[PATCH 3/3] KVM: nVMX: remove unnecessary unload on processor-detected VMFail

[Paolo Bonzini]

nested_vmx_restore_host_state() is following a similar scheme to
load_vmcs12_host_state() which does not need a kvm_mmu_unload().
So, does nested_vmx_restore_host_state() need it?

The answer is no.  In the shadow case, kvm_init_mmu()
in nested_vmx_load_cr3() is enough to set a root_role
with guest_mode==0.  kvm_mmu_new_pgd() then is now
able to reuse an old root.  In the EPT case, root_mmu
still holds L1's valid root because L2 used guest_mmu.

Removing kvm_mmu_unload() thus is marginally more
efficient and it makes the two host state restore paths
identical.

The other thing that kvm_mmu_unload() does is clearing
the MMIO GVA cache.  This was ensured previously by
calling vcpu_clear_mmio_info() from kvm_mmu_load()
rather than just kvm_mmu_new_pgd().

Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
 arch/x86/kvm/vmx/nested.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index d612a5d071fc..8b20a5eac1c9 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4992,7 +4992,6 @@ static void nested_vmx_restore_host_state(struct kvm_vcpu *vcpu)
 	 * happen for VMFail, but we get here if the check was caught by
 	 * the processor and therefore the guest CR3 was loaded prematurely.
 	 */
-	kvm_mmu_unload(vcpu);
 	if (nested_vmx_load_cr3(vcpu, vmcs_readl(GUEST_CR3), false, !enable_ept, &ignored))
 		nested_vmx_abort(vcpu, VMX_ABORT_LOAD_HOST_PDPTE_FAIL);
 	if (enable_ept && is_pae_paging(vcpu))
-- 
2.52.0