Messages in this thread | | | From | Andy Lutomirski <> | Date | Tue, 17 Nov 2015 10:49:40 -0800 | Subject | Re: [PATCH] xen/x86: Adjust stack pointer in xen_sysexit |
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On Nov 17, 2015 6:40 AM, "Boris Ostrovsky" <boris.ostrovsky@oracle.com> 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 >>> swapgs >>> 1: >>> >> 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.
--Andy
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