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_sev_info that holds the set of features to be stored
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@xxxxxxxxxx>
Message-Id: <20240209183743.22030-6-pbonzini@xxxxxxxxxx>
Reviewed-by: Michael Roth <michael.roth@xxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/svm/sev.c | 29 +++++++++++++++++++++--------
arch/x86/kvm/svm/svm.c | 2 +-
arch/x86/kvm/svm/svm.h | 3 ++-
3 files changed, 24 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 22c35a39c25f..a8300646a280 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -96,6 +96,14 @@ 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(unsigned int min_asid, unsigned int max_asid)
{
@@ -245,6 +253,11 @@ 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;
+ if (sev_supported_vmsa_features)
+ pr_warn_once("Enabling DebugSwap with KVM_SEV_ES_INIT. "
+ "This will not work starting with Linux 6.10\n");
+
ret = sev_asid_new(sev);
if (ret)
goto e_no_asid;
@@ -266,6 +279,7 @@ 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;
@@ -560,6 +574,8 @@ 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 */
@@ -601,11 +617,7 @@ static int sev_es_sync_vmsa(struct vcpu_svm *svm)
save->xss = svm->vcpu.arch.ia32_xss;
save->dr6 = svm->vcpu.arch.dr6;
- if (sev_supported_vmsa_features) {
- save->sev_features = sev_supported_vmsa_features;
- pr_warn_once("Enabling DebugSwap with KVM_SEV_ES_INIT. "
- "This will not work starting with Linux 6.10\n");
- }
+ 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);
@@ -1685,6 +1697,7 @@ 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;
@@ -3057,7 +3070,7 @@ 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);
@@ -3112,7 +3125,7 @@ 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
@@ -3140,7 +3153,7 @@ 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 450535d6757f..c22e87ebf0de 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 864fac367424..b7707514d042 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 */
@@ -684,7 +685,7 @@ 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);
/* These symbols are used in common code and are stubbed below. */
--
2.43.0
