[Pkg-xen-devel] Bug#1020787: Bug#1020787: linux-image-5.19.0-2-amd64: After updating to 5.19 kernel the VMs are started without XSAVE CPU flags

[Diederik de Haas]

Hi Marek,

On dinsdag 27 september 2022 02:16:31 CEST Marek Marczykowski-Górecki wrote:
> On Tue, Sep 27, 2022 at 01:39:46AM +0200, Diederik de Haas wrote:
> > In kernel 5.19 the following commits were added under
> > ``arch/x86/kernel/fpu/``:
> > 
> > b91c0922bf1ed15b67a6faa404bc64e3ed532ec2 x86/fpu: Cleanup variable
> > shadowing 
> > 8ad7e8f696951f192c6629a0cbda9ac94c773159 x86/fpu/xsave: Support
> > XSAVEC in the kernel 
> > f5c0b4f30416c670408a77be94703d04d22b57df x86/prctl:
> > Remove pointless task argument

8ad7e8f696951f192c6629a0cbda9ac94c773159 seems to be the 'offending' commit ...

> > Also found this patch which should make the error msg more informative ...
> > https://lore.kernel.org/all/20220810221909.12768-1-andrew.cooper3@citrix.c
> > om/ Even though I haven't experienced it (yet?), the language of this
> > patch seems to indicate you're not alone with it.
> 
> There is also Xen patch fixing the issue:
> https://lore.kernel.org/xen-devel/a4ec41e6-16cd-4452-19c1-5d6d9e3bddf8@suse.
> com/

http://xenbits.xen.org/gitweb/?
p=xen.git;a=commit;h=c3bd0b83ea5b7c0da6542687436042eeea1e7909 is where it's 
committed in Xen's master branch. I haven't seen a backport to 4.16 (yet?)

Looking at the patch thread you linked, I get the impression that the change 
in the Linux kernel exposed the problem on the Xen side, but the Linux kernel 
change didn't introduce a bug (Andrew's patch seems to make it more 
informative, not correct a bug).

But I'm not sure that assesment is correct. What's your take on this?

Cheers,
  Diederik
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