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KVM: nSVM: do not mark all VMCB02 fields dirty on nested vmexit
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Since L1 and L2 now use different VMCBs, most of the fields remain the
same in VMCB02 from one L2 run to the next.  Since KVM itself is not
looking at VMCB12's clean field, for now not much can be optimized.
However, in the future we could avoid more copies if the VMCB12's SEG
and DT sections are clean.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Paolo Bonzini committed Mar 15, 2021
1 parent 7ca62d1 commit 4bb170a
Showing 1 changed file with 12 additions and 6 deletions.
18 changes: 12 additions & 6 deletions arch/x86/kvm/svm/nested.c
Original file line number Diff line number Diff line change
Expand Up @@ -404,24 +404,32 @@ static void nested_vmcb02_prepare_save(struct vcpu_svm *svm, struct vmcb *vmcb12
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);

kvm_set_rflags(&svm->vcpu, vmcb12->save.rflags | X86_EFLAGS_FIXED);
svm_set_efer(&svm->vcpu, vmcb12->save.efer);
svm_set_cr0(&svm->vcpu, vmcb12->save.cr0);
svm_set_cr4(&svm->vcpu, vmcb12->save.cr4);
svm->vmcb->save.cr2 = svm->vcpu.arch.cr2 = vmcb12->save.cr2;

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;
svm->vmcb->save.cpl = vmcb12->save.cpl;
vmcb_mark_dirty(svm->vmcb, VMCB_DR);
}

static void nested_vmcb02_prepare_control(struct vcpu_svm *svm)
Expand Down Expand Up @@ -473,12 +481,10 @@ static void nested_vmcb02_prepare_control(struct vcpu_svm *svm)
enter_guest_mode(&svm->vcpu);

/*
* Merge guest and host intercepts - must be called with vcpu in
* guest-mode to take affect here
* Merge guest and host intercepts - must be called with vcpu in
* guest-mode to take effect.
*/
recalc_intercepts(svm);

vmcb_mark_all_dirty(svm->vmcb);
}

int enter_svm_guest_mode(struct vcpu_svm *svm, u64 vmcb12_gpa,
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