On 27/04/17 00:04, Borislav Petkov wrote:
> On Wed, Apr 26, 2017 at 08:24:12PM +0200, Juergen Gross wrote:
>> I'm not feeling strong about it. So if you want to test for
>> X86_FEATURE_XENPV to avoid setting X86_BUG_SYSRET_SS_ATTRS I'm fine
>> with it.
>>
>> Will send V2 with that change.
>
> And
On Wed, Apr 26, 2017 at 08:24:12PM +0200, Juergen Gross wrote:
> I'm not feeling strong about it. So if you want to test for
> X86_FEATURE_XENPV to avoid setting X86_BUG_SYSRET_SS_ATTRS I'm fine
> with it.
>
> Will send V2 with that change.
And remove the corresponding
clear_cpu_bug(c, X
On 26/04/17 08:35, Borislav Petkov wrote:
> On Wed, Apr 26, 2017 at 06:45:42AM +0200, Juergen Gross wrote:
>> The really clean solution would be to add this test to set_cpu_bug()
>
> No, the really clean solution is to set it once and not play toggle
> games.
>
>> This would work. OTOH I'd prefer
On Wed, Apr 26, 2017 at 06:45:42AM +0200, Juergen Gross wrote:
> The really clean solution would be to add this test to set_cpu_bug()
No, the really clean solution is to set it once and not play toggle
games.
> This would work. OTOH I'd prefer to test whether the bit should be
> forced to remain
On 25/04/17 21:18, Borislav Petkov wrote:
> On Tue, Apr 25, 2017 at 08:34:34PM +0200, Juergen Gross wrote:
>> And what happens when there is a scheduling event right here?
>> __switch_to() will see X86_BUG_SYSRET_SS_ATTRS set and take a wrong
>> path.
>
> So the whole thing we're doing right now i
On Tue, Apr 25, 2017 at 09:17:13PM +0100, Andrew Cooper wrote:
> The problem (for all ring-deprivileged virtuailsation; not just Xen PV),
> is that
I know what that that bug flag is for.
I'm asking whether the xen guest boot sets a flag early - like XENPV,
for example - which can differentiate be
On 25/04/17 20:18, Borislav Petkov wrote:
> On Tue, Apr 25, 2017 at 08:34:34PM +0200, Juergen Gross wrote:
>> And what happens when there is a scheduling event right here?
>> __switch_to() will see X86_BUG_SYSRET_SS_ATTRS set and take a wrong
>> path.
> So the whole thing we're doing right now is w
On Tue, Apr 25, 2017 at 08:34:34PM +0200, Juergen Gross wrote:
> And what happens when there is a scheduling event right here?
> __switch_to() will see X86_BUG_SYSRET_SS_ATTRS set and take a wrong
> path.
So the whole thing we're doing right now is wrong: set bit and then
clear bit.
We should not
On 25/04/17 20:24, Borislav Petkov wrote:
> On Tue, Apr 25, 2017 at 08:00:14PM +0200, Juergen Gross wrote:
>> When running as Xen pv guest X86_BUG_SYSRET_SS_ATTRS must not be set
>> on AMD cpus. Xen will disable this via setup_clear_cpu_cap(), so test
>> cpu_caps_cleared to not have disabled this b
On Tue, Apr 25, 2017 at 08:00:14PM +0200, Juergen Gross wrote:
> When running as Xen pv guest X86_BUG_SYSRET_SS_ATTRS must not be set
> on AMD cpus. Xen will disable this via setup_clear_cpu_cap(), so test
> cpu_caps_cleared to not have disabled this bit.
>
> This bug/feature bit is kind of specia
When running as Xen pv guest X86_BUG_SYSRET_SS_ATTRS must not be set
on AMD cpus. Xen will disable this via setup_clear_cpu_cap(), so test
cpu_caps_cleared to not have disabled this bit.
This bug/feature bit is kind of special as it will be used very early
when switching threads. Setting the bit a
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