lkml.org 
[lkml]   [2014]   [Jan]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v12 03/18] xen/pvh: Early bootup changes in PV code (v2).
On 03/01/14 01:34, Mukesh Rathor wrote:
> On Thu, 2 Jan 2014 13:32:21 -0500
> Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> wrote:
>
>> On Thu, Jan 02, 2014 at 03:32:33PM +0000, David Vrabel wrote:
>>> On 01/01/14 04:35, Konrad Rzeszutek Wilk wrote:
>>>> From: Mukesh Rathor <mukesh.rathor@oracle.com>
>>>>
>>>> In the bootup code for PVH we can trap cpuid via vmexit, so don't
>>>> need to use emulated prefix call. We also check for vector
>>>> callback early on, as it is a required feature. PVH also runs at
>>>> default kernel IOPL.
>>>>
>>>> Finally, pure PV settings are moved to a separate function that
>>>> are only called for pure PV, ie, pv with pvmmu. They are also
>>>> #ifdef with CONFIG_XEN_PVMMU.
>>> [...]
>>>> @@ -331,12 +333,15 @@ static void xen_cpuid(unsigned int *ax,
>>>> unsigned int *bx, break;
>>>> }
>>>>
>>>> - asm(XEN_EMULATE_PREFIX "cpuid"
>>>> - : "=a" (*ax),
>>>> - "=b" (*bx),
>>>> - "=c" (*cx),
>>>> - "=d" (*dx)
>>>> - : "0" (*ax), "2" (*cx));
>>>> + if (xen_pvh_domain())
>>>> + native_cpuid(ax, bx, cx, dx);
>>>> + else
>>>> + asm(XEN_EMULATE_PREFIX "cpuid"
>>>> + : "=a" (*ax),
>>>> + "=b" (*bx),
>>>> + "=c" (*cx),
>>>> + "=d" (*dx)
>>>> + : "0" (*ax), "2" (*cx));
>>>
>>> For this one off cpuid call it seems preferrable to me to use the
>>> emulate prefix rather than diverge from PV.
>>
>> This was before the PV cpuid was deemed OK to be used on PVH.
>> Will rip this out to use the same version.
>
> Whats wrong with using native cpuid? That is one of the benefits that
> cpuid can be trapped via vmexit, and also there is talk of making PV
> cpuid trap obsolete in the future. I suggest leaving it native.

It should either use the PV interface or the HVM one, not a hybrid of
the two.

David


\
 
 \ /
  Last update: 2014-01-03 13:01    [W:0.113 / U:0.188 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site