From: Keir Fraser <keir.fraser@eu.citrix.com>
To: Kouya Shimura <kouya@jp.fujitsu.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
Subject: Re: [PATCH] x86/mm: disallow mmu hypercalls for a dying domain
Date: Fri, 27 Nov 2009 09:43:54 +0000 [thread overview]
Message-ID: <C7354FDA.2E49%keir.fraser@eu.citrix.com> (raw)
In-Reply-To: <7kljhsxrik.fsf@pingu.sky.yk.fujitsu.co.jp>
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@jp.fujitsu.com> 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@jp.fujitsu.com> wrote:
>>
>>> The race condition should be avoided for efficiency.
>>>
>>> Signed-off-by: Kouya Shimura <kouya@jp.fujitsu.com>
>>>
>>
prev parent reply other threads:[~2009-11-27 9:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-11-27 6:22 [PATCH] x86/mm: disallow mmu hypercalls for a dying domain Kouya Shimura
2009-11-27 8:08 ` Keir Fraser
2009-11-27 9:10 ` Kouya Shimura
2009-11-27 9:43 ` Keir Fraser [this message]
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