Re: [PATCH v2] Fix undefined operation VMXOFF during reboot and crash

[David P. Reed]

On Monday, June 29, 2020 5:49pm, "Sean Christopherson" <sean.j.christopherson@xxxxxxxxx> said:

> On Mon, Jun 29, 2020 at 02:22:45PM -0700, Andy Lutomirski wrote:
>>
>>
>> > On Jun 29, 2020, at 1:54 PM, David P. Reed <dpreed@xxxxxxxxxxxx> wrote:
>> >
>> > ïSimple question for those on the To: and CC: list here. Should I
>> > abandon any hope of this patch being accepted? It's been a long time.
>> >
>> > The non-response after I acknowledged that this was discovered by when
>> > working on a personal, non-commercial research project - which is
>> > "out-of-tree" (apparently dirty words on LKML) has me thinking my
>> > contribution is unwanted. That's fine, I suppose. I can maintain this patch
>> > out-of-tree as well.  I did incorporate all the helpful suggestions I
>> > received in this second patch, and given some encouragement, will happily
>> > submit a revised v3 if there is any likelihood of acceptance. I'm wary of
>> > doing more radical changes (like combining emergency and normal paths).
>> >
>>
>> Sorry about being slow and less actively encouraging than we should be. We
>> absolutely welcome personal contributions. The actual problem is that
>> everyone is worked and weâre all slow. Also, you may be hitting a corner
>> case
>> in the process: is this a KVM patch or an x86 patch?
> 
> It's an x86 patch as it's not KVM specific, e.g. this code also helps play
> nice with out of tree hypervisors.
> 
> The code change is mostly good, but it needs to be split up as there are
> three separate fixes:
> 
>   1. Handle #UD on VMXON due to a race.
>   2. Mark memory and flags as clobbered by VMXON.
>   3. Change emergency_vmx_disable_all() to not manually check cpu_vmx_enabled().
> 
> Yes, the changes are tiny, but if for example #3 introduces a bug then we
> don't have to revert #1 and #2.  Or perhaps older kernels are only subject
> to the #1 and #2 and thus dumping all three changes into a single patch makes
> it all harder to backport.  In other words, all the usual "one change per
> patch" reasons.
> 
Thanks. If no one else responds with additional suggestions, I will make it into 3 patches.
I'm happy to learn the nuances of the kernel patch regimen.