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

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


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.


Julien Grall



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