[Xen-devel] Re: XEN monitor/mwait patch for AMD SVM

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

That's firmly in the 'Doctor, it hurts when I...' category I'm afraid. No
way will I apply this type of patch.

 -- Keir

On 22/05/2009 18:10, "Boppuri, Navin" <Navin.Boppuri@xxxxxxx> wrote:

> Keir,
> 
> Sorry but the patch is against the latest tip of the xen unstable tree
> (changeset: 18646).
> 
> I understand that MWAIT is not mentioned in the whitelist for HVM policy.
> However, one could modify the guest config file and set the cpuid bit for
> monitor/mwait and enable this feature by force. I was able to do just this in
> my test configuration. This patch should cover such mods for cpuid in addition
> to the cpuid policy in libxc.
> 
> Thank you.
> -Navin
> 
>> -----Original Message-----
>> From: Keir Fraser [mailto:keir.fraser@xxxxxxxxxxxxx]
>> Sent: Friday, May 22, 2009 11:40 AM
>> To: Boppuri, Navin; xen-devel@xxxxxxxxxxxxxxxxxxx
>> Subject: Re: XEN monitor/mwait patch for AMD SVM
>> 
>> On 22/05/2009 16:23, "Boppuri, Navin" <Navin.Boppuri@xxxxxxx> wrote:
>> 
>>> This patch clears the monitor/mwait bit in the cpuid intercept code for
>> AMD¹s
>>> SVM. This is to disallow VM¹s that may try and use the monitor/mwait
>> feature
>>> on AMD processors which is currently not supported in XEN.
>>> 
>>> Signed-off-by: Navin Boppuri <navin.boppuri@xxxxxxx>
>> 
>> What Xen version is this patch against? We already hide MWAIT from HVM
>> guests as far as I am aware. See
>> tools/libxc/xc_cpuid_x86.c:xc_cpuid_hvm_policy(), and note that features
>> are
>> *whitelisted* and also that MWAIT is *not* mentioned.
>> 
>> So I think your patch is not needed, and also inappropriate since we
>> implement CPUID filtering policy in libxc these days.
>> 
>>  -- Keir
>> 
>> 
> 
> 



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