(SEV_FW_BLOB_MAX_SIZE);
> + if (!pdata->certs_data)
> + goto e_free_response;
> +
> + ret = -EIO;
> + pdata->ctx = snp_init_crypto(pdata->vmpck0, VMPCK_KEY_LEN);
> + if (!pdata->ctx)
> + goto e_free_cert_data;
> +
> + /* initial the input address for guest request */
> + pdata->input.req_gpa = __pa(pdata->req);
> + pdata->input.resp_gpa = __pa(pdata->resp);
> + pdata->input.data_gpa = __pa(pdata->certs_data);
> +
> + return 0;
> +
> +e_free_cert_data:
> + free_shared_pages(pdata->certs_data, SEV_FW_BLOB_MAX_SIZE);
> +e_free_response:
> + free_shared_pages(pdata->resp, sizeof(struct snp_guest_msg));
> +e_free_request:
> + free_shared_pages(pdata->req, sizeof(struct snp_guest_msg));
> +e_unmap:
> + iounmap(pdata->layout);
> +
> + return ret;
> +}
> +
> +static int __enc_payload(struct aesgcm_ctx *ctx, struct snp_guest_msg *msg,
> + void *plaintext, size_t len)
> +{
> + struct snp_guest_msg_hdr *hdr = &msg->hdr;
> + u8 iv[GCM_AES_IV_SIZE] = {};
> +
> + if (WARN_ON((hdr->msg_sz + ctx->authsize) > sizeof(msg->payload)))
> + return -EBADMSG;
> +
> + memcpy(iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
> + aesgcm_encrypt(ctx, msg->payload, plaintext, len, &hdr->algo, AAD_LEN,
> + iv, hdr->authtag);
> + return 0;
> +}
> +
> +static int dec_payload(struct aesgcm_ctx *ctx, struct snp_guest_msg *msg,
> + void *plaintext, size_t len)
> +{
> + struct snp_guest_msg_hdr *hdr = &msg->hdr;
> + u8 iv[GCM_AES_IV_SIZE] = {};
> +
> + memcpy(iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
> + if (aesgcm_decrypt(ctx, plaintext, msg->payload, len, &hdr->algo,
> + AAD_LEN, iv, hdr->authtag))
> + return 0;
> + else
> + return -EBADMSG;
> +}
> +
> +static int verify_and_dec_payload(struct sev_guest_platform_data *pdata,
> + void *payload, u32 sz)
> +{
> + struct snp_guest_msg *resp = pdata->resp;
> + struct snp_guest_msg *req = pdata->req;
> + struct snp_guest_msg_hdr *req_hdr = &req->hdr;
> + struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
> + struct aesgcm_ctx *ctx = pdata->ctx;
> +
> + pr_debug("response [seqno %lld type %d version %d sz %d]\n",
> + resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version,
> + resp_hdr->msg_sz);
> +
> + /* Verify that the sequence counter is incremented by 1 */
> + if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
> + return -EBADMSG;
> +
> + /* Verify response message type and version number. */
> + if (resp_hdr->msg_type != (req_hdr->msg_type + 1) ||
> + resp_hdr->msg_version != req_hdr->msg_version)
> + return -EBADMSG;
> +
> + /*
> + * If the message size is greater than our buffer length then return
> + * an error.
