Virtualization - Dec 2015 - [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests

On 11/19/2015 04:55 PM, Boris Ostrovsky wrote:
> After 32-bit syscall rewrite, and specifically after commit 5f310f739b4c
> ("x86/entry/32: Re-implement SYSENTER using the new C path"), the
stack
> frame that is passed to xen_sysexit is no longer a "standard" one
(i.e.
> it's not pt_regs).
>
> Since we end up calling xen_iret from xen_sysexit we don't need to fix
> up the stack and instead follow entry_SYSENTER_32's IRET path directly
> to xen_iret.
>
> We can do the same thing for compat mode even though stack does not need
> to be fixed. This will allow us to drop usergs_sysret32 paravirt op (in
> the subsequent patch)
>
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky at oracle.com>
> Suggested-by: Andy Lutomirski <luto at amacapital.net>

I know this has been in the tip tree --- when do you think this will go 
Linus tree? In the 4.4 timeframe?

Xen 32-bit PV guests are broken without this.


Thanks.
-boris

On 12/15/2015 10:48 AM, Borislav Petkov wrote:
> On Tue, Dec 15, 2015 at 10:21:37AM -0500, Boris Ostrovsky wrote:
>> I know this has been in the tip tree --- when do you think this will go
>> Linus tree? In the 4.4 timeframe?
> It is queued for 4.5 currently.
>
>> Xen 32-bit PV guests are broken without this.
> So this needs to go into 4.4 or even earlier? Since 5f310f739b4c went
> into 4.4, I'd think 4.4 only for this fix too? Yes?
Oh, I didn't realize this is scheduled for 4.5. It indeed needs to go 
into 4.4 because of 5f310f739b4c.

Thanks.
-boris