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Re: [Xen-devel] [PATCH v1 0/2] Extend ioreq-server to support page write protection
- To: "Kevin Tian" <kevin.tian@xxxxxxxxx>
- From: "Jan Beulich" <JBeulich@xxxxxxxx>
- Date: Fri, 15 Aug 2014 00:12:12 +0100
- Cc: "keir@xxxxxxx" <keir@xxxxxxx>, "ian.campbell@xxxxxxxxxx" <ian.campbell@xxxxxxxxxx>, "stefano.stabellini@xxxxxxxxxxxxx" <stefano.stabellini@xxxxxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, "ian.jackson@xxxxxxxxxxxxx" <ian.jackson@xxxxxxxxxxxxx>, Donald D Dugger <donald.d.dugger@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxx>, "Paul.Durrant@xxxxxxxxxx" <Paul.Durrant@xxxxxxxxxx>, Zhiyuan Lv <zhiyuan.lv@xxxxxxxxx>, Yang Z Zhang <yang.z.zhang@xxxxxxxxx>, Wei Ye <wei.ye@xxxxxxxxx>
- Delivery-date: Thu, 14 Aug 2014 23:12:17 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
>>> On 15.08.14 at 00:53, <kevin.tian@xxxxxxxxx> wrote:
> btw just curious how we handle p2m_ram_ro today. Does it play any trick
> to fail-safe in IOMMU side, e.g. zap the mapping or not? Otherwise when
> it allows read-only DMA there's no way to prevent DMA writes either. :-)
Why would that be? A page marked r/o in the IOMMU page tables
ought to very well be protected against DMA writes. It's just that
these will cause faults, which - if happening too frequently - will
result in the device getting turned off, quite likely (implicitly) killing
the guest.
Jan
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