> + */
> + if (unlikely((resp_hdr->msg_sz + ctx->authsize) > sz))
> + return -EBADMSG;
> +
> + return dec_payload(ctx, resp, payload, resp_hdr->msg_sz);
> +}
> +
> +static int enc_payload(struct sev_guest_platform_data *pdata, u64 seqno,
> + struct snp_guest_req *req, u8 vmpck_id)
> +{
> + struct snp_guest_msg *msg = pdata->req;
> + struct snp_guest_msg_hdr *hdr = &msg->hdr;
> +
> + memset(msg, 0, sizeof(*msg));
> +
> + hdr->algo = SNP_AEAD_AES_256_GCM;
> + hdr->hdr_version = MSG_HDR_VER;
> + hdr->hdr_sz = sizeof(*hdr);
> + hdr->msg_type = req->msg_type;
> + hdr->msg_version = req->msg_version;
> + hdr->msg_seqno = seqno;
> + hdr->msg_vmpck = vmpck_id;
> + hdr->msg_sz = req->req_sz;
> +
> + /* Verify the sequence number is non-zero */
> + if (!hdr->msg_seqno)
> + return -ENOSR;
> +
> + pr_debug("request [seqno %lld type %d version %d sz %d]\n",
> + hdr->msg_seqno, hdr->msg_type, hdr->msg_version, hdr->msg_sz);
> +
> + return __enc_payload(pdata->ctx, msg, req->req_buf, req->req_sz);
> +}
> +
> +static int __handle_guest_request(struct snp_guest_dev *snp_dev,
> + struct sev_guest_platform_data *pdata,
> + struct snp_guest_req *req)
> +{
> + unsigned long err = 0xff, override_err = 0;
> + unsigned long req_start = jiffies;
> + unsigned int override_npages = 0;
> + int rc;
> +
> +retry_request:
> + /*
> + * Call firmware to process the request. In this function the encrypted
> + * message enters shared memory with the host. So after this call the
> + * sequence number must be incremented or the VMPCK must be deleted to
> + * prevent reuse of the IV.
> + */
> + rc = snp_issue_guest_request(req->exit_code, &pdata->input, &err);
> + switch (rc) {
> + case -ENOSPC:
> + /*
> + * If the extended guest request fails due to having too
> + * small of a certificate data buffer, retry the same
> + * guest request without the extended data request in
> + * order to increment the sequence number and thus avoid
> + * IV reuse.
> + */
> + override_npages = pdata->input.data_npages;
> + req->exit_code = SVM_VMGEXIT_GUEST_REQUEST;
> +
> + /*
> + * Override the error to inform callers the given extended
> + * request buffer size was too small and give the caller the
> + * required buffer size.
> + */
> + override_err = SNP_GUEST_REQ_INVALID_LEN;
> +
> + /*
> + * If this call to the firmware succeeds, the sequence number can
> + * be incremented allowing for continued use of the VMPCK. If
> + * there is an error reflected in the return value, this value
> + * is checked further down and the result will be the deletion
> + * of the VMPCK and the error code being propagated back to the
> + * user as an ioctl() return code.
> + */
> + goto retry_request;
> +
> + /*
> + * The host may return SNP_GUEST_REQ_ERR_EBUSY if the request has been
> + * throttled. Retry in the driver to avoid returning and reusing the
> + * message sequence number on a different message.
> + */
> + case -EAGAIN:
> + if (jiffies - req_start > SNP_REQ_MAX_RETRY_DURATION) {
> + rc = -ETIMEDOUT;
> + break;
> + }
> + schedule_timeout_killable(SNP_REQ_RETRY_DELAY);
> + goto retry_request;
> + }
> +
> + /*
> + * Increment the message sequence number. There is no harm in doing
> + * this now because decryption uses the value stored in the response
> + * structure and any failure will wipe the VMPCK, preventing further
> + * use anyway.
> + */
> + snp_inc_msg_seqno(snp_dev);
> +
> + if (req->fw_err)
> + *req->fw_err = override_err ?: err;
> +
> + if (override_npages)
> + pdata->input.data_npages = override_npages;
> +
> + /*
> + * If an extended guest request was issued and the supplied certificate
> + * buffer was not large enough, a standard guest request was issued to
> + * prevent IV reuse. If the standard request was successful, return -EIO
> + * back to the caller as would have originally been returned.
