On Fri, Feb 09, 2024 at 01:37:36PM -0500, Paolo Bonzini wrote:
> Compute the set of features to be stored in the VMSA when KVM is
> initialized; move it from there into kvm_sev_info when SEV is initialized,
> and then into the initial VMSA.
>
> The new variable can then be used to return the set of supported features
> to userspace, via the KVM_GET_DEVICE_ATTR ioctl.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---
> .../virt/kvm/x86/amd-memory-encryption.rst | 12 ++++++++++
> arch/x86/include/uapi/asm/kvm.h | 1 +
> arch/x86/kvm/svm/sev.c | 22 +++++++++++++++++--
> arch/x86/kvm/svm/svm.c | 1 +
> arch/x86/kvm/svm/svm.h | 1 +
> 5 files changed, 35 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
> index 37c5c37f4f6e..5ed11bc16b96 100644
> --- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst
> +++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst
> @@ -424,6 +424,18 @@ issued by the hypervisor to make the guest ready for execution.
>
> Returns: 0 on success, -negative on error
>
> +Device attribute API
> +====================
> +
> +Attributes of the SEV implementation can be retrieved through the
> +``KVM_HAS_DEVICE_ATTR`` and ``KVM_GET_DEVICE_ATTR`` ioctls on the ``/dev/kvm``
> +device node.
> +
> +Currently only one attribute is implemented:
> +
> +* group 0, attribute ``KVM_X86_SEV_VMSA_FEATURES``: return the set of all
> + bits that are accepted in the ``vmsa_features`` of ``KVM_SEV_INIT2``.
> +
> Firmware Management
> ===================
>
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index b305daff056e..cccaa5ff6d01 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -459,6 +459,7 @@ struct kvm_sync_regs {
>
> /* attributes for system fd (group 0) */
> #define KVM_X86_XCOMP_GUEST_SUPP 0
> +#define KVM_X86_SEV_VMSA_FEATURES 1
>
> struct kvm_vmx_nested_state_data {
> __u8 vmcs12[KVM_STATE_NESTED_VMX_VMCS_SIZE];
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index f760106c31f8..2e558f7538c2 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -65,6 +65,7 @@ module_param_named(debug_swap, sev_es_debug_swap_enabled, bool, 0444);
> #define sev_es_debug_swap_enabled false
> #endif /* CONFIG_KVM_AMD_SEV */
>
> +static u64 sev_supported_vmsa_features;
> static u8 sev_enc_bit;
> static DECLARE_RWSEM(sev_deactivate_lock);
> static DEFINE_MUTEX(sev_bitmap_lock);
...
> @@ -2276,6 +2290,10 @@ void __init sev_hardware_setup(void)
> if (!sev_es_enabled || !cpu_feature_enabled(X86_FEATURE_DEBUG_SWAP) ||
> !cpu_feature_enabled(X86_FEATURE_NO_NESTED_DATA_BP))
> sev_es_debug_swap_enabled = false;
> +
> + sev_supported_vmsa_features = 0;
This ^ seems unecessary. Otherwise:
Reviewed-by: Michael Roth <michael.roth@xxxxxxx>
> + if (sev_es_debug_swap_enabled)
> + sev_supported_vmsa_features |= SVM_SEV_FEAT_DEBUG_SWAP;
> #endif
> }
