[PATCH v4 3/3] KVM: SVM: use .prepare_guest_switch() to handle CPU register save/setup
From: Michael Roth
Date: Tue Feb 02 2021 - 14:07:04 EST
Currently we save host state like user-visible host MSRs, and do some
initial guest register setup for MSR_TSC_AUX and MSR_AMD64_TSC_RATIO
in svm_vcpu_load(). Defer this until just before we enter the guest by
moving the handling to kvm_x86_ops.prepare_guest_switch() similarly to
how it is done for the VMX implementation.
Additionally, since handling of saving/restoring host user MSRs is the
same both with/without SEV-ES enabled, move that handling to common
code.
Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
---
arch/x86/kvm/svm/sev.c | 22 +-----------
arch/x86/kvm/svm/svm.c | 76 +++++++++++++++++++++++++++++-------------
arch/x86/kvm/svm/svm.h | 5 +--
3 files changed, 56 insertions(+), 47 deletions(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 87167ef8ca23..874ea309279f 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2066,11 +2066,10 @@ void sev_es_create_vcpu(struct vcpu_svm *svm)
sev_enc_bit));
}
-void sev_es_vcpu_load(struct vcpu_svm *svm, int cpu)
+void sev_es_prepare_guest_switch(struct vcpu_svm *svm, unsigned int cpu)
{
struct svm_cpu_data *sd = per_cpu(svm_data, cpu);
struct vmcb_save_area *hostsa;
- unsigned int i;
/*
* As an SEV-ES guest, hardware will restore the host state on VMEXIT,
@@ -2079,13 +2078,6 @@ void sev_es_vcpu_load(struct vcpu_svm *svm, int cpu)
*/
vmsave(__sme_page_pa(sd->save_area));
- /*
- * Certain MSRs are restored on VMEXIT, only save ones that aren't
- * restored.
- */
- for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++)
- rdmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
-
/* XCR0 is restored on VMEXIT, save the current host value */
hostsa = (struct vmcb_save_area *)(page_address(sd->save_area) + 0x400);
hostsa->xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
@@ -2097,18 +2089,6 @@ void sev_es_vcpu_load(struct vcpu_svm *svm, int cpu)
hostsa->xss = host_xss;
}
-void sev_es_vcpu_put(struct vcpu_svm *svm)
-{
- unsigned int i;
-
- /*
- * Certain MSRs are restored on VMEXIT and were saved with vmsave in
- * sev_es_vcpu_load() above. Only restore ones that weren't.
- */
- for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++)
- wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
-}
-
void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector)
{
struct vcpu_svm *svm = to_svm(vcpu);
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index ae897aaa4471..0059f1d14b82 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1361,6 +1361,7 @@ static int svm_create_vcpu(struct kvm_vcpu *vcpu)
svm->vmsa = page_address(vmsa_page);
svm->asid_generation = 0;
+ svm->guest_state_loaded = false;
init_vmcb(svm);
svm_init_osvw(vcpu);
@@ -1408,23 +1409,30 @@ static void svm_free_vcpu(struct kvm_vcpu *vcpu)
__free_pages(virt_to_page(svm->msrpm), MSRPM_ALLOC_ORDER);
}
-static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+static void svm_prepare_guest_switch(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);
- struct svm_cpu_data *sd = per_cpu(svm_data, cpu);
- int i;
+ struct svm_cpu_data *sd = per_cpu(svm_data, vcpu->cpu);
+ unsigned int i;
- if (unlikely(cpu != vcpu->cpu)) {
- svm->asid_generation = 0;
- vmcb_mark_all_dirty(svm->vmcb);
- }
+ if (svm->guest_state_loaded)
+ return;
+
+ /*
+ * Certain MSRs are restored on VMEXIT (sev-es), or vmload of host save
+ * area (non-sev-es). Save ones that aren't so we can restore them
+ * individually later.
+ */
+ for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++)
+ rdmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
+ /*
+ * Save additional host state that will be restored on VMEXIT (sev-es)
+ * or subsequent vmload of host save area.
+ */
if (sev_es_guest(svm->vcpu.kvm)) {
- sev_es_vcpu_load(svm, cpu);
+ sev_es_prepare_guest_switch(svm, vcpu->cpu);
} else {
- for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++)
- rdmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
-
vmsave(__sme_page_pa(sd->save_area));
}
@@ -1435,10 +1443,42 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
wrmsrl(MSR_AMD64_TSC_RATIO, tsc_ratio);
}
}
+
/* This assumes that the kernel never uses MSR_TSC_AUX */
if (static_cpu_has(X86_FEATURE_RDTSCP))
wrmsrl(MSR_TSC_AUX, svm->tsc_aux);
+ svm->guest_state_loaded = true;
+}
+
+static void svm_prepare_host_switch(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_svm *svm = to_svm(vcpu);
+ unsigned int i;
+
+ if (!svm->guest_state_loaded)
+ return;
+
+ /*
+ * Certain MSRs are restored on VMEXIT (sev-es), or vmload of host save
+ * area (non-sev-es). Restore the ones that weren't.
+ */
+ for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++)
+ wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
+
+ svm->guest_state_loaded = false;
+}
+
+static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
+{
+ struct vcpu_svm *svm = to_svm(vcpu);
+ struct svm_cpu_data *sd = per_cpu(svm_data, cpu);
+
+ if (unlikely(cpu != vcpu->cpu)) {
+ svm->asid_generation = 0;
+ vmcb_mark_all_dirty(svm->vmcb);
+ }
+
if (sd->current_vmcb != svm->vmcb) {
sd->current_vmcb = svm->vmcb;
indirect_branch_prediction_barrier();
@@ -1448,18 +1488,10 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
static void svm_vcpu_put(struct kvm_vcpu *vcpu)
{
- struct vcpu_svm *svm = to_svm(vcpu);
- int i;
-
avic_vcpu_put(vcpu);
+ svm_prepare_host_switch(vcpu);
++vcpu->stat.host_state_reload;
- if (sev_es_guest(svm->vcpu.kvm)) {
- sev_es_vcpu_put(svm);
- } else {
- for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++)
- wrmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
- }
}
static unsigned long svm_get_rflags(struct kvm_vcpu *vcpu)
@@ -3614,10 +3646,6 @@ static void svm_flush_tlb_gva(struct kvm_vcpu *vcpu, gva_t gva)
invlpga(gva, svm->vmcb->control.asid);
}
-static void svm_prepare_guest_switch(struct kvm_vcpu *vcpu)
-{
-}
-
static inline void sync_cr8_to_lapic(struct kvm_vcpu *vcpu)
{
struct vcpu_svm *svm = to_svm(vcpu);
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 66d83dfefe18..cfc495c71fc1 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -172,6 +172,8 @@ struct vcpu_svm {
u64 ghcb_sa_len;
bool ghcb_sa_sync;
bool ghcb_sa_free;
+
+ bool guest_state_loaded;
};
struct svm_cpu_data {
@@ -570,9 +572,8 @@ int sev_handle_vmgexit(struct vcpu_svm *svm);
int sev_es_string_io(struct vcpu_svm *svm, int size, unsigned int port, int in);
void sev_es_init_vmcb(struct vcpu_svm *svm);
void sev_es_create_vcpu(struct vcpu_svm *svm);
-void sev_es_vcpu_load(struct vcpu_svm *svm, int cpu);
-void sev_es_vcpu_put(struct vcpu_svm *svm);
void sev_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector);
+void sev_es_prepare_guest_switch(struct vcpu_svm *svm, unsigned int cpu);
/* vmenter.S */
--
2.25.1