> + */
> + if (!rc && override_err == SNP_GUEST_REQ_INVALID_LEN)
> + return -EIO;
> +
> + return rc;
> +}
> +
> +int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req)
> +{
> + struct sev_guest_platform_data *pdata;
> + u64 seqno;
> + int rc;
> +
> + if (!snp_dev || !snp_dev->pdata || !req)
> + return -ENODEV;
> +
> + pdata = snp_dev->pdata;
> +
> + /* Get message sequence and verify that its a non-zero */
> + seqno = snp_get_msg_seqno(snp_dev);
> + if (!seqno)
> + return -EIO;
> +
> + memset(pdata->resp, 0, sizeof(struct snp_guest_msg));
> +
> + /* Encrypt the provided payload */
> + rc = enc_payload(pdata, seqno, req, snp_dev->vmpck_id);
> + if (rc)
> + return rc;
> +
> + rc = __handle_guest_request(snp_dev, pdata, req);
> + if (rc) {
> + if (rc == -EIO && *req->fw_err == SNP_GUEST_REQ_INVALID_LEN)
> + return rc;
> +
> + pr_alert("Detected error from ASP request. rc: %d, fw_err: %llu\n",
> + rc, *req->fw_err);
> + snp_disable_vmpck(snp_dev);
> + return rc;
> + }
> +
> + rc = verify_and_dec_payload(pdata, req->resp_buf, req->resp_sz);
> + if (rc) {
> + pr_alert("Detected unexpected decode failure from ASP. rc: %d\n", rc);
> + snp_disable_vmpck(snp_dev);
> + return rc;
> + }
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(snp_send_guest_request);
> +
> +bool snp_assign_vmpck(struct snp_guest_dev *dev, int vmpck_id)
> +{
> + struct sev_guest_platform_data *pdata = dev->pdata;
> +
> + if (!pdata || WARN_ON(vmpck_id > 3))
> + return false;
> +
> + dev->vmpck_id = vmpck_id;
> + dev->vmpck = pdata->layout->vmpck0 + vmpck_id * VMPCK_KEY_LEN;
> + dev->os_area_msg_seqno = &pdata->layout->os_area.msg_seqno_0 + vmpck_id;
> +
> + return true;
> +}
> +EXPORT_SYMBOL_GPL(snp_assign_vmpck);
> +
> static int wakeup_cpu_via_vmgexit(int apic_id, unsigned long start_ip)
> {
> struct sev_es_save_area *cur_vmsa, *vmsa;
> @@ -2247,18 +2671,17 @@ static struct platform_device sev_guest_device = {
>
> static int __init snp_init_platform_device(void)
> {
> - struct sev_guest_platform_data data;
> - u64 gpa;
> -
> if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
> return -ENODEV;
>
> - gpa = get_secrets_page();
> - if (!gpa)
> + platform_data = kzalloc(sizeof(*platform_data), GFP_KERNEL);
> + if (!platform_data)
> + return -ENOMEM;
> +
> + if (snp_setup_psp_messaging(platform_data))
This shouldn't be done here (or yet) since you only moving the routines.
The sev-guest driver should call this regardless of the vmpck_id value.
> return -ENODEV;
>
> - data.secrets_gpa = gpa;
> - if (platform_device_add_data(&sev_guest_device, &data, sizeof(data)))
> + if (platform_device_add_data(&sev_guest_device, platform_data, sizeof(*platform_data)))
> return -ENODEV;
>
> if (platform_device_register(&sev_guest_device))
> diff --git a/drivers/virt/coco/sev-guest/Kconfig b/drivers/virt/coco/sev-guest/Kconfig
> index bcc760bfb468..c130456ad401 100644
> --- a/drivers/virt/coco/sev-guest/Kconfig
> +++ b/drivers/virt/coco/sev-guest/Kconfig
> @@ -2,7 +2,6 @@ config SEV_GUEST
> tristate "AMD SEV Guest driver"
> default m
> depends on AMD_MEM_ENCRYPT
> - select CRYPTO_LIB_AESGCM
> help
> SEV-SNP firmware provides the guest a mechanism to communicate with
> the PSP without risk from a malicious hypervisor who wishes to read,
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index 4901ebc8fa1a..a011df21c03a 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> @@ -24,110 +24,25 @@
> #include <asm/svm.h>
> #include <asm/sev.h>
>
> -#include "sev-guest.h"
> +#include <asm/sev-guest.h>
>
> #define DEVICE_NAME "sev-guest"
>
> -#define SNP_REQ_MAX_RETRY_DURATION (60*HZ)
> -#define SNP_REQ_RETRY_DELAY (2*HZ)
> -
> -struct snp_guest_dev {
> - struct device *dev;
> - struct miscdevice misc;
> -
> - /* Mutex to serialize the shared buffer access and command handling. */
> - struct mutex cmd_mutex;
> -
> - void *certs_data;
> - struct aesgcm_ctx *ctx;
> - struct snp_guest_msg *request, *response;
> - struct snp_secrets_page_layout *layout;
> - struct snp_req_data input;
> - u32 *os_area_msg_seqno;
> - u8 *vmpck;
> - u8 vmpck_id;
> -};
> -
> static u32 vmpck_id;
> module_param(vmpck_id, uint, 0444);
> MODULE_PARM_DESC(vmpck_id, "The VMPCK ID to use when communicating with the PSP.");
>
> static inline unsigned int get_ctx_authsize(struct snp_guest_dev *snp_dev)
> {
> - if (snp_dev && snp_dev->ctx)
> - return snp_dev->ctx->authsize;
> + struct sev_guest_platform_data *pdata = snp_dev->pdata;
> +
> + if (pdata && pdata->ctx)
> + return pdata->ctx->authsize;
>
> WARN_ONCE(1, "Unable to get crypto authsize\n");
> return 0;
> }
>
> -/*
> - * If an error is received from the host or AMD Secure Processor (ASP) there
> - * are two options. Either retry the exact same encrypted request or discontinue
> - * using the VMPCK.
