Re: [Xen-devel] [PATCH] x86/mm: disallow mmu hypercalls for a dying domain

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

Probably coming from dom0 userspace somewhere, such as qemu. By the time you
get down to the hypercall implementation in Xen, you've already done the
expensive traps via dom0 kernel.

 -- Keir

On 27/11/2009 09:10, "Kouya Shimura" <kouya@xxxxxxxxxxxxxx> wrote:

> I observed that dom0 kept on issuing a mmu_update hypercall while the
> domain is dying. So I don't feel happy with it.
> But I'm ok if the patch is dropped.
> 
> Thanks,
> Kouya
> 
> Keir Fraser writes:
>> Since the check is made with no locks held, I don't think any race can be
>> completely avoided here. I'm not sure the performance argument holds much
>> water either -- this just looks like a pointless extra check.
>> 
>>  -- Keir
>> 
>> On 27/11/2009 06:22, "Kouya Shimura" <kouya@xxxxxxxxxxxxxx> wrote:
>> 
>>> The race condition should be avoided for efficiency.
>>> 
>>> Signed-off-by: Kouya Shimura <kouya@xxxxxxxxxxxxxx>
>>> 
>> 



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