KVM: nSVM: Optimize vmcb12 to vmcb02 save area copies

Use the vmcb12 control clean field to determine which vmcb12.save
registers were marked dirty in order to minimize register copies
when switching from L1 to L2. Those vmcb12 registers marked as dirty need
to be copied to L0's vmcb02 as they will be used to update the vmcb
state cache for the L2 VMRUN.  In the case where we have a different
vmcb12 from the last L2 VMRUN all vmcb12.save registers must be
copied over to L2.save.

Tested:
kvm-unit-tests
kvm selftests
Fedora L1 L2

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Cathy Avery <cavery@redhat.com>
Message-Id: <20210301200844.2000-1-cavery@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index c8ed267b76f07e2a79b13a35142ab40c2a9bb8d6..8523f60adb920ae2e6187a0e597e66c72b0fad6b 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -422,19 +422,31 @@ void nested_vmcb02_compute_g_pat(struct vcpu_svm *svm)
 
 static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12)
 {
+       bool new_vmcb12 = false;
+
        nested_vmcb02_compute_g_pat(svm);
 
        /* Load the nested guest state */
-       svm->vmcb->save.es = vmcb12->save.es;
-       svm->vmcb->save.cs = vmcb12->save.cs;
-       svm->vmcb->save.ss = vmcb12->save.ss;
-       svm->vmcb->save.ds = vmcb12->save.ds;
-       svm->vmcb->save.cpl = vmcb12->save.cpl;
-       vmcb_mark_dirty(svm->vmcb, VMCB_SEG);
 
-       svm->vmcb->save.gdtr = vmcb12->save.gdtr;
-       svm->vmcb->save.idtr = vmcb12->save.idtr;
-       vmcb_mark_dirty(svm->vmcb, VMCB_DT);
+       if (svm->nested.vmcb12_gpa != svm->nested.last_vmcb12_gpa) {
+               new_vmcb12 = true;
+               svm->nested.last_vmcb12_gpa = svm->nested.vmcb12_gpa;
+       }
+
+       if (unlikely(new_vmcb12 || vmcb_is_dirty(vmcb12, VMCB_SEG))) {
+               svm->vmcb->save.es = vmcb12->save.es;
+               svm->vmcb->save.cs = vmcb12->save.cs;
+               svm->vmcb->save.ss = vmcb12->save.ss;
+               svm->vmcb->save.ds = vmcb12->save.ds;
+               svm->vmcb->save.cpl = vmcb12->save.cpl;
+               vmcb_mark_dirty(svm->vmcb, VMCB_SEG);
+       }
+
+       if (unlikely(new_vmcb12 || vmcb_is_dirty(vmcb12, VMCB_DT))) {
+               svm->vmcb->save.gdtr = vmcb12->save.gdtr;
+               svm->vmcb->save.idtr = vmcb12->save.idtr;
+               vmcb_mark_dirty(svm->vmcb, VMCB_DT);
+       }
 
        kvm_set_rflags(&svm->vcpu, vmcb12->save.rflags | X86_EFLAGS_FIXED);
        svm_set_efer(&svm->vcpu, vmcb12->save.efer);
@@ -442,19 +454,22 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12
        svm_set_cr4(&svm->vcpu, vmcb12->save.cr4);
 
        svm->vcpu.arch.cr2 = vmcb12->save.cr2;
+
        kvm_rax_write(&svm->vcpu, vmcb12->save.rax);
        kvm_rsp_write(&svm->vcpu, vmcb12->save.rsp);
        kvm_rip_write(&svm->vcpu, vmcb12->save.rip);
 
        /* In case we don't even reach vcpu_run, the fields are not updated */
-       svm->vmcb->save.cr2 = svm->vcpu.arch.cr2;
        svm->vmcb->save.rax = vmcb12->save.rax;
        svm->vmcb->save.rsp = vmcb12->save.rsp;
        svm->vmcb->save.rip = vmcb12->save.rip;
 
-       svm->vmcb->save.dr7 = vmcb12->save.dr7 | DR7_FIXED_1;
-       svm->vcpu.arch.dr6  = vmcb12->save.dr6 | DR6_ACTIVE_LOW;
-       vmcb_mark_dirty(svm->vmcb, VMCB_DR);
+       /* These bits will be set properly on the first execution when new_vmc12 is true */
+       if (unlikely(new_vmcb12 || vmcb_is_dirty(vmcb12, VMCB_DR))) {
+               svm->vmcb->save.dr7 = vmcb12->save.dr7 | DR7_FIXED_1;
+               svm->vcpu.arch.dr6  = vmcb12->save.dr6 | DR6_ACTIVE_LOW;
+               vmcb_mark_dirty(svm->vmcb, VMCB_DR);
+       }
 }
 
 static void nested_vmcb02_prepare_control(struct vcpu_svm *svm)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 40e520a98fbc956b7be4dae0fa03d6d77c3c0b63..d5ee3bbcd0983f79b870cdcd2f6a668bd30d5059 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -1234,6 +1234,7 @@ static void init_vmcb(struct kvm_vcpu *vcpu)
        svm->asid = 0;
 
        svm->nested.vmcb12_gpa = 0;
+       svm->nested.last_vmcb12_gpa = 0;
        vcpu->arch.hflags = 0;
 
        if (!kvm_pause_in_guest(vcpu->kvm)) {

diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index c4a433c66a330867116fea3f0f7b738f7b5dc483..8e276c4fb33df758f70c48f4cef0ce3a1414c3dd 100644 (file)
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -93,6 +93,7 @@ struct svm_nested_state {
        u64 hsave_msr;
        u64 vm_cr_msr;
        u64 vmcb12_gpa;
+       u64 last_vmcb12_gpa;
 
        /* These are the merged vectors */
        u32 *msrpm;
@@ -247,6 +248,11 @@ static inline void vmcb_mark_dirty(struct vmcb *vmcb, int bit)
        vmcb->control.clean &= ~(1 << bit);
 }
 
+static inline bool vmcb_is_dirty(struct vmcb *vmcb, int bit)
+{
+        return !test_bit(bit, (unsigned long *)&vmcb->control.clean);
+}
+
 static inline struct vcpu_svm *to_svm(struct kvm_vcpu *vcpu)
 {
        return container_of(vcpu, struct vcpu_svm, vcpu);