Re: [PATCH 1/2] KVM: x86: Emulate split-lock access as a write

[Andy Lutomirski]

> On Jan 30, 2020, at 4:31 AM, David Laight <David.Laight@xxxxxxxxxx> wrote:
> 
> ïFrom: Xiaoyao Li
>> Sent: 30 January 2020 12:20
>> If split lock detect is enabled (warn/fatal), #AC handler calls die()
>> when split lock happens in kernel.
>> 
>> A sane guest should never tigger emulation on a split-lock access, but
>> it cannot prevent malicous guest from doing this. So just emulating the
>> access as a write if it's a split-lock access to avoid malicous guest
>> polluting the kernel log.
> 
> That doesn't seem right if, for example, the locked access is addx.
> ISTM it would be better to force an immediate fatal error of some
> kind than just corrupt the guest memory.
> 
>    

The existing page-spanning case is just as wrong.