KVM: SEV:
On Tue, Mar 03, 2026, Tycho Andersen wrote:
> From: "Tycho Andersen (AMD)" <tycho@kernel.org>
>
> Commit 0aa6b90ef9d7 ("KVM: SVM: Add support for allowing zero SEV ASIDs")
> made it possible to make it impossible to use SEV VMs by not allocating
> them any ASIDs.
>
> Commit 6c7c620585c6 ("KVM: SEV: Add SEV-SNP CipherTextHiding support") did
> the same thing for SEV-ES.
>
> Do not export KVM_X86_SEV(_ES)_VM as exported types if in either of these
^^^^^^^^
supported
> situations, so that userspace can use them to determine what is actually
> supported by the current kernel configuration.
>
> Also move the buildup to a local variable so it is easier to add additional
> masking in future patches.
>
> Link: https://lore.kernel.org/all/aZyLIWtffvEnmtYh@google.com/
> Suggested-by: Sean Christopherson <seanjc@google.com>
> Signed-off-by: Tycho Andersen (AMD) <tycho@kernel.org>
> ---
> arch/x86/kvm/svm/sev.c | 14 +++++++++++---
> 1 file changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 3f9c1aa39a0a..f941d48626d3 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -2957,18 +2957,26 @@ void sev_vm_destroy(struct kvm *kvm)
>
> void __init sev_set_cpu_caps(void)
> {
> + int supported_vm_types = 0;
This should be a u32.
> +
> if (sev_enabled) {
> kvm_cpu_cap_set(X86_FEATURE_SEV);
> - kvm_caps.supported_vm_types |= BIT(KVM_X86_SEV_VM);
> +
> + if (min_sev_asid <= max_sev_asid)
> + supported_vm_types |= BIT(KVM_X86_SEV_VM);
> }
> if (sev_es_enabled) {
> kvm_cpu_cap_set(X86_FEATURE_SEV_ES);
> - kvm_caps.supported_vm_types |= BIT(KVM_X86_SEV_ES_VM);
> +
> + if (min_sev_es_asid <= max_sev_es_asid)
> + supported_vm_types |= BIT(KVM_X86_SEV_ES_VM);
> }
> if (sev_snp_enabled) {
> kvm_cpu_cap_set(X86_FEATURE_SEV_SNP);
> - kvm_caps.supported_vm_types |= BIT(KVM_X86_SNP_VM);
> + supported_vm_types |= BIT(KVM_X86_SNP_VM);
> }
> +
> + kvm_caps.supported_vm_types |= supported_vm_types;
> }
>
> static bool is_sev_snp_initialized(void)
> --
> 2.53.0
>