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

[Julien Grall <julien@xxxxxxx>]

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?

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.
> 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.

Regardless that, I think Xen should be able to say the SMMU is not 
supported rather than crashing.
Cheers,

--
Julien Grall