Commit 2368048b authored by Sean Christopherson's avatar Sean Christopherson
Browse files

KVM: x86: Signal #GP, not -EPERM, on bad WRMSR(MCi_CTL/STATUS) 



Return '1', not '-1', when handling an illegal WRMSR to a MCi_CTL or
MCi_STATUS MSR.  The behavior of "all zeros' or "all ones" for CTL MSRs
is architectural, as is the "only zeros" behavior for STATUS MSRs.  I.e.
the intent is to inject a #GP, not exit to userspace due to an unhandled
emulation case.  Returning '-1' gets interpreted as -EPERM up the stack
and effecitvely kills the guest.

Fixes: 890ca9ae ("KVM: Add MCE support")
Fixes: 9ffd986c ("KVM: X86: #GP when guest attempts to write MCi_STATUS register w/o 0")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Reviewed-by: default avatarJim Mattson <jmattson@google.com>
Link: https://lore.kernel.org/r/20220512222716.4112548-2-seanjc@google.com
parent 03787394

arch/x86/kvm/x86.c

+2 −2
Original line number Diff line number Diff line
@@ -3239,13 +3239,13 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info) 
			 */

			if ((offset & 0x3) == 0 &&

			    data != 0 && (data | (1 << 10) | 1) != ~(u64)0)

				return -1;

				return 1;



			/* MCi_STATUS */

			if (!msr_info->host_initiated &&

			    (offset & 0x3) == 1 && data != 0) {

				if (!can_set_mci_status(vcpu))

					return -1;

					return 1;

			}



			vcpu->arch.mce_banks[offset] = data;