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Date: Fri, 13 Jan 2023 16:34:31 -0600
From: "Kalra, Ashish" <ashish.kalra@....com>
To: Alper Gun <alpergun@...gle.com>,
Michael Roth <michael.roth@....com>
Cc: kvm@...r.kernel.org, linux-coco@...ts.linux.dev,
linux-mm@...ck.org, linux-crypto@...r.kernel.org, x86@...nel.org,
linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
jroedel@...e.de, thomas.lendacky@....com, hpa@...or.com,
ardb@...nel.org, pbonzini@...hat.com, seanjc@...gle.com,
vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
luto@...nel.org, dave.hansen@...ux.intel.com, slp@...hat.com,
pgonda@...gle.com, peterz@...radead.org,
srinivas.pandruvada@...ux.intel.com, rientjes@...gle.com,
dovmurik@...ux.ibm.com, tobin@....com, bp@...en8.de,
vbabka@...e.cz, kirill@...temov.name, ak@...ux.intel.com,
tony.luck@...el.com, marcorr@...gle.com,
sathyanarayanan.kuppuswamy@...ux.intel.com, dgilbert@...hat.com,
jarkko@...nel.org, harald@...fian.com,
Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH RFC v7 29/64] crypto: ccp: Handle the legacy SEV command
when SNP is enabled
Hello Alper,
On 1/12/2023 5:45 PM, Alper Gun wrote:
> On Wed, Dec 14, 2022 at 11:54 AM Michael Roth <michael.roth@....com> wrote:
>>
>> From: Brijesh Singh <brijesh.singh@....com>
>>
>> The behavior of the SEV-legacy commands is altered when the SNP firmware
>> is in the INIT state. When SNP is in INIT state, all the SEV-legacy
>> commands that cause the firmware to write to memory must be in the
>> firmware state before issuing the command..
>>
>> A command buffer may contains a system physical address that the firmware
>> may write to. There are two cases that need to be handled:
>>
>> 1) system physical address points to a guest memory
>> 2) system physical address points to a host memory
>>
>> To handle the case #1, change the page state to the firmware in the RMP
>> table before issuing the command and restore the state to shared after the
>> command completes.
>>
>> For the case #2, use a bounce buffer to complete the request.
>>
>> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
>> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
>> Signed-off-by: Michael Roth <michael.roth@....com>
>> ---
>> drivers/crypto/ccp/sev-dev.c | 370 ++++++++++++++++++++++++++++++++++-
>> drivers/crypto/ccp/sev-dev.h | 12 ++
>> 2 files changed, 372 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
>> index 4c12e98a1219..5eb2e8f364d4 100644
>> --- a/drivers/crypto/ccp/sev-dev.c
>> +++ b/drivers/crypto/ccp/sev-dev.c
>> @@ -286,6 +286,30 @@ static int rmp_mark_pages_firmware(unsigned long paddr, unsigned int npages, boo
>> return rc;
>> }
>>
>> +static int rmp_mark_pages_shared(unsigned long paddr, unsigned int npages)
>> +{
>> + /* Cbit maybe set in the paddr */
>> + unsigned long pfn = __sme_clr(paddr) >> PAGE_SHIFT;
>> + int rc, n = 0, i;
>> +
>> + for (i = 0; i < npages; i++, pfn++, n++) {
>> + rc = rmp_make_shared(pfn, PG_LEVEL_4K);
>> + if (rc)
>> + goto cleanup;
>> + }
>> +
>> + return 0;
>> +
>> +cleanup:
>> + /*
>> + * If failed to change the page state to shared, then its not safe
>> + * to release the page back to the system, leak it.
