Re: [Xen-devel] [Patch 2/4] Refining Xsave/Xrestore support

[Haitao Shan <maillists.shan@xxxxxxxxx>]

Thanks! I will update and send the patch out later.

Shan Haitao

2010/10/28 Keir Fraser <keir@xxxxxxx>:
> On 28/10/2010 08:52, "Haitao Shan" <maillists.shan@xxxxxxxxx> wrote:
>
>> Then I would prefer to write XCR0 unconditionally. Otherwise, I can
>> only refer to the approach for handling CR4 switches: reading CR4
>> first and checking whether there is a need to write actually.
>> But I don't think <a read to XCR0 plus a data comparison> can save any
>> compared with one unconditional write to XCR0.
>> Are you OK with this?
>
> Note that read_cr4() actually returns a cached copy of cr4, as stashed by
> write_cr4(). You should use the same trick for XCR0, and then do the
> cached-read-and-compare on context switch, again just as we do for cr4.
>
>  -- Keir
>
>> Thanks for pointing out the memory leak when hvm_vcpu_initialize
>> fails. I will update accordingly.
>>
>> Shan Haitao
>>
>> 2010/10/28 Jan Beulich <JBeulich@xxxxxxxxxx>:
>>>>>> On 28.10.10 at 06:58, Haitao Shan <maillists.shan@xxxxxxxxx> wrote:
>>>> This is the updated patch#2. Thanks.
>>>
>>> Sorry, but this is worse than not checking at all: You didn't consider
>>> the idle vCPU case here, and hence you may end up having more
>>> features enabled in xcr0 for a guest than it should have.
>>>
>>> Also I only now noticed that you're leaking the xsave_area allocation
>>> in vcpu_initialize() if hvm_vcpu_initialise() fails.
>>>
>>> Jan
>>>
>>>
>>
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>
>
>

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