> - *
> - * This is because in the current encryption scheme GHCB v2 uses AES-GCM to
> - * encrypt the requests. The IV for this scheme is the sequence number. GCM
> - * cannot tolerate IV reuse.
> - *
> - * The ASP FW v1.51 only increments the sequence numbers on a successful
> - * guest<->ASP back and forth and only accepts messages at its exact sequence
> - * number.
> - *
> - * So if the sequence number were to be reused the encryption scheme is
> - * vulnerable. If the sequence number were incremented for a fresh IV the ASP
> - * will reject the request.
> - */
> -static void snp_disable_vmpck(struct snp_guest_dev *snp_dev)
> -{
> - dev_alert(snp_dev->dev, "Disabling vmpck_id %d to prevent IV reuse.\n",
> - snp_dev->vmpck_id);
> - memzero_explicit(snp_dev->vmpck, VMPCK_KEY_LEN);
> - snp_dev->vmpck = NULL;
> -}
> -
> -static inline u64 __snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
> -{
> - u64 count;
> -
> - lockdep_assert_held(&snp_dev->cmd_mutex);
> -
> - /* Read the current message sequence counter from secrets pages */
> - count = *snp_dev->os_area_msg_seqno;
> -
> - return count + 1;
> -}
> -
> -/* Return a non-zero on success */
> -static u64 snp_get_msg_seqno(struct snp_guest_dev *snp_dev)
> -{
> - u64 count = __snp_get_msg_seqno(snp_dev);
> -
> - /*
> - * The message sequence counter for the SNP guest request is a 64-bit
> - * value but the version 2 of GHCB specification defines a 32-bit storage
> - * for it. If the counter exceeds the 32-bit value then return zero.
> - * The caller should check the return value, but if the caller happens to
> - * not check the value and use it, then the firmware treats zero as an
> - * invalid number and will fail the message request.
> - */
> - if (count >= UINT_MAX) {
> - dev_err(snp_dev->dev, "request message sequence counter overflow\n");
> - return 0;
> - }
> -
> - return count;
> -}
> -
> -static void snp_inc_msg_seqno(struct snp_guest_dev *snp_dev)
> -{
> - /*
> - * The counter is also incremented by the PSP, so increment it by 2
> - * and save in secrets page.
