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Re: [Xen-devel] [PATCH 1/5] Add MSI support to XEN

To: "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx>, "Shan, Haitao" <haitao.shan@xxxxxxxxx>, Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH 1/5] Add MSI support to XEN
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Fri, 28 Mar 2008 09:45:27 +0000
Cc: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "Li, Xin B" <xin.b.li@xxxxxxxxx>
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On 28/3/08 09:37, "Jiang, Yunhong" <yunhong.jiang@xxxxxxxxx> wrote:

> DomainU  (PV and hvm) should have no idea of vector. Do you think it
> will matter if domain0 have such idea?
> one thing missed here is, if domainU want to access the MSI config
> spafce, pci backend should return 0xff. Then it should be secure if
> domain0 can have idea of vector.

No, it's not a security risk for dom0 kernel to know about real vectors.
It's already part of the TCB.

It's just a question of which is the cleanest design. And letting Xen get
some access to PCI config space (just a little -- not a lot -- and under
direction of dom0 kernel) will let it properly mask MSIs, which would be a
nicer and deadlock-free alternative to the 'ACK-NEW' masking method.

 -- Keir



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