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.

I've spoken with Stefano about this, because I've seen Qemu use foreign
mapped pages as arguments to systems calls like pread/pwrite, and I'm
quite sure we need IOMMU entries for foreign mappings. If Qemu opens the
disk file with O_DIRECT foreign mappings can end up in DMA requests.

Roger.


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