Re: [XEN PATCH v1] xen/arm : Add support for SMMUv3 driver

[Oleksandr Andrushchenko <Oleksandr_Andrushchenko@xxxxxxxx>]

Hi,

On 11/2/20 11:55 AM, Bertrand Marquis wrote:
> Hi,
>
>> On 2 Nov 2020, at 05:55, Oleksandr Andrushchenko <andr2000@xxxxxxxxx> wrote:
>>
>> Hi, Julien!
>>
>> On 10/30/20 7:18 PM, Julien Grall wrote:
>>> Hi Oleksandr,
>>>
>>> On 30/10/2020 10:44, Oleksandr Andrushchenko wrote:
>>>> On 10/20/20 6:25 PM, Rahul Singh wrote:
>>>>> Add support for ARM architected SMMUv3 implementations. It is based on
>>>>> the Linux SMMUv3 driver.
>>>>>
>>>>> Major differences between the Linux driver are as follows:
>>>>> 1. Only Stage-2 translation is supported as compared to the Linux driver
>>>>>       that supports both Stage-1 and Stage-2 translations.
>>>> First of all thank you for the efforts!
>>>>
>>>> I tried the patch with QEMU and would like to know if my understanding 
>>>> correct
>>>>
>>>> that this combination will not work as of now:
>>>>
>>>> (XEN) SMMUv3: /smmuv3@9050000: SMMUv3: DT value = eventq
>>>> (XEN) Data Abort Trap. Syndrome=0x1940010
>>>> (XEN) Walking Hypervisor VA 0x40031000 on CPU0 via TTBR 0x00000000b8469000
>>>> (XEN) 0TH[0x0] = 0x00000000b8468f7f
>>>>
>>>> [snip]
>>>>
>>>> If this is expected then is there any plan to make QEMU work as well?
>>>>
>>>> I see [1] says that "Only stage 1 and AArch64 PTW are supported." on QEMU 
>>>> side.
>>> Just for clarication, you are trying to boot Xen on QEMU, right?
>> Exactly
>>> You might be able to use the stage-1 page-tables to isolate each device in 
>>> Xen. However, I don't think you will be able to share the P2M because the 
>>> page-tables layout between stage-1 and stage-2 is different.
>> So, it is even more work then
> Overall it would make more sense to spend some time adding proper support in 
> Qemu then trying to modify the driver to support Qemu right now.
>
>>>>
>>>> We are interested in QEMU/SMMUv3 as a flexible platform for PCI passthrough
>>>>
>>>> implementation, so it could allow testing different setups and 
>>>> configurations with QEMU.
>>> I would recommend to get the SMMU supporting supporting stage-2 page-tables.
>> You mean in QEMU?
> See before.
>
>>> Regardless that, I think Xen should be able to say the SMMU is not 
>>> supported rather than crashing.
>> Yes, that would be nice
> Fully agree and we will look into that.
>
> Anything you could share so that we could quickly reproduce your setup would 
> be more then great.

Nothing special,

qemu/aarch64-softmmu/qemu-system-aarch64 -machine type=virt -machine 
virt,gic-version=2 \

-machine virtualization=true -cpu cortex-a57 -smp 4 -m 2048 -nic 
user,hostfwd=tcp:127.0.0.1:2222-:22 \

-nographic -serial mon:stdio [..snip..]

I also set iommu to smmuv3 in my tests, QEMU emulator version 4.2.1

>
> Regards
> Bertrand
>
>>> Cheers,
>>>
>> Thank you,
>>
>> Oleksandr