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Re: [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests

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  Re: [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-12-15 16:30 +0100
    Re: [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests Borislav Petkov <bp@suse.de> - 2015-12-15 16:50 +0100
      Re: [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests Andy Lutomirski <luto@amacapital.net> - 2015-12-15 17:00 +0100
      Re: [PATCH v2 1/3] x86/xen: Avoid fast syscall path for Xen PV guests Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-12-15 17:10 +0100

#1292255 — Re: [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@oracle.com>
> Suggested-by: Andy Lutomirski <luto@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

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#1292296

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?

Thanks.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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#1292310

On Tue, Dec 15, 2015 at 7:54 AM, Boris Ostrovsky
<boris.ostrovsky@oracle.com> wrote:
> 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.

Agreed.

>
> Thanks.
> -boris
>
>
>



-- 
Andy Lutomirski
AMA Capital Management, LLC
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#1292315

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



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