> - */
> - *snp_dev->os_area_msg_seqno += 2;
> -}
> -
> static inline struct snp_guest_dev *to_snp_dev(struct file *file)
> {
> struct miscdevice *dev = file->private_data;
> @@ -135,236 +50,6 @@ static inline struct snp_guest_dev *to_snp_dev(struct file *file)
> return container_of(dev, struct snp_guest_dev, misc);
> }
>
> -static struct aesgcm_ctx *snp_init_crypto(u8 *key, size_t keylen)
> -{
> - struct aesgcm_ctx *ctx;
> -
> - ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
> - if (!ctx)
> - return NULL;
> -
> - if (aesgcm_expandkey(ctx, key, keylen, AUTHTAG_LEN)) {
> - pr_err("SNP: crypto init failed\n");
> - kfree(ctx);
> - return NULL;
> - }
> -
> - return ctx;
> -}
> -
> -static int __enc_payload(struct aesgcm_ctx *ctx, struct snp_guest_msg *msg,
> - void *plaintext, size_t len)
> -{
> - struct snp_guest_msg_hdr *hdr = &msg->hdr;
> - u8 iv[GCM_AES_IV_SIZE] = {};
> -
> - if (WARN_ON((hdr->msg_sz + ctx->authsize) > sizeof(msg->payload)))
> - return -EBADMSG;
> -
> - memcpy(iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
> - aesgcm_encrypt(ctx, msg->payload, plaintext, len, &hdr->algo, AAD_LEN,
> - iv, hdr->authtag);
> - return 0;
> -}
> -
> -static int dec_payload(struct aesgcm_ctx *ctx, struct snp_guest_msg *msg,
> - void *plaintext, size_t len)
> -{
> - struct snp_guest_msg_hdr *hdr = &msg->hdr;
> - u8 iv[GCM_AES_IV_SIZE] = {};
> -
> - memcpy(iv, &hdr->msg_seqno, sizeof(hdr->msg_seqno));
> - if (aesgcm_decrypt(ctx, plaintext, msg->payload, len, &hdr->algo,
> - AAD_LEN, iv, hdr->authtag))
> - return 0;
> - else
> - return -EBADMSG;
> -}
> -
> -static int verify_and_dec_payload(struct snp_guest_dev *snp_dev, void *payload, u32 sz)
> -{
> - struct snp_guest_msg *resp = snp_dev->response;
> - struct snp_guest_msg *req = snp_dev->request;
> - struct snp_guest_msg_hdr *req_hdr = &req->hdr;
> - struct snp_guest_msg_hdr *resp_hdr = &resp->hdr;
> - struct aesgcm_ctx *ctx = snp_dev->ctx;
> -
> - pr_debug("response [seqno %lld type %d version %d sz %d]\n",
> - resp_hdr->msg_seqno, resp_hdr->msg_type, resp_hdr->msg_version,
> - resp_hdr->msg_sz);
> -
> - /* Verify that the sequence counter is incremented by 1 */
> - if (unlikely(resp_hdr->msg_seqno != (req_hdr->msg_seqno + 1)))
> - return -EBADMSG;
> -
> - /* Verify response message type and version number. */
> - if (resp_hdr->msg_type != (req_hdr->msg_type + 1) ||
> - resp_hdr->msg_version != req_hdr->msg_version)
> - return -EBADMSG;
> -
> - /*
> - * If the message size is greater than our buffer length then return
> - * an error.
> - */
> - if (unlikely((resp_hdr->msg_sz + ctx->authsize) > sz))
> - return -EBADMSG;
> -
> - /* Decrypt the payload */
> - return dec_payload(ctx, resp, payload, resp_hdr->msg_sz);
> -}
> -
> -static int enc_payload(struct snp_guest_dev *snp_dev, u64 seqno,
> - struct snp_guest_req *req, u8 __vmpck_id)
> -{
> - struct snp_guest_msg *msg = snp_dev->request;
> - struct snp_guest_msg_hdr *hdr = &msg->hdr;
> -
> - memset(msg, 0, sizeof(*msg));
> -
> - hdr->algo = SNP_AEAD_AES_256_GCM;
> - hdr->hdr_version = MSG_HDR_VER;
> - hdr->hdr_sz = sizeof(*hdr);
> - hdr->msg_type = req->msg_type;
> - hdr->msg_version = req->msg_version;
> - hdr->msg_seqno = seqno;
> - hdr->msg_vmpck = __vmpck_id;
> - hdr->msg_sz = req->req_sz;
> -
> - /* Verify the sequence number is non-zero */
> - if (!hdr->msg_seqno)
> - return -ENOSR;
> -
> - pr_debug("request [seqno %lld type %d version %d sz %d]\n",
> - hdr->msg_seqno, hdr->msg_type, hdr->msg_version, hdr->msg_sz);
> -
> - return __enc_payload(snp_dev->ctx, msg, req->req_buf, req->req_sz);
> -}
> -
> -static int __handle_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req)
> -{
> - unsigned long err = 0xff, override_err = 0;
> - unsigned long req_start = jiffies;
> - unsigned int override_npages = 0;
> - int rc;
> -
> -retry_request:
> - /*
> - * Call firmware to process the request. In this function the encrypted
> - * message enters shared memory with the host. So after this call the
> - * sequence number must be incremented or the VMPCK must be deleted to
> - * prevent reuse of the IV.
