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Message-ID: <20240215000347.f2xtw3k3soqpd2c2@amd.com>
Date: Wed, 14 Feb 2024 18:03:47 -0600
From: Michael Roth <michael.roth@....com>
To: Paolo Bonzini <pbonzini@...hat.com>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
<seanjc@...gle.com>, <aik@....com>, <isaku.yamahata@...el.com>
Subject: Re: [PATCH 05/10] KVM: SEV: store VMSA features in kvm_sev_info
On Fri, Feb 09, 2024 at 01:37:37PM -0500, Paolo Bonzini wrote:
> Right now, the set of features that are stored in the VMSA upon
> initialization is fixed and depends on the module parameters for
> kvm-amd.ko. However, the hypervisor cannot really change it at will
> because the feature word has to match between the hypervisor and whatever
> computes a measurement of the VMSA for attestation purposes.
>
> Add a field to kvm_set_info that holds the set of features to be stored
s/kvm_set_info_/kvm_sev_info/
Otherwise:
Reviewed-by: Michael Roth <michael.roth@....com>
> in the VMSA; and query it instead of referring to the module parameters.
>
> Because KVM_SEV_INIT and KVM_SEV_ES_INIT accept no parameters, this
> does not yet introduce any functional change, but it paves the way for
> an API that allows customization of the features per-VM.
>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---
> arch/x86/kvm/svm/sev.c | 22 ++++++++++++++++++----
> arch/x86/kvm/svm/svm.c | 2 +-
> arch/x86/kvm/svm/svm.h | 3 ++-
> 3 files changed, 21 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 2e558f7538c2..712bfbc0028a 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -116,6 +116,14 @@ static inline bool is_mirroring_enc_context(struct kvm *kvm)
> return !!to_kvm_svm(kvm)->sev_info.enc_context_owner;
> }
>
> +static bool sev_vcpu_has_debug_swap(struct vcpu_svm *svm)
> +{
> + struct kvm_vcpu *vcpu = &svm->vcpu;
> + struct kvm_sev_info *sev = &to_kvm_svm(vcpu->kvm)->sev_info;
> +
> + return sev->vmsa_features & SVM_SEV_FEAT_DEBUG_SWAP;
> +}
> +
> /* Must be called with the sev_bitmap_lock held */
> static bool __sev_recycle_asids(int min_asid, int max_asid)
> {
> @@ -258,6 +266,8 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
>
> sev->active = true;
> sev->es_active = argp->id == KVM_SEV_ES_INIT;
> + sev->vmsa_features = sev_supported_vmsa_features;
> +
> asid = sev_asid_new(sev);
> if (asid < 0)
> goto e_no_asid;
> @@ -278,6 +288,7 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
> sev_asid_free(sev);
> sev->asid = 0;
> e_no_asid:
> + sev->vmsa_features = 0;
> sev->es_active = false;
> sev->active = false;
> return ret;
> @@ -572,6 +583,8 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
>
> static int sev_es_sync_vmsa(struct vcpu_svm *svm)
> {
> + struct kvm_vcpu *vcpu = &svm->vcpu;
> + struct kvm_sev_info *sev = &to_kvm_svm(vcpu->kvm)->sev_info;
> struct sev_es_save_area *save = svm->sev_es.vmsa;
>
> /* Check some debug related fields before encrypting the VMSA */
> @@ -613,7 +626,7 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
> save->xss = svm->vcpu.arch.ia32_xss;
> save->dr6 = svm->vcpu.arch.dr6;
>
> - save->sev_features = sev_supported_vmsa_features;
> + save->sev_features = sev->vmsa_features;
>
> pr_debug("Virtual Machine Save Area (VMSA):\n");
> print_hex_dump_debug("", DUMP_PREFIX_NONE, 16, 1, save, sizeof(*save), false);
> @@ -1693,6 +1706,7 @@ static void sev_migrate_from(struct kvm *dst_kvm, struct kvm *src_kvm)
> dst->pages_locked = src->pages_locked;
> dst->enc_context_owner = src->enc_context_owner;
> dst->es_active = src->es_active;
> + dst->vmsa_features = src->vmsa_features;
>
> src->asid = 0;
> src->active = false;
> @@ -3063,7 +3077,7 @@ static void sev_es_init_vmcb(struct vcpu_svm *svm)
> svm_set_intercept(svm, TRAP_CR8_WRITE);
>
> vmcb->control.intercepts[INTERCEPT_DR] = 0;
> - if (!sev_es_debug_swap_enabled) {
> + if (!sev_vcpu_has_debug_swap(svm)) {
> vmcb_set_intercept(&vmcb->control, INTERCEPT_DR7_READ);
> vmcb_set_intercept(&vmcb->control, INTERCEPT_DR7_WRITE);
> recalc_intercepts(svm);
> @@ -3118,7 +3132,7 @@ void sev_es_vcpu_reset(struct vcpu_svm *svm)
> sev_enc_bit));
> }
>
> -void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa)
> +void sev_es_prepare_switch_to_guest(struct vcpu_svm *svm, struct sev_es_save_area *hostsa)
> {
> /*
> * All host state for SEV-ES guests is categorized into three swap types
> @@ -3146,7 +3160,7 @@ void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa)
> * the CPU (Type-B). If DebugSwap is disabled/unsupported, the CPU both
> * saves and loads debug registers (Type-A).
> */
> - if (sev_es_debug_swap_enabled) {
> + if (sev_vcpu_has_debug_swap(svm)) {
> hostsa->dr0 = native_get_debugreg(0);
> hostsa->dr1 = native_get_debugreg(1);
> hostsa->dr2 = native_get_debugreg(2);
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index aa1792f402ab..392b9c2e2ce1 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -1523,7 +1523,7 @@ static void svm_prepare_switch_to_guest(struct kvm_vcpu *vcpu)
> struct sev_es_save_area *hostsa;
> hostsa = (struct sev_es_save_area *)(page_address(sd->save_area) + 0x400);
>
> - sev_es_prepare_switch_to_guest(hostsa);
> + sev_es_prepare_switch_to_guest(svm, hostsa);
> }
>
> if (tsc_scaling)
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index d630026b23b0..864c782eaa58 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -85,6 +85,7 @@ struct kvm_sev_info {
> unsigned long pages_locked; /* Number of pages locked */
> struct list_head regions_list; /* List of registered regions */
> u64 ap_jump_table; /* SEV-ES AP Jump Table address */
> + u64 vmsa_features;
> struct kvm *enc_context_owner; /* Owner of copied encryption context */
> struct list_head mirror_vms; /* List of VMs mirroring */
> struct list_head mirror_entry; /* Use as a list entry of mirrors */
> @@ -693,7 +694,7 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu);
> int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in);
> void sev_es_vcpu_reset(struct vcpu_svm *svm);
> void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector);
> -void sev_es_prepare_switch_to_guest(struct sev_es_save_area *hostsa);
> +void sev_es_prepare_switch_to_guest(struct vcpu_svm *svm, struct sev_es_save_area *hostsa);
> void sev_es_unmap_ghcb(struct vcpu_svm *svm);
>
> /* vmenter.S */
> --
> 2.39.0
>
>
>
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