linux-kernel - Re: [PATCH v5 3/3] KVM: nVMX: Fix mmu context after VMLAUNCH/VMRESUME failure

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Date:   Thu, 9 Nov 2017 11:40:14 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>, Jim Mattson <jmattson@...gle.com>
Cc:     Krish Sadhukhan <krish.sadhukhan@...cle.com>,
        LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH v5 3/3] KVM: nVMX: Fix mmu context after VMLAUNCH/VMRESUME
 failure

On 09/11/2017 01:37, Wanpeng Li wrote:
> 2017-11-09 5:47 GMT+08:00 Jim Mattson <jmattson@...gle.com>:
>> I realize now that there are actually many other problems with
>> deferring some control field checks to the hardware VM-entry of
>> vmcs02. When there is an invalid control field, the vCPU should just
>> fall through to the next instruction, without any state modifiation
>> other than the ALU flags and the VM-instruction error field of the
>> current VMCS. However, in preparation for the hardware VM-entry of
>> vmcs02, we have already changed quite a bit of the vCPU state: the
>> MSRs on the VM-entry MSR-load list, DR7, IA32_DEBUGCTL, the entire
>> FLAGS register, etc. All of these changes should be undone, and we're
>> not prepared to do that. (For instance, what was the old DR7 value
>> that needs to be restored?)
> I didn't observe real issue currently, and I hope this patchset can
> catch the upcoming merge window. Then we can dig more into your
> concern.

Can any of you write a simple testcase for just one bug (e.g. DR7)?

Thanks,

Paolo