[PATCH v3 8/9] KVM: nSVM: use nested_svm_load_cr3() on guest->host switch

Vitaly Kuznetsov
2020-07-09T14:54:44Z

Make nSVM code resemble nVMX where nested_vmx_load_cr3() is used on
both guest->host and host->guest transitions. Also, we can now
eliminate unconditional kvm_mmu_reset_context() and speed things up.

Note, nVMX has two different paths: load_vmcs12_host_state() and
nested_vmx_restore_host_state() and the later is used to restore from
'partial' switch to L2, it always uses kvm_mmu_reset_context().
nSVM doesn't have this yet. Also, nested_svm_vmexit()'s return value
is almost always ignored nowadays.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/kvm/svm/nested.c | 15 ++++++---------
1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 5ddf20941cf9..9a137d3b3a1c 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -317,7 +317,7 @@ static inline bool nested_npt_enabled(struct vcpu_svm *svm)
}

/*
- * Load guest's cr3 at nested entry. @nested_npt is true if we are
+ * Load guest's/host's cr3 at nested entry. @nested_npt is true if we are
* emulating VM-Entry into a guest with NPT enabled.
*/
static int nested_svm_load_cr3(struct kvm_vcpu *vcpu, unsigned long cr3,
@@ -658,15 +658,12 @@ int nested_svm_vmexit(struct vcpu_svm *svm)

nested_svm_uninit_mmu_context(&svm->vcpu);

- if (npt_enabled) {
- svm->vmcb->save.cr3 = hsave->save.cr3;
- svm->vcpu.arch.cr3 = hsave->save.cr3;
- } else {
- (void)kvm_set_cr3(&svm->vcpu, hsave->save.cr3);
- }
+ rc = nested_svm_load_cr3(&svm->vcpu, hsave->save.cr3, false);
+ if (rc)
+ return 1;

- kvm_mmu_reset_context(&svm->vcpu);
- kvm_mmu_load(&svm->vcpu);
+ if (npt_enabled)
+ svm->vmcb->save.cr3 = hsave->save.cr3;

/*
* Drop what we picked up for L2 via svm_complete_interrupts() so it
--
2.25.4