Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit
From: Andy Lutomirski
Date: Tue Nov 17 2015 - 13:50:09 EST
On Nov 17, 2015 6:40 AM, "Boris Ostrovsky" <boris.ostrovsky@xxxxxxxxxx> wrote:
> On 11/16/2015 04:55 PM, H. Peter Anvin wrote:
>> On 11/16/15 12:22, Borislav Petkov wrote:
>>> Huh, so what's wrong with a jump:
>>> jmp 1f
>> What is the point of that jump?
>>>> If it would make you feel better, it could be X86_BUG_XENPV :-p
>>> That doesn't matter - I just don't want to open the flood gates on
>>> pseudo feature bits.
>>> hpa, what do you think?
>> Pseudo feature bits are fine, we already have plenty of them. They make
>> sense as they let us reuse a lot of infrastructure.
> So how about something like this? And then I think we can remove usergs_sysret32 and irq_enable_sysexit pv ops completely as noone will use them (lguest doesn't set them)
Looks good to me. Does Xen have any sysexit/sysret32 equivalent to
return to 32-bit user mode? If so, it could be worth trying to wire
it up by patching the jz instead of the test instruction.
Also, I'd prefer X86_FEATURE_XENPV. IMO "PV" means too many things to
too many people.
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