This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


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

To: Kouya Shimura <kouya@xxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] x86/mm: disallow mmu hypercalls for a dying domain
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Fri, 27 Nov 2009 09:43:54 +0000
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Fri, 27 Nov 2009 01:44:15 -0800
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <7kljhsxrik.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcpvQW+CikZ+PqhbQ7G/eCAzI1LWyAABLJZH
Thread-topic: [Xen-devel] [PATCH] x86/mm: disallow mmu hypercalls for a dying domain
User-agent: Microsoft-Entourage/
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>

Xen-devel mailing list

<Prev in Thread] Current Thread [Next in Thread>