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Message-ID: <BYAPR21MB1688ACF3B9C9D48790128A48D750A@BYAPR21MB1688.namprd21.prod.outlook.com>
Date: Thu, 8 Jun 2023 14:21:46 +0000
From: "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To: Tianyu Lan <ltykernel@...il.com>,
KY Srinivasan <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
"wei.liu@...nel.org" <wei.liu@...nel.org>,
Dexuan Cui <decui@...rosoft.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"bp@...en8.de" <bp@...en8.de>,
"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
"x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
"arnd@...db.de" <arnd@...db.de>
CC: Tianyu Lan <Tianyu.Lan@...rosoft.com>,
"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"vkuznets@...hat.com" <vkuznets@...hat.com>
Subject: RE: [PATCH 4/9] drivers: hv: Mark shared pages unencrypted in SEV-SNP
enlightened guest
From: Tianyu Lan <ltykernel@...il.com> Sent: Thursday, June 1, 2023 8:16 AM
>
> Hypervisor needs to access iput arg, VMBus synic event and
s/iput/input/
> message pages. Mask these pages unencrypted in the sev-snp
s/Mask/Mark/
> guest and free them only if they have been marked encrypted
> successfully.
>
> Signed-off-by: Tianyu Lan <tiala@...rosoft.com>
> ---
> drivers/hv/hv.c | 57 +++++++++++++++++++++++++++++++++++++++---
> drivers/hv/hv_common.c | 24 +++++++++++++++++-
> 2 files changed, 77 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index de6708dbe0df..94406dbe0df0 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -20,6 +20,7 @@
> #include <linux/interrupt.h>
> #include <clocksource/hyperv_timer.h>
> #include <asm/mshyperv.h>
> +#include <linux/set_memory.h>
> #include "hyperv_vmbus.h"
>
> /* The one and only */
> @@ -78,7 +79,7 @@ int hv_post_message(union hv_connection_id connection_id,
>
> int hv_synic_alloc(void)
> {
> - int cpu;
> + int cpu, ret = -ENOMEM;
> struct hv_per_cpu_context *hv_cpu;
>
> /*
> @@ -123,26 +124,76 @@ int hv_synic_alloc(void)
> goto err;
> }
> }
> +
> + if (hv_isolation_type_en_snp()) {
> + ret = set_memory_decrypted((unsigned long)
> + hv_cpu->synic_message_page, 1);
> + if (ret) {
> + pr_err("Failed to decrypt SYNIC msg page: %d\n", ret);
> + hv_cpu->synic_message_page = NULL;
> +
> + /*
> + * Free the event page here and not encrypt
> + * the page in hv_synic_free().
> + */
Let's tweak the wording of the comment:
/*
* Free the event page here so that hv_synic_free()
* won't later try to re-encrypt it.
*/
> + free_page((unsigned long)hv_cpu->synic_event_page);
> + hv_cpu->synic_event_page = NULL;
> + goto err;
> + }
> +
> + ret = set_memory_decrypted((unsigned long)
> + hv_cpu->synic_event_page, 1);
> + if (ret) {
> + pr_err("Failed to decrypt SYNIC event page: %d\n", ret);
> + hv_cpu->synic_event_page = NULL;
> + goto err;
> + }
> +
> + memset(hv_cpu->synic_message_page, 0, PAGE_SIZE);
> + memset(hv_cpu->synic_event_page, 0, PAGE_SIZE);
> + }
> }
>
> return 0;
> +
> err:
> /*
> * Any memory allocations that succeeded will be freed when
> * the caller cleans up by calling hv_synic_free()
> */
> - return -ENOMEM;
> + return ret;
> }
>
>
> void hv_synic_free(void)
> {
> - int cpu;
> + int cpu, ret;
>
> for_each_present_cpu(cpu) {
> struct hv_per_cpu_context *hv_cpu
> = per_cpu_ptr(hv_context.cpu_context, cpu);
>
> + /* It's better to leak the page if the encryption fails. */
> + if (hv_isolation_type_en_snp()) {
> + if (hv_cpu->synic_message_page) {
> + ret = set_memory_encrypted((unsigned long)
> + hv_cpu->synic_message_page, 1);
> + if (ret) {
> + pr_err("Failed to encrypt SYNIC msg page: %d\n", ret);
> + hv_cpu->synic_message_page = NULL;
> + }
> + }
> +
> + if (hv_cpu->synic_event_page) {
> + ret = set_memory_encrypted((unsigned long)
> + hv_cpu->synic_event_page, 1);
> + if (ret) {
> + pr_err("Failed to encrypt SYNIC event page: %d\n", ret);
> + hv_cpu->synic_event_page = NULL;
> + }
> + }
> + }
> +
> free_page((unsigned long)hv_cpu->synic_event_page);
> free_page((unsigned long)hv_cpu->synic_message_page);
> }
> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
> index 179bc5f5bf52..bed9aa6ac19a 100644
> --- a/drivers/hv/hv_common.c
> +++ b/drivers/hv/hv_common.c
> @@ -24,6 +24,7 @@
> #include <linux/kmsg_dump.h>
> #include <linux/slab.h>
> #include <linux/dma-map-ops.h>
> +#include <linux/set_memory.h>
> #include <asm/hyperv-tlfs.h>
> #include <asm/mshyperv.h>
>
> @@ -359,6 +360,7 @@ int hv_common_cpu_init(unsigned int cpu)
> u64 msr_vp_index;
> gfp_t flags;
> int pgcount = hv_root_partition ? 2 : 1;
> + int ret;
>
> /* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
> flags = irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL;
> @@ -368,6 +370,17 @@ int hv_common_cpu_init(unsigned int cpu)
> if (!(*inputarg))
> return -ENOMEM;
>
> + if (hv_isolation_type_en_snp()) {
> + ret = set_memory_decrypted((unsigned long)*inputarg, pgcount);
> + if (ret) {
> + kfree(*inputarg);
> + *inputarg = NULL;
> + return ret;
> + }
> +
> + memset(*inputarg, 0x00, pgcount * PAGE_SIZE);
> + }
> +
> if (hv_root_partition) {
> outputarg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
> *outputarg = (char *)(*inputarg) + HV_HYP_PAGE_SIZE;
> @@ -387,7 +400,9 @@ int hv_common_cpu_die(unsigned int cpu)
> {
> unsigned long flags;
> void **inputarg, **outputarg;
> + int pgcount = hv_root_partition ? 2 : 1;
> void *mem;
> + int ret;
>
> local_irq_save(flags);
>
> @@ -402,7 +417,14 @@ int hv_common_cpu_die(unsigned int cpu)
>
> local_irq_restore(flags);
>
> - kfree(mem);
> + if (hv_isolation_type_en_snp()) {
> + ret = set_memory_encrypted((unsigned long)mem, pgcount);
> + if (ret)
> + pr_warn("Hyper-V: Failed to encrypt input arg on cpu%d: %d\n",
> + cpu, ret);
> + /* It's unsafe to free 'mem'. */
> + return 0;
> + }
>
> return 0;
> }
> --
> 2.25.1
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