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From: Nicolin Chen <nicolinc@nvidia.com>
To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>,
	"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
	Linuxarm <linuxarm@huawei.com>,
	Zhangfei Gao <zhangfei.gao@linaro.org>,
	Michael Shavit <mshavit@google.com>,
	Eric Auger <eric.auger@redhat.com>,
	Moritz Fischer <mdf@kernel.org>,
	"baolu.lu@linux.intel.com" <baolu.lu@linux.intel.com>
Subject: Re: Query on ARM SMMUv3 nested support
Date: Fri, 29 Mar 2024 00:13:55 -0700	[thread overview]
Message-ID: <ZgZqMymQY4pL77iw@Asurada-Nvidia> (raw)
In-Reply-To: <4a37c695bf84425ea5159b82c202cb81@huawei.com>

Hi Shameer,

Sorry for the late reply. Having been occupied by multiple tasks
lately.

On Fri, Mar 22, 2024 at 03:04:42PM +0000, Shameerali Kolothum Thodi wrote:

> Thanks for the reference to above CMDQ-V. Looks interesting.
> I think we can have a go with retry logic first to allocate a new hwpt
> if the attach fails. For now, I have a temp fix where I allocate a new
> hwpt every time.
> 
> I also noticed another problem with the commit below,
> 6691a2f("hw/arm/smmu-common: Use sysmem for get_address _space until !!s2_hwpti")
> 
> This actually breaks a virtio-pci dev assignment when that is the only
> assigned device to the Guest without any pass-through dev in nested
> scenario.
>
> I have a temp fix for that as well here,
> (I know it is ugly!). I will revisit that again. Please let me know if you have
> any ideas.

I am not quite getting the case here. Is that virtio-pci device
behind a nested-SMMU while there is no S2 hwpt? In that case, why
does this virtio-pci device require a "nested-smmuv3"?

> I still have that io_uring write issue mentioned in the other thread[1],
> but for now I use io_uring API only for read and make use of normal write()
> for updating kernel with page response.
> 
> I have done some basic sanity runs with our ACC devices and those seems
> to work(of course needs more testing).
> 
> Please have a look and let me know if you spot anything.

I'm glad that you include the fault handling support. I'll give
that a try.

Thanks
Nicolin

next prev parent reply	other threads:[~2024-03-29  7:14 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-03-13 10:13 Query on ARM SMMUv3 nested support Shameerali Kolothum Thodi
2024-03-13 23:50 ` Nicolin Chen
2024-03-18 16:22   ` Jason Gunthorpe
2024-03-22 15:04   ` Shameerali Kolothum Thodi
2024-03-29  7:13     ` Nicolin Chen [this message]
2024-04-02  7:25       ` Shameerali Kolothum Thodi
2024-04-02 11:28         ` Jason Gunthorpe
2024-04-09  6:12         ` Nicolin Chen
2024-04-09 19:47           ` Nicolin Chen

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