>> + */
>> + snp_mark_pages_offline(pfn, npages - n);
>> +
>> + return rc;
>> +}
>> +
>> static struct page *__snp_alloc_firmware_pages(gfp_t gfp_mask, int order, bool locked)
>> {
>> unsigned long npages = 1ul << order, paddr;
>> @@ -487,12 +511,295 @@ static int sev_write_init_ex_file_if_required(int cmd_id)
>> return sev_write_init_ex_file();
>> }
>>
>> +static int alloc_snp_host_map(struct sev_device *sev)
>> +{
>> + struct page *page;
>> + int i;
>> +
>> + for (i = 0; i < MAX_SNP_HOST_MAP_BUFS; i++) {
>> + struct snp_host_map *map = &sev->snp_host_map[i];
>> +
>> + memset(map, 0, sizeof(*map));
>> +
>> + page = alloc_pages(GFP_KERNEL_ACCOUNT, get_order(SEV_FW_BLOB_MAX_SIZE));
>> + if (!page)
>> + return -ENOMEM;
>> +
>> + map->host = page_address(page);
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static void free_snp_host_map(struct sev_device *sev)
>> +{
>> + int i;
>> +
>> + for (i = 0; i < MAX_SNP_HOST_MAP_BUFS; i++) {
>> + struct snp_host_map *map = &sev->snp_host_map[i];
>> +
>> + if (map->host) {
>> + __free_pages(virt_to_page(map->host), get_order(SEV_FW_BLOB_MAX_SIZE));
>> + memset(map, 0, sizeof(*map));
>> + }
>> + }
>> +}
>> +
>> +static int map_firmware_writeable(u64 *paddr, u32 len, bool guest, struct snp_host_map *map)
>> +{
>> + unsigned int npages = PAGE_ALIGN(len) >> PAGE_SHIFT;
>> +
>> + map->active = false;
>> +
>> + if (!paddr || !len)
>> + return 0;
>> +
>> + map->paddr = *paddr;
>> + map->len = len;
>> +
>> + /* If paddr points to a guest memory then change the page state to firmwware. */
>> + if (guest) {
>> + if (rmp_mark_pages_firmware(*paddr, npages, true))
>> + return -EFAULT;
>> +
>> + goto done;
>> + }
>> +
>> + if (!map->host)
>> + return -ENOMEM;
>> +
>> + /* Check if the pre-allocated buffer can be used to fullfil the request. */
>> + if (len > SEV_FW_BLOB_MAX_SIZE)
>> + return -EINVAL;
>> +
>> + /* Transition the pre-allocated buffer to the firmware state. */
>> + if (rmp_mark_pages_firmware(__pa(map->host), npages, true))
>> + return -EFAULT;
>> +
>> + /* Set the paddr to use pre-allocated firmware buffer */
>> + *paddr = __psp_pa(map->host);
>> +
>> +done:
>> + map->active = true;
>> + return 0;
>> +}
>> +
>> +static int unmap_firmware_writeable(u64 *paddr, u32 len, bool guest, struct snp_host_map *map)
>> +{
>> + unsigned int npages = PAGE_ALIGN(len) >> PAGE_SHIFT;
>> +
>> + if (!map->active)
>> + return 0;
>> +
>> + /* If paddr points to a guest memory then restore the page state to hypervisor. */
>> + if (guest) {
>> + if (snp_reclaim_pages(*paddr, npages, true))
>> + return -EFAULT;
>> +
>> + goto done;
>> + }
>> +
>> + /*
>> + * Transition the pre-allocated buffer to hypervisor state before the access.
>> + *
>> + * This is because while changing the page state to firmware, the kernel unmaps
>> + * the pages from the direct map, and to restore the direct map the pages must
>> + * be transitioned back to the shared state.
>> + */
>> + if (snp_reclaim_pages(__pa(map->host), npages, true))
>> + return -EFAULT;
>> +
>> + /* Copy the response data firmware buffer to the callers buffer. */
>> + memcpy(__va(__sme_clr(map->paddr)), map->host, min_t(size_t, len, map->len));
>> + *paddr = map->paddr;
>> +
>> +done:
>> + map->active = false;
>> + return 0;
>> +}
>> +
>> +static bool sev_legacy_cmd_buf_writable(int cmd)
>> +{
>> + switch (cmd) {
>> + case SEV_CMD_PLATFORM_STATUS:
>> + case SEV_CMD_GUEST_STATUS:
>> + case SEV_CMD_LAUNCH_START:
>> + case SEV_CMD_RECEIVE_START:
>> + case SEV_CMD_LAUNCH_MEASURE:
>> + case SEV_CMD_SEND_START:
>> + case SEV_CMD_SEND_UPDATE_DATA:
>> + case SEV_CMD_SEND_UPDATE_VMSA:
>> + case SEV_CMD_PEK_CSR:
>> + case SEV_CMD_PDH_CERT_EXPORT:
>> + case SEV_CMD_GET_ID:
>> + case SEV_CMD_ATTESTATION_REPORT:
>> + return true;
>> + default:
>> + return false;
>> + }
>> +}
>> +
>> +#define prep_buffer(name, addr, len, guest, map) \
>> + func(&((typeof(name *))cmd_buf)->addr, ((typeof(name *))cmd_buf)->len, guest, map)
>> +
>> +static int __snp_cmd_buf_copy(int cmd, void *cmd_buf, bool to_fw, int fw_err)
>> +{
>> + int (*func)(u64 *paddr, u32 len, bool guest, struct snp_host_map *map);
>> + struct sev_device *sev = psp_master->sev_data;
>> + bool from_fw = !to_fw;
>> +
>> + /*
>> + * After the command is completed, change the command buffer memory to
>> + * hypervisor state.