> - */
> - rc = snp_issue_guest_request(req->exit_code, &snp_dev->input, &err);
> - switch (rc) {
> - case -ENOSPC:
> - /*
> - * If the extended guest request fails due to having too
> - * small of a certificate data buffer, retry the same
> - * guest request without the extended data request in
> - * order to increment the sequence number and thus avoid
> - * IV reuse.
> - */
> - override_npages = snp_dev->input.data_npages;
> - req->exit_code = SVM_VMGEXIT_GUEST_REQUEST;
> -
> - /*
> - * Override the error to inform callers the given extended
> - * request buffer size was too small and give the caller the
> - * required buffer size.
> - */
> - override_err = SNP_GUEST_REQ_INVALID_LEN;
> -
> - /*
> - * If this call to the firmware succeeds, the sequence number can
> - * be incremented allowing for continued use of the VMPCK. If
> - * there is an error reflected in the return value, this value
> - * is checked further down and the result will be the deletion
> - * of the VMPCK and the error code being propagated back to the
> - * user as an ioctl() return code.
> - */
> - goto retry_request;
> -
> - /*
> - * The host may return SNP_GUEST_REQ_ERR_EBUSY if the request has been
> - * throttled. Retry in the driver to avoid returning and reusing the
> - * message sequence number on a different message.
> - */
> - case -EAGAIN:
> - if (jiffies - req_start > SNP_REQ_MAX_RETRY_DURATION) {
> - rc = -ETIMEDOUT;
> - break;
> - }
> - schedule_timeout_killable(SNP_REQ_RETRY_DELAY);
> - goto retry_request;
> - }
> -
> - /*
> - * Increment the message sequence number. There is no harm in doing
> - * this now because decryption uses the value stored in the response
> - * structure and any failure will wipe the VMPCK, preventing further
> - * use anyway.
> - */
> - snp_inc_msg_seqno(snp_dev);
> -
> - if (req->fw_err)
> - *req->fw_err = override_err ?: err;
> -
> - if (override_npages)
> - snp_dev->input.data_npages = override_npages;
> -
> - /*
> - * If an extended guest request was issued and the supplied certificate
> - * buffer was not large enough, a standard guest request was issued to
> - * prevent IV reuse. If the standard request was successful, return -EIO
> - * back to the caller as would have originally been returned.
> - */
> - if (!rc && override_err == SNP_GUEST_REQ_INVALID_LEN)
> - return -EIO;
> -
> - return rc;
> -}
> -
> -static int snp_send_guest_request(struct snp_guest_dev *snp_dev, struct snp_guest_req *req)
> -{
> - u64 seqno;
> - int rc;
> -
> - if (!snp_dev || !req)
> - return -ENODEV;
> -
> - /* Get message sequence and verify that its a non-zero */
> - seqno = snp_get_msg_seqno(snp_dev);
> - if (!seqno)
> - return -EIO;
> -
> - memset(snp_dev->response, 0, sizeof(struct snp_guest_msg));
> -
> - /* Encrypt the userspace provided payload */
> - rc = enc_payload(snp_dev, seqno, req, snp_dev->vmpck_id);
> - if (rc)
> - return rc;
> -
> - rc = __handle_guest_request(snp_dev, req);
> - if (rc) {
> - if (rc == -EIO && *req->fw_err == SNP_GUEST_REQ_INVALID_LEN)
> - return rc;
> -
> - dev_alert(snp_dev->dev, "Detected error from ASP request. rc: %d, fw_err: %llu\n",
> - rc, *req->fw_err);
> - snp_disable_vmpck(snp_dev);
> - return rc;
> - }
> -
> - rc = verify_and_dec_payload(snp_dev, req->resp_buf, req->resp_sz);
> - if (rc) {
> - dev_alert(snp_dev->dev, "Detected unexpected decode failure from ASP. rc: %d\n", rc);
> - snp_disable_vmpck(snp_dev);
> - return rc;
> - }
> -
> - return 0;
> -}
> -
> static int handle_guest_request(struct snp_guest_dev *snp_dev, u64 exit_code, u8 msg_version,
> u8 msg_type, void *req_buf, size_t req_sz, void *resp_buf,
> u32 resp_sz, __u64 *fw_err)
> @@ -463,12 +148,14 @@ static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_reque
>
> static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg)
> {
> + struct sev_guest_platform_data *pdata;
> struct snp_ext_report_req req;
> struct snp_report_resp *resp;
> int ret, npages = 0, resp_len;
>
> lockdep_assert_held(&snp_dev->cmd_mutex);
>
> + pdata = snp_dev->pdata;
> if (!arg->req_data || !arg->resp_data)
> return -EINVAL;
>
> @@ -492,7 +179,7 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
> * the host. If host does not supply any certs in it, then copy
> * zeros to indicate that certificate data was not provided.
