Re: [PATCH] KVM: nVMX: Don't expose TSC scaling to L1 when on Hyper-V

[Vitaly Kuznetsov]

Anirudh Rayabharam <anrayabh@xxxxxxxxxxxxxxxxxxx> writes:

> On Tue, Jun 14, 2022 at 07:20:34PM +0200, Paolo Bonzini wrote:
>> On 6/14/22 14:19, Vitaly Kuznetsov wrote:
>> > The latest version:
>> > https://docs.microsoft.com/en-us/virtualization/hyper-v-on-windows/tlfs/datatypes/hv_vmx_enlightened_vmcs
>> > 
>> > has it, actually. It was missing before (compare with e.g. 6.0b version
>> > here:
>> > https://github.com/MicrosoftDocs/Virtualization-Documentation/raw/live/tlfs/Hypervisor%20Top%20Level%20Functional%20Specification%20v6.0b.pdf)
>> > 
>> > but AFAIR TSC scaling wasn't advertised by genuine Hyper-V either.
>> > Interestingly enough, eVMCS version didn't change when these fields were
>> > added, it is still '1'.
>> > 
>> > I even have a patch in my stash (attached). I didn't send it out because
>> > it wasn't properly tested with different Hyper-V versions.
>> > 
>> > -- Vitaly
>> 
>> Anirudh, can you check if Vitaly's patches work for you?
>
> I will check it. But I wonder if they fit the criteria for inclusion in
> stable trees...
>
> It is important for the fix to land in the stable trees since this issue
> is a regression that was introduced _after_ 5.13. (I probably should've
> mentioned this in the changelog.)
>

Personally, I see no problem with splitting off TscMultiplier part from
my patch and marking it for stable@ fixing d041b5ea93352. I'm going to
run some tests too.

-- 
Vitaly