>> + *
>> + * The immutable bit is automatically cleared by the firmware, so
>> + * no not need to reclaim the page.
>> + */
>> + if (from_fw && sev_legacy_cmd_buf_writable(cmd)) {
>> + if (rmp_mark_pages_shared(__pa(cmd_buf), 1))
>> + return -EFAULT;
>> +
>> + /* No need to go further if firmware failed to execute command. */
>> + if (fw_err)
>> + return 0;
>> + }
>> +
>> + if (to_fw)
>> + func = map_firmware_writeable;
>> + else
>> + func = unmap_firmware_writeable;
>> +
>> + /*
>> + * A command buffer may contains a system physical address. If the address
>> + * points to a host memory then use an intermediate firmware page otherwise
>> + * change the page state in the RMP table.
>> + */
>> + switch (cmd) {
>> + case SEV_CMD_PDH_CERT_EXPORT:
>> + if (prep_buffer(struct sev_data_pdh_cert_export, pdh_cert_address,
>> + pdh_cert_len, false, &sev->snp_host_map[0]))
>> + goto err;
>> + if (prep_buffer(struct sev_data_pdh_cert_export, cert_chain_address,
>> + cert_chain_len, false, &sev->snp_host_map[1]))
>> + goto err;
>> + break;
>> + case SEV_CMD_GET_ID:
>> + if (prep_buffer(struct sev_data_get_id, address, len,
>> + false, &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + case SEV_CMD_PEK_CSR:
>> + if (prep_buffer(struct sev_data_pek_csr, address, len,
>> + false, &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + case SEV_CMD_LAUNCH_UPDATE_DATA:
>> + if (prep_buffer(struct sev_data_launch_update_data, address, len,
>> + true, &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + case SEV_CMD_LAUNCH_UPDATE_VMSA:
>> + if (prep_buffer(struct sev_data_launch_update_vmsa, address, len,
>> + true, &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + case SEV_CMD_LAUNCH_MEASURE:
>> + if (prep_buffer(struct sev_data_launch_measure, address, len,
>> + false, &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + case SEV_CMD_LAUNCH_UPDATE_SECRET:
>> + if (prep_buffer(struct sev_data_launch_secret, guest_address, guest_len,
>> + true, &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + case SEV_CMD_DBG_DECRYPT:
>> + if (prep_buffer(struct sev_data_dbg, dst_addr, len, false,
>> + &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + case SEV_CMD_DBG_ENCRYPT:
>> + if (prep_buffer(struct sev_data_dbg, dst_addr, len, true,
>> + &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + case SEV_CMD_ATTESTATION_REPORT:
>> + if (prep_buffer(struct sev_data_attestation_report, address, len,
>> + false, &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + case SEV_CMD_SEND_START:
>> + if (prep_buffer(struct sev_data_send_start, session_address,
>> + session_len, false, &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + case SEV_CMD_SEND_UPDATE_DATA:
>> + if (prep_buffer(struct sev_data_send_update_data, hdr_address, hdr_len,
>> + false, &sev->snp_host_map[0]))
>> + goto err;
>> + if (prep_buffer(struct sev_data_send_update_data, trans_address,
>> + trans_len, false, &sev->snp_host_map[1]))
>> + goto err;
>> + break;
>> + case SEV_CMD_SEND_UPDATE_VMSA:
>> + if (prep_buffer(struct sev_data_send_update_vmsa, hdr_address, hdr_len,
>> + false, &sev->snp_host_map[0]))
>> + goto err;
>> + if (prep_buffer(struct sev_data_send_update_vmsa, trans_address,
>> + trans_len, false, &sev->snp_host_map[1]))
>> + goto err;
>> + break;
