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Re: [Xen-devel] [PATCH v1 0/2] Extend ioreq-server to support page write protection

>>> 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.


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