linux-kernel - Re: [PATCH] KVM: X86: Fix SMRAM accessing even if VM is shutdown

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Date:   Fri, 9 Feb 2018 13:42:51 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Xiao Guangrong <guangrong.xiao@...il.com>,
        Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        Dmitry Vyukov <dvyukov@...gle.com>
Subject: Re: [PATCH] KVM: X86: Fix SMRAM accessing even if VM is shutdown

On 09/02/2018 04:22, Xiao Guangrong wrote:
>>
> 
> That is a good question... :)
> 
> This case (with KVM_MEMSLOT_INVALID is set) can be easily constructed,
> userspace should avoid this case by itself (avoiding vCPU accessing the
> memslot which is being updated). If it happens, it's a operation issue
> rather than INTERNAL ERROR.
> 
> Maybe treat it as MMIO accessing and return to userspace with MMIO_EXIT
> is a better solution...

Yeah, that's what emulation would do (except if it's an instruction
fetch, which will cause emulation to fail).  I think it's a bug in the
non-EPT #PF case that we return with -EFAULT.

Paolo