[PATCH 5.11 106/601] KVM: nVMX: Truncate bits 63:32 of VMCS field on nested check in !64-bit

[Greg Kroah-Hartman]

From: Sean Christopherson <seanjc@xxxxxxxxxx>

commit ee050a577523dfd5fac95e6cc182ebe0293ead59 upstream.

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@xxxxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-Id: <20210422022128.3464144-6-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 arch/x86/kvm/vmx/nested.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5750,7 +5750,7 @@ static bool nested_vmx_exit_handled_vmcs
 
 	/* 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)