RE: [Xen-ia64-devel] VTD is coming

[Akio Takebe <takebe_akio@xxxxxxxxxxxxxx>]

Hi, Anthony

Thank you for your explanation.

>>I have a question.
>>Do we need to set not only tables included dma page
>>but also all page table to VTd?
>We don't know which pages guest OS will use as dma page,
>So we let vtd page table translate all physical address 
>belonging to guest.
>
>>If yes, do we need to diable dma even when we chage any page table
>>not related in dma-remapping?
>
>we needn't and can't.
>Vtd page table is maintained by xen.
>When xen changes vtd page table, the changed entries should not
>be used by DMA operation. What xen needs to do is to flush corresponding IO-
>TLBs.
>
Thanks, I understand.

Another question, xen don't know dma pages used by guest,
how about can xen protect the dma pages?
(Sorry, I'll read VTd spec much more.)

>Do you find the scenarios where race conditions exist?
>
No, I was warried about performance at the time of changing page table.

Best Regards,

Akio Takebe


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