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 16:12, Tim Deegan wrote:
> At 09:30 +0100 on 08 Apr (1396945844), 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 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,
> 
> Hmmm.  In that case it seems better; if we're absolutely sure that we
> can't end up trying to do log-dirty for _migration_ while a guest has
> a real device passed through, then yes, we can leave them as r/w to
> the IOMMU. 
> 
> Maybe make sure at the same time that full log-dirty mode and
> needs_iommu are mutually exclusive.

Would it suffice to add something like:

case p2m_ram_logdirty:
    ASSERT(!paging_mode_log_dirty(p2m->domain));

Or are you referring to a more global check?

Thanks, Roger.


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