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x86/compressed: Register GHCB memory when SEV-SNP is active

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The SEV-SNP guest is required by the GHCB spec to register the GHCB's
Guest Physical Address (GPA). This is because the hypervisor may prefer
that a guest use a consistent and/or specific GPA for the GHCB associated
with a vCPU. For more information, see the GHCB specification section
"GHCB GPA Registration".

If hypervisor can not work with the guest provided GPA then terminate the
guest boot.

Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Venu Busireddy <venu.busireddy@oracle.com>
Link: https://lore.kernel.org/r/20220307213356.2797205-17-brijesh.singh@amd.com
This commit is contained in:
Brijesh Singh 2022-02-09 12:10:10 -06:00 committed by Borislav Petkov
parent 4f9c403e44
commit 87294bdb7b
3 changed files with 33 additions and 0 deletions
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4
arch/x86/boot/compressed/sev.c
View file

@ -175,6 +175,10 @@ static bool early_setup_ghcb(void)
/* Initialize lookup tables for the instruction decoder */
inat_init_tables();
/* SNP guest requires the GHCB GPA must be registered */
if (sev_snp_enabled())
snp_register_ghcb_early(__pa(&boot_ghcb_page));
return true;
}

13
arch/x86/include/asm/sev-common.h
View file

@ -57,6 +57,19 @@
#define GHCB_MSR_AP_RESET_HOLD_REQ 0x006
#define GHCB_MSR_AP_RESET_HOLD_RESP 0x007
/* GHCB GPA Register */
#define GHCB_MSR_REG_GPA_REQ 0x012
#define GHCB_MSR_REG_GPA_REQ_VAL(v) \
/* GHCBData[63:12] */ \
(((u64)((v) & GENMASK_ULL(51, 0)) << 12) | \
/* GHCBData[11:0] */ \
GHCB_MSR_REG_GPA_REQ)
#define GHCB_MSR_REG_GPA_RESP 0x013
#define GHCB_MSR_REG_GPA_RESP_VAL(v) \
/* GHCBData[63:12] */ \
(((u64)(v) & GENMASK_ULL(63, 12)) >> 12)
/*
* SNP Page State Change Operation
*

16
arch/x86/kernel/sev-shared.c
View file

@ -68,6 +68,22 @@ static u64 get_hv_features(void)
return GHCB_MSR_HV_FT_RESP_VAL(val);
}
static void __maybe_unused snp_register_ghcb_early(unsigned long paddr)
{
unsigned long pfn = paddr >> PAGE_SHIFT;
u64 val;
sev_es_wr_ghcb_msr(GHCB_MSR_REG_GPA_REQ_VAL(pfn));
VMGEXIT();
val = sev_es_rd_ghcb_msr();
/* If the response GPA is not ours then abort the guest */
if ((GHCB_RESP_CODE(val) != GHCB_MSR_REG_GPA_RESP) ||
(GHCB_MSR_REG_GPA_RESP_VAL(val) != pfn))
sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_REGISTER);
}
static bool sev_es_negotiate_protocol(void)
{
u64 val;