Re: [Xen-devel] Failed vm entry with heavy use of emulator

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

On Tue, Jan 5, 2016 at 3:01 PM, Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> wrote:

On 01/05/2016 03:49 PM, Andrew Cooper wrote:
> On 05/01/16 13:39, Razvan Cojocaru wrote:
>> Here's a quick log of the emulated instructions on my setup:
>> http://pastebin.com/raw/XXQ0Lnzh
>
> Hmm - according to that, the final instruction emulated was
>
> d1v0 32bit @ 0008:828925db -> fa
>
> which is the 'cli' instruction.
>
> I would start there - I doubt it is an instruction which is emulated often.

My code (arch/x86/x86_emulate/x86_emulate.c) does have a case label for it:

3677Â Â Âcase 0xfa: /* cli */
3678Â Â Â Â Âgenerate_exception_if(!mode_iopl(), EXC_GP, 0);
3679Â Â Â Â Â_regs.eflags &= ~EFLG_IF;
3680Â Â Â Â Âbreak;

Maybe the IOPL test fails there? Tamas, does your guest die after a CLI
as well?

I've added a gdprintk(XENLOG_DEBUG, "emulate 0xfa cli\n"); into that switch case but it wasn't printed before the guest crashed.

Tamas

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