Re: [PATCH v2] x86/svm: Separate STI and VMRUN instructions in svm_asm_do_resume()

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 2/18/25 3:45 PM, Andrew Cooper wrote:

> On 18/02/2025 2:42 pm, Jan Beulich wrote:
> > On 18.02.2025 15:37, Andrew Cooper wrote:
> > > There is a corner case in the VMRUN instruction where its INTR_SHADOW state
> > > leaks into guest state if a VMExit occurs before the VMRUN is complete.  An
> > > example of this could be taking #NPF due to event injection.
> > >
> > > Xen can safely execute STI anywhere between CLGI and VMRUN, as CLGI blocks
> > > external interrupts too.  However, an exception (while fatal) will appear to
> > > be in an irqs-on region (as GIF isn't considered), so position the STI after
> > > the speculation actions but prior to the GPR pops.
> > >
> > > Link: https://lore.kernel.org/all/CADH9ctBs1YPmE4aCfGPNBwA10cA8RuAk2gO7542DjMZgs4uzJQ@xxxxxxxxxxxxxx/
> > > Fixes: 66b245d9eaeb ("SVM: limit GIF=0 region")
> > > Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > > Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> > > ---
> > > v2:
> > >  * Move after the speculation actions.
> > >
> > > Emailed out just for completeness.  I've queued it in my for-4.21 branch.
> > >         
> > It'll want backporting, so I wonder if we should persuade Oleksii into
> > taking it for 4.20.
> >       
>     
Based on that ...
> If Oleksii is happy, I can put it into 4.20.
... Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
Thanks.

~ Oleksii