> */
> - memset(snp_dev->certs_data, 0, req.certs_len);
> + memset(pdata->certs_data, 0, req.certs_len);
> npages = req.certs_len >> PAGE_SHIFT;
> cmd:
> /*
> @@ -505,14 +192,14 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
> if (!resp)
> return -ENOMEM;
>
> - snp_dev->input.data_npages = npages;
> + pdata->input.data_npages = npages;
> ret = handle_guest_request(snp_dev, SVM_VMGEXIT_EXT_GUEST_REQUEST, arg->msg_version,
> SNP_MSG_REPORT_REQ, &req.data,
> sizeof(req.data), resp->data, resp_len, &arg->fw_err);
>
> /* If certs length is invalid then copy the returned length */
> if (arg->fw_err == SNP_GUEST_REQ_INVALID_LEN) {
> - req.certs_len = snp_dev->input.data_npages << PAGE_SHIFT;
> + req.certs_len = pdata->input.data_npages << PAGE_SHIFT;
>
> if (copy_to_user((void __user *)arg->req_data, &req, sizeof(req)))
> ret = -EFAULT;
> @@ -522,7 +209,7 @@ static int get_ext_report(struct snp_guest_dev *snp_dev, struct snp_guest_reques
> goto e_free;
>
> if (npages &&
> - copy_to_user((void __user *)req.certs_address, snp_dev->certs_data,
> + copy_to_user((void __user *)req.certs_address, pdata->certs_data,
> req.certs_len)) {
> ret = -EFAULT;
> goto e_free;
> @@ -583,68 +270,17 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long
> return ret;
> }
>
> -static void free_shared_pages(void *buf, size_t sz)
> -{
> - unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
> - int ret;
> -
> - if (!buf)
> - return;
> -
> - ret = set_memory_encrypted((unsigned long)buf, npages);
> - if (ret) {
> - WARN_ONCE(ret, "failed to restore encryption mask (leak it)\n");
> - return;
> - }
> -
> - __free_pages(virt_to_page(buf), get_order(sz));
> -}
> -
> -static void *alloc_shared_pages(struct device *dev, size_t sz)
> -{
> - unsigned int npages = PAGE_ALIGN(sz) >> PAGE_SHIFT;
> - struct page *page;
> - int ret;
> -
> - page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(sz));
> - if (!page)
> - return NULL;
> -
> - ret = set_memory_decrypted((unsigned long)page_address(page), npages);
> - if (ret) {
> - dev_err(dev, "failed to mark page shared, ret=%d\n", ret);
> - __free_pages(page, get_order(sz));
> - return NULL;
> - }
> -
> - return page_address(page);
> -}
> -
> static const struct file_operations snp_guest_fops = {
> .owner = THIS_MODULE,
> .unlocked_ioctl = snp_guest_ioctl,
> };
>
> -bool snp_assign_vmpck(struct snp_guest_dev *dev, int vmpck_id)
> -{
> - if (WARN_ON(vmpck_id > 3))
> - return false;
> -
> - dev->vmpck_id = vmpck_id;
> - dev->vmpck = dev->layout->vmpck0 + vmpck_id * VMPCK_KEY_LEN;
> - dev->os_area_msg_seqno = &dev->layout->os_area.msg_seqno_0 + vmpck_id;
> -
> - return true;
> -}
> -
> static int __init sev_guest_probe(struct platform_device *pdev)
> {
> - struct snp_secrets_page_layout *layout;
> - struct sev_guest_platform_data *data;
> + struct sev_guest_platform_data *pdata;
> struct device *dev = &pdev->dev;
> struct snp_guest_dev *snp_dev;
> struct miscdevice *misc;
> - void __iomem *mapping;
> int ret;
>
> if (!cc_platform_has(CC_ATTR_GUEST_SEV_SNP))
> @@ -653,80 +289,48 @@ static int __init sev_guest_probe(struct platform_device *pdev)
> if (!dev->platform_data)
> return -ENODEV;
>
> - data = (struct sev_guest_platform_data *)dev->platform_data;
> - mapping = ioremap_encrypted(data->secrets_gpa, PAGE_SIZE);
