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

stable inclusion
from stable-5.10.37
commit fa9b4ee318f9a9ede1ada05ae170b500426ce6ec
bugzilla: 51868
CVE: NA

--------------------------------

commit c805f5d5 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: 41ab9372 ("KVM: nVMX: Emulate EPTP switching for the L1 hypervisor")
Cc: stable@vger.kernel.org
Signed-off-by: NSean Christopherson <seanjc@google.com>
Message-Id: <20210305011101.3597423-14-seanjc@google.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

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;