From mboxrd@z Thu Jan 1 00:00:00 1970 From: Liran Alon Subject: Re: [PATCH v2 4/8] KVM: x86: Warn if userspace overrides existing injected exception/interrupt Date: Thu, 23 Nov 2017 00:27:46 +0200 Message-ID: <5A15F9E2.9090704@ORACLE.COM> References: <1511278211-12257-1-git-send-email-liran.alon@oracle.com> <1511278211-12257-5-git-send-email-liran.alon@oracle.com> <20171122203443.GA26792@flask> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Cc: pbonzini@redhat.com, kvm@vger.kernel.org, jmattson@google.com, wanpeng.li@hotmail.com, idan.brown@ORACLE.COM, Krish Sadhukhan To: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= Return-path: Received: from aserp1040.oracle.com ([141.146.126.69]:22014 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753045AbdKVW16 (ORCPT ); Wed, 22 Nov 2017 17:27:58 -0500 In-Reply-To: <20171122203443.GA26792@flask> Sender: kvm-owner@vger.kernel.org List-ID: On 22/11/17 22:34, Radim Krčmář wrote: > 2017-11-21 17:30+0200, Liran Alon: >> An alternative could have been done to return -EBUSY in this case. >> For now, we decided to just silently override exception and warn on >> such an attempt. >> >> Signed-off-by: Liran Alon >> Reviewed-by: Nikita Leshenko >> Reviewed-by: Krish Sadhukhan >> Signed-off-by: Krish Sadhukhan >> --- >> arch/x86/kvm/x86.c | 13 +++++++++++++ >> 1 file changed, 13 insertions(+) >> >> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c >> index 1490da89de4b..c8cec7c39c1c 100644 >> --- a/arch/x86/kvm/x86.c >> +++ b/arch/x86/kvm/x86.c >> @@ -3153,12 +3153,25 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu, >> return -EINVAL; >> >> process_nmi(vcpu); >> + >> + /* >> + * Warn if userspace is overriding existing >> + * injected exception >> + */ >> + WARN_ON_ONCE(vcpu->arch.exception.injected && >> + events->exception.injected); > > I think that overwriting the injected exception/interrupt is a perfectly > valid operation -- userspace could have rolled back the state to a time > of the previous injection. > > Syzkaller would complain sooner or later and I don't see it as a useful > printk, so dropping this patch would be preferred, > > thanks. > Hmm haven't thought about this use-case. I agree. This patch should be dropped from series. Thanks for spotting this. -Liran