>> + case SEV_CMD_RECEIVE_UPDATE_DATA:
>> + if (prep_buffer(struct sev_data_receive_update_data, guest_address,
>> + guest_len, true, &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + case SEV_CMD_RECEIVE_UPDATE_VMSA:
>> + if (prep_buffer(struct sev_data_receive_update_vmsa, guest_address,
>> + guest_len, true, &sev->snp_host_map[0]))
>> + goto err;
>> + break;
>> + default:
>> + break;
>> + }
>> +
>> + /* The command buffer need to be in the firmware state. */
>> + if (to_fw && sev_legacy_cmd_buf_writable(cmd)) {
>> + if (rmp_mark_pages_firmware(__pa(cmd_buf), 1, true))
>> + return -EFAULT;
>> + }
>> +
>> + return 0;
>> +
>> +err:
>> + return -EINVAL;
>> +}
>> +
>> +static inline bool need_firmware_copy(int cmd)
>> +{
>> + struct sev_device *sev = psp_master->sev_data;
>> +
>> + /* After SNP is INIT'ed, the behavior of legacy SEV command is changed. */
>> + return ((cmd < SEV_CMD_SNP_INIT) && sev->snp_initialized) ? true : false;
>> +}
>> +
>> +static int snp_aware_copy_to_firmware(int cmd, void *data)
>> +{
>> + return __snp_cmd_buf_copy(cmd, data, true, 0);
>> +}
>> +
>> +static int snp_aware_copy_from_firmware(int cmd, void *data, int fw_err)
>> +{
>> + return __snp_cmd_buf_copy(cmd, data, false, fw_err);
>> +}
>> +
>> static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>> {
>> struct psp_device *psp = psp_master;
>> struct sev_device *sev;
>> unsigned int phys_lsb, phys_msb;
>> unsigned int reg, ret = 0;
>> + void *cmd_buf;
>> int buf_len;
>>
>> if (!psp || !psp->sev_data)
>> @@ -512,12 +819,28 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>> * work for some memory, e.g. vmalloc'd addresses, and @data may not be
>> * physically contiguous.
>> */
>> - if (data)
>> - memcpy(sev->cmd_buf, data, buf_len);
>> + if (data) {
>> + if (sev->cmd_buf_active > 2)
>> + return -EBUSY;
>> +
>> + cmd_buf = sev->cmd_buf_active ? sev->cmd_buf_backup : sev->cmd_buf;
>> +
>> + memcpy(cmd_buf, data, buf_len);
>> + sev->cmd_buf_active++;
>> +
>> + /*
>> + * The behavior of the SEV-legacy commands is altered when the
>> + * SNP firmware is in the INIT state.
>> + */
>> + if (need_firmware_copy(cmd) && snp_aware_copy_to_firmware(cmd, sev->cmd_buf))
> I believe this should be cmd_buf instead of sev->cmd_buf.
> snp_aware_copy_to_firmware(cmd, cmd_buf)
Yes, you are right, this should be cmd_buf instead of sev->cmd_buf, will
fix this accordingly.
Thanks,
Ashish
>
>> + return -EFAULT;
>> + } else {
>> + cmd_buf = sev->cmd_buf;
>> + }
>>
>> /* Get the physical address of the command buffer */
>> - phys_lsb = data ? lower_32_bits(__psp_pa(sev->cmd_buf)) : 0;
>> - phys_msb = data ? upper_32_bits(__psp_pa(sev->cmd_buf)) : 0;
>> + phys_lsb = data ? lower_32_bits(__psp_pa(cmd_buf)) : 0;
>> + phys_msb = data ? upper_32_bits(__psp_pa(cmd_buf)) : 0;
>>
>> dev_dbg(sev->dev, "sev command id %#x buffer 0x%08x%08x timeout %us\n",
>> cmd, phys_msb, phys_lsb, psp_timeout);
>> @@ -560,15 +883,24 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>> ret = sev_write_init_ex_file_if_required(cmd);
>> }
>>
>> - print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
>> - buf_len, false);
>> -
>> /*
>> * Copy potential output from the PSP back to data. Do this even on
>> * failure in case the caller wants to glean something from the error.
