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 bcca0b80e0d040be4ce9a4f9a2ee05d77e0c8257..9d2e0d547dafd42c67c665211f4d4b2aea75eff4 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5479,16 +5479,11 @@ 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;