Commit 00f0b959 authored by Nikunj A Dadhania's avatar Nikunj A Dadhania Committed by Sean Christopherson
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KVM: SEV: Enforce minimum GHCB version requirement for SEV-SNP guests 



Require a minimum GHCB version of 2 when starting SEV-SNP guests through
KVM_SEV_INIT2. When a VMM attempts to start an SEV-SNP guest with an
incompatible GHCB version (less than 2), reject the request early rather
than allowing the guest kernel to start with an incorrect protocol version
and fail later with GHCB_SNP_UNSUPPORTED guest termination.

Not enforcing the minimum version typically causes the guest to request
termination with GHCB_SNP_UNSUPPORTED error code:

  kvm_amd: SEV-ES guest requested termination: 0x0:0x2

Fixes: 4af663c2 ("KVM: SEV: Allow per-guest configuration of GHCB protocol version")
Cc: Thomas Lendacky <thomas.lendacky@amd.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Michael Roth <michael.roth@amd.com>
Signed-off-by: default avatarNikunj A Dadhania <nikunj@amd.com>
Link: https://lore.kernel.org/r/20250819234833.3080255-3-seanjc@google.com


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent c78af203

arch/x86/kvm/svm/sev.c

+6 −2
Original line number Diff line number Diff line
@@ -405,6 +405,7 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp, 
	struct kvm_sev_info *sev = to_kvm_sev_info(kvm);

	struct sev_platform_init_args init_args = {0};

	bool es_active = vm_type != KVM_X86_SEV_VM;

	bool snp_active = vm_type == KVM_X86_SNP_VM;

	u64 valid_vmsa_features = es_active ? sev_supported_vmsa_features : 0;

	int ret;
@@ -428,6 +429,9 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp, 
	if (es_active && !data->ghcb_version)

		data->ghcb_version = 2;



	if (snp_active && data->ghcb_version < 2)

		return -EINVAL;



	if (unlikely(sev->active))

		return -EINVAL;
@@ -436,7 +440,7 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp, 
	sev->vmsa_features = data->vmsa_features;

	sev->ghcb_version = data->ghcb_version;



	if (vm_type == KVM_X86_SNP_VM)

	if (snp_active)

		sev->vmsa_features |= SVM_SEV_FEAT_SNP_ACTIVE;



	ret = sev_asid_new(sev);
@@ -454,7 +458,7 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp, 
	}



	/* This needs to happen after SEV/SNP firmware initialization. */

	if (vm_type == KVM_X86_SNP_VM) {

	if (snp_active) {

		ret = snp_guest_req_init(kvm);

		if (ret)

			goto e_free;