Re: [Xen-devel] [PATCH 4/5] x86/PV: remove the emulated PIT

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 14.01.16 at 09:25, <roger.pau@xxxxxxxxxx> wrote:
> El 13/01/16 a les 17.36, Jan Beulich ha escrit:
>>>>> On 13.01.16 at 13:32, <roger.pau@xxxxxxxxxx> wrote:
>>> The HVMlite series removed the initialization of the emulated PIT for PV
>>> guests, but the handler was still reachable, which means a PV guests can
>>> crash Xen if it pokes at IO ports 0x42, 0x43 or 0x61. Completely remove the
>>> PV PIT handler and move the PIT initialization to HVM guests only.
>> 
>> As said on IRC - this is needed for Dom0 to be able to drive the
>> PC speaker. You'll need to provide a fix for the suppressed
>> initialization instead, at least for Dom0. (As an aside, your patch
>> orphans hwdom_pit_access().)
> 
> Thanks for the clarification. AFAICT I can leave the usage of
> hwdom_pit_access for Dom0, and completely remove PIT access for DomU, is
> that right?

I don't think so - see the explanation Tim gave on IRC. Afaict the
mention of BIOS here isn't related to a virtual BIOS, but to that
of a passed through graphics card.

Jan


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