Re: [Xen-devel] [PATCH 1/3] iommu: set correct IOMMU entries when iommu_hap_pt_share == 0

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On 08/04/14 10:30, Jan Beulich wrote:
>>>> On 07.04.14 at 18:02, <roger.pau@xxxxxxxxxx> wrote:
>> If the memory map is not shared between HAP and IOMMU we fails to set
>> correct IOMMU mappings for memory types different than p2m_ram_rw.
>>
>> This patchs adds IOMMU support for the following memory types:
>> p2m_grant_map_rw, p2m_map_foreign, p2m_ram_ro and p2m_grant_map_ro.
> 
> I'm curious about the justification for p2m_map_foreign; the others
> I agree with.

Thanks for the review, I didn't see a reason to not allow DMA transfers
to/from foreign pages, although there's no user of foreign pages that
use DMA.

> 
> I also wonder whether p2m_ram_logdirty shouldn't be treated
> equally to p2m_ram_rw: It's clearly better to have some video
> corruption than to kill the guest due to excessive IOMMU faults,
> should its kernel choose to DMA into the frame buffer. But at the
> very minimum this needs to be included alongside p2m_ram_ro.

Ack. I wasn't sure about p2m_ram_logdirty, so I just decided to not
include it. I will add it to my next revision as a RW zone if that's fine.

Roger.


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