KVM: nVMX: Defer the MMU reload to the normal path on an EPTP switch

commit c805f5d5585ab5e0cdac6b1ccf7086eb120fb7db upstream.

Defer reloading the MMU after a EPTP successful EPTP switch.  The VMFUNC
instruction itself is executed in the previous EPTP context, any side
effects, e.g. updating RIP, should occur in the old context.  Practically
speaking, this bug is benign as VMX doesn't touch the MMU when skipping
an emulated instruction, nor does queuing a single-step #DB.  No other
post-switch side effects exist.

Fixes: 41ab93727467 ("KVM: nVMX: Emulate EPTP switching for the L1 hypervisor")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-14-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 15532feb19f103a4c96449f1ab272d1cc7864c99..bce4f0cd95119295e9b72e88f1cac91bda7605ea 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5491,16 +5491,11 @@ static int nested_vmx_eptp_switching(struct kvm_vcpu *vcpu,
                if (!nested_vmx_check_eptp(vcpu, new_eptp))
                        return 1;
 
-               kvm_mmu_unload(vcpu);
                mmu->ept_ad = accessed_dirty;
                mmu->mmu_role.base.ad_disabled = !accessed_dirty;
                vmcs12->ept_pointer = new_eptp;
-               /*
-                * TODO: Check what's the correct approach in case
-                * mmu reload fails. Currently, we just let the next
-                * reload potentially fail
-                */
-               kvm_mmu_reload(vcpu);
+
+               kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
        }
 
        return 0;