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

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

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
> > 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?
> Regardless that, I think Xen should be able to say the SMMU is not supported 
> rather than crashing.
Yes, that would be nice
> Cheers,
Thank you,

Oleksandr