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Subject: Re: [PATCH] KVM: x86: use positive error values for msr emulation
 that causes #GP
To:     Qian Cai <cai@redhat.com>, Maxim Levitsky <mlevitsk@redhat.com>,
        kvm@vger.kernel.org
Cc:     Borislav Petkov <bp@alien8.de>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@vger.kernel.org>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Joerg Roedel <joro@8bytes.org>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Ingo Molnar <mingo@redhat.com>
References: <20201101115523.115780-1-mlevitsk@redhat.com>
 <247d36e9a0f2b06c8a4008c634d008ef4403c579.camel@redhat.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <b24378fd-98d4-0231-3de4-3cc4f7d0e61c@redhat.com>
Date:   Wed, 4 Nov 2020 17:40:36 +0100
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On 04/11/20 17:31, Qian Cai wrote:
> On Sun, 2020-11-01 at 13:55 +0200, Maxim Levitsky wrote:
>> Recent introduction of the userspace msr filtering added code that uses
>> negative error codes for cases that result in either #GP delivery to
>> the guest, or handled by the userspace msr filtering.
>>
>> This breaks an assumption that a negative error code returned from the
>> msr emulation code is a semi-fatal error which should be returned
>> to userspace via KVM_RUN ioctl and usually kill the guest.
>>
>> Fix this by reusing the already existing KVM_MSR_RET_INVALID error code,
>> and by adding a new KVM_MSR_RET_FILTERED error code for the
>> userspace filtered msrs.
>>
>> Fixes: 291f35fb2c1d1 ("KVM: x86: report negative values from wrmsr emulation
>> to userspace")
>> Reported-by: Qian Cai <cai@redhat.com>
>> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
> Apparently, it does not apply cleanly on today's linux-next. Paolo, is it
> possible to toss this into -next soon, so our CI won't be blocked because of
> this bug?
> 

Yep, I plan to send it to Linus later this week.

Paolo