From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vitaly Kuznetsov Subject: Re: [PATCH] KVM: x86: svm: report MSR_IA32_MCG_EXT_CTL as unsupported Date: Fri, 21 Dec 2018 11:06:52 +0100 Message-ID: <8736qrw5vn.fsf@vitty.brq.redhat.com> References: <20181219110613.24459-1-vkuznets@redhat.com> <20181220200630.GC25497@flask> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: kvm@vger.kernel.org, Paolo Bonzini , linux-kernel@vger.kernel.org, Tom Lendacky , Joerg Roedel , x86@kernel.org To: Radim =?utf-8?B?S3LEjW3DocWZ?= Return-path: In-Reply-To: <20181220200630.GC25497@flask> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org Radim Krčmář writes: > 2018-12-19 12:06+0100, Vitaly Kuznetsov: >> AMD doesn't seem to implement MSR_IA32_MCG_EXT_CTL and svm code in kvm >> knows nothing about it, however, this MSR is among emulated_msrs and >> thus returned with KVM_GET_MSR_INDEX_LIST. The consequent KVM_GET_MSRS, >> of course, fails. >> >> Report the MSR as unsupported to not confuse userspace. >> >> Signed-off-by: Vitaly Kuznetsov >> --- >> arch/x86/kvm/svm.c | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c >> index 2acb42b74a51..dfdf7d0b7f88 100644 >> --- a/arch/x86/kvm/svm.c >> +++ b/arch/x86/kvm/svm.c >> @@ -5845,6 +5845,13 @@ static bool svm_cpu_has_accelerated_tpr(void) >> >> static bool svm_has_emulated_msr(int index) >> { >> + switch (index) { >> + case MSR_IA32_MCG_EXT_CTL: >> + return false; >> + default: >> + break; > > Queued, thanks. > > Btw, I would prefer this without the > > default: break; > > as I don't think we'll ever add something there. "640K ought to be enough for anybody" :-) But in case you commit it as return index != MSR_IA32_MCG_EXT_CTL; I won't object. Thanks, -- Vitaly