> - if (!mapping)
> - return -ENODEV;
> -
> - layout = (__force void *)mapping;
> -
> - ret = -ENOMEM;
> + pdata = (struct sev_guest_platform_data *)dev->platform_data;
> snp_dev = devm_kzalloc(&pdev->dev, sizeof(struct snp_guest_dev), GFP_KERNEL);
> if (!snp_dev)
> - goto e_unmap;
> + return -ENOMEM;
>
> ret = -EINVAL;
> - snp_dev->layout = layout;
> + snp_dev->pdata = pdata;
> if (!snp_assign_vmpck(snp_dev, vmpck_id)) {
> dev_err(dev, "invalid vmpck id %d\n", vmpck_id);
> - goto e_unmap;
> + goto e_free_snpdev;
> }
>
> /* Verify that VMPCK is not zero. */
> if (is_vmpck_empty(snp_dev->vmpck)) {
> dev_err(dev, "vmpck id %d is null\n", vmpck_id);
> - goto e_unmap;
> + goto e_free_snpdev;
> + }
> +
> + /* Skip VMPCK0 initialization as the key is already initialized during early boot */
> + if (vmpck_id && aesgcm_expandkey(pdata->ctx, snp_dev->vmpck, VMPCK_KEY_LEN, AUTHTAG_LEN)) {
See previous comment. The sev-guest driver should be setting up everything
private to it no matter the vmpck to be used.
Thanks,
Tom
> + ret = -ENODEV;
> + goto e_free_snpdev;
> }
>
> mutex_init(&snp_dev->cmd_mutex);
> platform_set_drvdata(pdev, snp_dev);
> snp_dev->dev = dev;
>
> - /* Allocate the shared page used for the request and response message. */
> - snp_dev->request = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
> - if (!snp_dev->request)
> - goto e_unmap;
> -
> - snp_dev->response = alloc_shared_pages(dev, sizeof(struct snp_guest_msg));
> - if (!snp_dev->response)
> - goto e_free_request;
> -
> - snp_dev->certs_data = alloc_shared_pages(dev, SEV_FW_BLOB_MAX_SIZE);
> - if (!snp_dev->certs_data)
> - goto e_free_response;
> -
> - ret = -EIO;
> - snp_dev->ctx = snp_init_crypto(snp_dev->vmpck, VMPCK_KEY_LEN);
> - if (!snp_dev->ctx)
> - goto e_free_cert_data;
> -
> misc = &snp_dev->misc;
> misc->minor = MISC_DYNAMIC_MINOR;
> misc->name = DEVICE_NAME;
> misc->fops = &snp_guest_fops;
>
> - /* initial the input address for guest request */
> - snp_dev->input.req_gpa = __pa(snp_dev->request);
> - snp_dev->input.resp_gpa = __pa(snp_dev->response);
> - snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
> -
> - ret = misc_register(misc);
> + ret = misc_register(misc);
> if (ret)
> - goto e_free_ctx;
> + goto e_free_snpdev;
>
> dev_info(dev, "Initialized SEV guest driver (using vmpck_id %d)\n", vmpck_id);
> return 0;
>
> -e_free_ctx:
> - kfree(snp_dev->ctx);
> -e_free_cert_data:
> - free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE);
> -e_free_response:
> - free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
> -e_free_request:
> - free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
> -e_unmap:
> - iounmap(mapping);
> +e_free_snpdev:
> + kfree(snp_dev);
> return ret;
> }
>
> @@ -734,11 +338,8 @@ static int __exit sev_guest_remove(struct platform_device *pdev)
> {
> struct snp_guest_dev *snp_dev = platform_get_drvdata(pdev);
>
> - free_shared_pages(snp_dev->certs_data, SEV_FW_BLOB_MAX_SIZE);
> - free_shared_pages(snp_dev->response, sizeof(struct snp_guest_msg));
> - free_shared_pages(snp_dev->request, sizeof(struct snp_guest_msg));
> - kfree(snp_dev->ctx);
> misc_deregister(&snp_dev->misc);
> + kfree(snp_dev);
>
> return 0;
> }
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