>> */
>> - if (data)
>> - memcpy(data, sev->cmd_buf, buf_len);
>> + if (data) {
>> + /*
>> + * Restore the page state after the command completes.
>> + */
>> + if (need_firmware_copy(cmd) &&
>> + snp_aware_copy_from_firmware(cmd, cmd_buf, ret))
>> + return -EFAULT;
>> +
>> + memcpy(data, cmd_buf, buf_len);
>> + sev->cmd_buf_active--;
>> + }
>> +
>> + print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,
>> + buf_len, false);
>>
>> return ret;
>> }
>> @@ -1579,10 +1911,12 @@ int sev_dev_init(struct psp_device *psp)
>> if (!sev)
>> goto e_err;
>>
>> - sev->cmd_buf = (void *)devm_get_free_pages(dev, GFP_KERNEL, 0);
>> + sev->cmd_buf = (void *)devm_get_free_pages(dev, GFP_KERNEL, 1);
>> if (!sev->cmd_buf)
>> goto e_sev;
>>
>> + sev->cmd_buf_backup = (uint8_t *)sev->cmd_buf + PAGE_SIZE;
>> +
>> psp->sev_data = sev;
>>
>> sev->dev = dev;
>> @@ -1648,6 +1982,12 @@ static void sev_firmware_shutdown(struct sev_device *sev)
>> snp_range_list = NULL;
>> }
>>
>> + /*
>> + * The host map need to clear the immutable bit so it must be free'd before the
>> + * SNP firmware shutdown.
>> + */
>> + free_snp_host_map(sev);
>> +
>> sev_snp_shutdown(&error);
>> }
>>
>> @@ -1722,6 +2062,14 @@ void sev_pci_init(void)
>> dev_err(sev->dev, "SEV-SNP: failed to INIT error %#x\n", error);
>> }
>> }
>> +
>> + /*
>> + * Allocate the intermediate buffers used for the legacy command handling.
>> + */
>> + if (alloc_snp_host_map(sev)) {
>> + dev_notice(sev->dev, "Failed to alloc host map (disabling legacy SEV)\n");
>> + goto skip_legacy;
>> + }
>> }
>>
>> /* Obtain the TMR memory area for SEV-ES use */
>> @@ -1739,12 +2087,14 @@ void sev_pci_init(void)
>> dev_err(sev->dev, "SEV: failed to INIT error %#x, rc %d\n",
>> error, rc);
>>
>> +skip_legacy:
>> dev_info(sev->dev, "SEV%s API:%d.%d build:%d\n", sev->snp_initialized ?
>> "-SNP" : "", sev->api_major, sev->api_minor, sev->build);
>>
>> return;
>>
>> err:
>> + free_snp_host_map(sev);
>> psp_master->sev_data = NULL;
>> }
>>
>> diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
>> index 34767657beb5..19d79f9d4212 100644
>> --- a/drivers/crypto/ccp/sev-dev.h
>> +++ b/drivers/crypto/ccp/sev-dev.h
>> @@ -29,11 +29,20 @@
>> #define SEV_CMDRESP_CMD_SHIFT 16
>> #define SEV_CMDRESP_IOC BIT(0)
>>
>> +#define MAX_SNP_HOST_MAP_BUFS 2
>> +
>> struct sev_misc_dev {
>> struct kref refcount;
>> struct miscdevice misc;
>> };
>>
>> +struct snp_host_map {
>> + u64 paddr;
>> + u32 len;
>> + void *host;
>> + bool active;
>> +};
>> +
>> struct sev_device {
>> struct device *dev;
>> struct psp_device *psp;
>> @@ -52,8 +61,11 @@ struct sev_device {
>> u8 build;
>>
>> void *cmd_buf;
>> + void *cmd_buf_backup;
>> + int cmd_buf_active;
>>
>> bool snp_initialized;
>> + struct snp_host_map snp_host_map[MAX_SNP_HOST_MAP_BUFS];
>> };
>>
>> int sev_dev_init(struct psp_device *psp);
>> --
>> 2.25.1
>>
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