Re: [Xen-devel] question on share ept page table with vtd

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 01/02/2014 00:29, Zhang, Yang Z wrote:
> Hi all
>
> I have a question with the page table share between EPT and VTD which is 
> enabled by default. Currently, we will enable log_dirty mode to track vram. 
> And when first enable the log dirty mode, it will set all guest ram to 
> readonly in EPT entry. The question is that if a page is current used as DMA 
> write buffer, isn't it a problem?
>
> best regards
> yang

Looking at the code, it would indeed appear to be a problem.

Is has presumably gone unnoticed until now as all writes into the vram
would have been from software, and hit the log_dirty logic, rather than
DMA writes hitting the IOMMU.

~Andrew

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