Re: [Xen-devel] [PATCH v2 00/13] "Non-shared" IOMMU support on ARM

[Oleksandr Tyshchenko <olekstysh@xxxxxxxxx>]

СС persons from all patches in current series into the cover letter.

On Tue, Aug 1, 2017 at 9:09 PM, Julien Grall <julien.grall@xxxxxxx> wrote:
>
>
> On 01/08/17 04:06, Tian, Kevin wrote:
>>>
>>> From: Oleksandr Tyshchenko [mailto:olekstysh@xxxxxxxxx]
>>> Sent: Monday, July 31, 2017 7:58 PM
>>>
>>> Hi, Kevin
>>>
>>> On Mon, Jul 31, 2017 at 8:57 AM, Tian, Kevin <kevin.tian@xxxxxxxxx>
>>> wrote:
>>>>>
>>>>> From: Oleksandr Tyshchenko
>>>>> Sent: Wednesday, July 26, 2017 1:27 AM
>>>>>
>>>>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
>>>>>
>>>>> Hi, all.
>>>>>
>>>>> The purpose of this patch series is to create a base for porting
>>>>> any "Non-shared" IOMMUs to Xen on ARM. Saying "Non-shared" IOMMU
>>>
>>> I
>>>>>
>>>>> mean
>>>>> the IOMMU that can't share the page table with the CPU.
>>>>
>>>>
>>>> Is "non-shared" IOMMU a standard terminology in ARM side? I quickly
>>>> searched to find it mostly used in this thread...
>>>
>>> I don't think that it is a standard terminology.
>>>
>>>>
>>>> On the other hand, all IOMMUs support a basic DMA remapping
>>>> mechanism with page table not shared with CPU. Then some IOMMUs
>>>> may optional support Shared Virtual Memory (SVM) through page
>>>> sharing with CPU. Then I'm not sure why need to highlight the
>>>> "non-shared" manner in this thread, instead of just saying
>>>> IPMMU-VMSA support...
>>>
>>> I wouldn't use "IPMMU-VMSA support" in this thread since it may be any
>>> other IOMMUs which can't share page table
>>> with CPU because of format incompatibilities.
>>
>>
>> As I commented you can assume all IOMMUs cannot share page
>> table with CPU as the starting point. It's not good to name an IOMMU
>> driver based on such fact.
>
>
> As said in a previous reply. This is a wrong assumption, you can share
> page-tables with the IOMMU if the format is the same. You may still need to
> do TLB flush manually on the IOMMU, but you still save memory.
>
> x86 is already supporting that and also call "sharing" and is done by
> default (see iommu_hap_pt_share). If the naming is wrong, then feel free to
> send a patch.
>
> But I don't think you should complain about Oleksandr use this name.
>
> Cheers,
>
> --
> Julien Grall



-- 
Regards,

Oleksandr Tyshchenko

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel