From 4af663c2f64a8d252e690c60cf8b8abf22dc2951 Mon Sep 17 00:00:00 2001 From: Michael Roth Date: Wed, 1 May 2024 02:10:48 -0500 Subject: [PATCH] KVM: SEV: Allow per-guest configuration of GHCB protocol version The GHCB protocol version may be different from one guest to the next. Add a field to track it for each KVM instance and extend KVM_SEV_INIT2 to allow it to be configured by userspace. Now that all SEV-ES support for GHCB protocol version 2 is in place, go ahead and default to it when creating SEV-ES guests through the new KVM_SEV_INIT2 interface. Keep the older KVM_SEV_ES_INIT interface restricted to GHCB protocol version 1. Suggested-by: Sean Christopherson Signed-off-by: Michael Roth Message-ID: <20240501071048.2208265-5-michael.roth@amd.com> Signed-off-by: Paolo Bonzini --- .../virt/kvm/x86/amd-memory-encryption.rst | 11 +++++-- arch/x86/include/uapi/asm/kvm.h | 4 ++- arch/x86/kvm/svm/sev.c | 32 +++++++++++++++++-- arch/x86/kvm/svm/svm.h | 1 + 4 files changed, 42 insertions(+), 6 deletions(-) diff --git a/Documentation/virt/kvm/x86/amd-memory-encryption.rst b/Documentation/virt/kvm/x86/amd-memory-encryption.rst index 3381556d596d..9677a0714a39 100644 --- a/Documentation/virt/kvm/x86/amd-memory-encryption.rst +++ b/Documentation/virt/kvm/x86/amd-memory-encryption.rst @@ -95,13 +95,19 @@ Returns: 0 on success, -negative on error struct kvm_sev_init { __u64 vmsa_features; /* initial value of features field in VMSA */ __u32 flags; /* must be 0 */ - __u32 pad[9]; + __u16 ghcb_version; /* maximum guest GHCB version allowed */ + __u16 pad1; + __u32 pad2[8]; }; It is an error if the hypervisor does not support any of the bits that are set in ``flags`` or ``vmsa_features``. ``vmsa_features`` must be 0 for SEV virtual machines, as they do not have a VMSA. +``ghcb_version`` must be 0 for SEV virtual machines, as they do not issue GHCB +requests. If ``ghcb_version`` is 0 for any other guest type, then the maximum +allowed guest GHCB protocol will default to version 2. + This command replaces the deprecated KVM_SEV_INIT and KVM_SEV_ES_INIT commands. The commands did not have any parameters (the ```data``` field was unused) and only work for the KVM_X86_DEFAULT_VM machine type (0). @@ -112,7 +118,8 @@ They behave as if: KVM_SEV_ES_INIT * the ``flags`` and ``vmsa_features`` fields of ``struct kvm_sev_init`` are - set to zero + set to zero, and ``ghcb_version`` is set to 0 for KVM_SEV_INIT and 1 for + KVM_SEV_ES_INIT. If the ``KVM_X86_SEV_VMSA_FEATURES`` attribute does not exist, the hypervisor only supports KVM_SEV_INIT and KVM_SEV_ES_INIT. In that case, note that KVM_SEV_ES_INIT diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h index 72ad5ace118d..9fae1b73b529 100644 --- a/arch/x86/include/uapi/asm/kvm.h +++ b/arch/x86/include/uapi/asm/kvm.h @@ -711,7 +711,9 @@ struct kvm_sev_cmd { struct kvm_sev_init { __u64 vmsa_features; __u32 flags; - __u32 pad[9]; + __u16 ghcb_version; + __u16 pad1; + __u32 pad2[8]; }; struct kvm_sev_launch_start { diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c index 01baa8aa7e12..a4bde1193b92 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -33,7 +33,8 @@ #include "cpuid.h" #include "trace.h" -#define GHCB_VERSION_MAX 1ULL +#define GHCB_VERSION_MAX 2ULL +#define GHCB_VERSION_DEFAULT 2ULL #define GHCB_VERSION_MIN 1ULL #define GHCB_HV_FT_SUPPORTED GHCB_HV_FT_SNP @@ -268,12 +269,24 @@ static int __sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp, if (data->vmsa_features & ~valid_vmsa_features) return -EINVAL; + if (data->ghcb_version > GHCB_VERSION_MAX || (!es_active && data->ghcb_version)) + return -EINVAL; + if (unlikely(sev->active)) return -EINVAL; sev->active = true; sev->es_active = es_active; sev->vmsa_features = data->vmsa_features; + sev->ghcb_version = data->ghcb_version; + + /* + * Currently KVM supports the full range of mandatory features defined + * by version 2 of the GHCB protocol, so default to that for SEV-ES + * guests created via KVM_SEV_INIT2. + */ + if (sev->es_active && !sev->ghcb_version) + sev->ghcb_version = GHCB_VERSION_DEFAULT; ret = sev_asid_new(sev); if (ret) @@ -307,6 +320,7 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp) { struct kvm_sev_init data = { .vmsa_features = 0, + .ghcb_version = 0, }; unsigned long vm_type; @@ -314,6 +328,14 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp) return -EINVAL; vm_type = (argp->id == KVM_SEV_INIT ? KVM_X86_SEV_VM : KVM_X86_SEV_ES_VM); + + /* + * KVM_SEV_ES_INIT has been deprecated by KVM_SEV_INIT2, so it will + * continue to only ever support the minimal GHCB protocol version. + */ + if (vm_type == KVM_X86_SEV_ES_VM) + data.ghcb_version = GHCB_VERSION_MIN; + return __sev_guest_init(kvm, argp, &data, vm_type); } @@ -2897,6 +2919,7 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm) { struct vmcb_control_area *control = &svm->vmcb->control; struct kvm_vcpu *vcpu = &svm->vcpu; + struct kvm_sev_info *sev = &to_kvm_svm(vcpu->kvm)->sev_info; u64 ghcb_info; int ret = 1; @@ -2907,7 +2930,7 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm) switch (ghcb_info) { case GHCB_MSR_SEV_INFO_REQ: - set_ghcb_msr(svm, GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX, + set_ghcb_msr(svm, GHCB_MSR_SEV_INFO((__u64)sev->ghcb_version, GHCB_VERSION_MIN, sev_enc_bit)); break; @@ -3268,11 +3291,14 @@ void sev_init_vmcb(struct vcpu_svm *svm) void sev_es_vcpu_reset(struct vcpu_svm *svm) { + struct kvm_vcpu *vcpu = &svm->vcpu; + struct kvm_sev_info *sev = &to_kvm_svm(vcpu->kvm)->sev_info; + /* * Set the GHCB MSR value as per the GHCB specification when emulating * vCPU RESET for an SEV-ES guest. */ - set_ghcb_msr(svm, GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX, + set_ghcb_msr(svm, GHCB_MSR_SEV_INFO((__u64)sev->ghcb_version, GHCB_VERSION_MIN, sev_enc_bit)); } diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index 6fd0f5862681..9ae0c57c7d20 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -87,6 +87,7 @@ struct kvm_sev_info { struct list_head regions_list; /* List of registered regions */ u64 ap_jump_table; /* SEV-ES AP Jump Table address */ u64 vmsa_features; + u16 ghcb_version; /* Highest guest GHCB protocol version allowed */ 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 */