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SubjectRe: [PATCH v2] x86/kvm: Disable KVM_ASYNC_PF_SEND_ALWAYS
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> On Apr 6, 2020, at 1:25 PM, Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Mon, Apr 06, 2020 at 03:09:51PM -0400, Vivek Goyal wrote:
>>> On Mon, Mar 09, 2020 at 09:22:15PM +0100, Peter Zijlstra wrote:
>>> On Mon, Mar 09, 2020 at 08:05:18PM +0100, Thomas Gleixner wrote:
>>>> Andy Lutomirski <luto@kernel.org> writes:
>>>
>>>>> I'm okay with the save/restore dance, I guess. It's just yet more
>>>>> entry crud to deal with architecture nastiness, except that this
>>>>> nastiness is 100% software and isn't Intel/AMD's fault.
>>>>
>>>> And we can do it in C and don't have to fiddle with it in the ASM
>>>> maze.
>>>
>>> Right; I'd still love to kill KVM_ASYNC_PF_SEND_ALWAYS though, even if
>>> we do the save/restore in do_nmi(). That is some wild brain melt. Also,
>>> AFAIK none of the distros are actually shipping a PREEMPT=y kernel
>>> anyway, so killing it shouldn't matter much.
>>
>> It will be nice if we can retain KVM_ASYNC_PF_SEND_ALWAYS. I have another
>> use case outside CONFIG_PREEMPT.
>>
>> I am trying to extend async pf interface to also report page fault errors
>> to the guest.
>
> Then please start over and design a sane ParaVirt Fault interface. The
> current one is utter crap.

Agreed. Don’t extend the current mechanism. Replace it.

I would be happy to review a replacement. I’m not really excited to review an extension of the current mess. The current thing is barely, if at all, correct.
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