[PATCH v2 5/9] KVM: nVMX: Truncate bits 63:32 of VMCS field on nested check in !64-bit

Sean Christopherson
2021-04-22T02:21:47Z

Drop bits 63:32 of the VMCS field encoding when checking for a nested
VM-Exit on VMREAD/VMWRITE in !64-bit mode. VMREAD and VMWRITE always
use 32-bit operands outside of 64-bit mode.

The actual emulation of VMREAD/VMWRITE does the right thing, this bug is
purely limited to incorrectly causing a nested VM-Exit if a GPR happens
to have bits 63:32 set outside of 64-bit mode.

Fixes: a7cde481b6e8 ("KVM: nVMX: Do not forward VMREAD/VMWRITE VMExits to L1 if required so by vmcs12 vmread/vmwrite bitmaps")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/nested.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 8b111682fe5c..0e580305a1ee 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5743,7 +5743,7 @@ static bool nested_vmx_exit_handled_vmcs_access(struct kvm_vcpu *vcpu,

/* Decode instruction info and find the field to access */
vmx_instruction_info = vmcs_read32(VMX_INSTRUCTION_INFO);
- field = kvm_register_read(vcpu, (((vmx_instruction_info) >> 28) & 0xf));
+ field = kvm_register_readl(vcpu, (((vmx_instruction_info) >> 28) & 0xf));

/* Out-of-range fields always cause a VM exit from L2 to L1 */
if (field >> 15)