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The below subject line would be more appropriate: x86/sev: Allow IBPB-on-Entry feature for SNP guests > The SEV-SNP IBPB-on-Entry feature does not require a guest-side > implementation. The feature was added in Zen5 h/w, after the first > SNP Zen implementation, and thus was not accounted for when the > initial set of SNP features were added to the kernel. > > In its abundant precaution, commit 8c29f0165405 ("x86/sev: Add SEV-SNP > guest feature negotiation support") included SEV_STATUS' IBPB-on-Entry > bit as a reserved bit, thereby masking guests from using the feature. > > Unmask the bit, to allow guests to take advantage of the feature on > hypervisor kernel versions that support it: Amend the SEV_STATUS MSR > SNP_RESERVED_MASK to exclude bit 23 (IbpbOnEntry). > > Fixes: 8c29f0165405 ("x86/sev: Add SEV-SNP guest feature negotiation support")> Cc: Nikunj A Dadhania > Cc: Tom Lendacky > CC: Borislav Petkov (AMD) > CC: Michael Roth > Cc: stable@kernel.org > Signed-off-by: Kim Phillips Apart from the above comments: Reviewed-by: Nikunj A Dadhania > --- > arch/x86/boot/compressed/sev.c | 1 + > arch/x86/coco/sev/core.c | 1 + > arch/x86/include/asm/msr-index.h | 5 ++++- > 3 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c > index c8c1464b3a56..2b639703b8dd 100644 > --- a/arch/x86/boot/compressed/sev.c > +++ b/arch/x86/boot/compressed/sev.c > @@ -188,6 +188,7 @@ bool sev_es_check_ghcb_fault(unsigned long address) > MSR_AMD64_SNP_RESERVED_BIT13 | \ > MSR_AMD64_SNP_RESERVED_BIT15 | \ > MSR_AMD64_SNP_SECURE_AVIC | \ > + MSR_AMD64_SNP_RESERVED_BITS19_22 | \ > MSR_AMD64_SNP_RESERVED_MASK) > > #ifdef CONFIG_AMD_SECURE_AVIC > diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c > index 9ae3b11754e6..13f608117411 100644 > --- a/arch/x86/coco/sev/core.c > +++ b/arch/x86/coco/sev/core.c > @@ -122,6 +122,7 @@ static const char * const sev_status_feat_names[] = { > [MSR_AMD64_SNP_VMSA_REG_PROT_BIT] = "VMSARegProt", > [MSR_AMD64_SNP_SMT_PROT_BIT] = "SMTProt", > [MSR_AMD64_SNP_SECURE_AVIC_BIT] = "SecureAVIC", > + [MSR_AMD64_SNP_IBPB_ON_ENTRY_BIT] = "IBPBOnEntry", > }; > > /* > diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h > index 4d3566bb1a93..9016a6b00bc7 100644 > --- a/arch/x86/include/asm/msr-index.h > +++ b/arch/x86/include/asm/msr-index.h > @@ -735,7 +735,10 @@ > #define MSR_AMD64_SNP_SMT_PROT BIT_ULL(MSR_AMD64_SNP_SMT_PROT_BIT) > #define MSR_AMD64_SNP_SECURE_AVIC_BIT 18 > #define MSR_AMD64_SNP_SECURE_AVIC BIT_ULL(MSR_AMD64_SNP_SECURE_AVIC_BIT) > -#define MSR_AMD64_SNP_RESV_BIT 19 > +#define MSR_AMD64_SNP_RESERVED_BITS19_22 GENMASK_ULL(22, 19) > +#define MSR_AMD64_SNP_IBPB_ON_ENTRY_BIT 23 > +#define MSR_AMD64_SNP_IBPB_ON_ENTRY BIT_ULL(MSR_AMD64_SNP_IBPB_ON_ENTRY_BIT) > +#define MSR_AMD64_SNP_RESV_BIT 24 > #define MSR_AMD64_SNP_RESERVED_MASK GENMASK_ULL(63, MSR_AMD64_SNP_RESV_BIT) > #define MSR_AMD64_SAVIC_CONTROL 0xc0010138 > #define MSR_AMD64_SAVIC_EN_BIT 0