Re: [PATCH v2 1/4] iommu/arm-smmu-v3: Add feature detection for HTTU

From: Jason Gunthorpe <jgg@nvidia.com>
To: Ryan Roberts <ryan.roberts@arm.com>
Cc: Shameer Kolothum <shameerali.kolothum.thodi@huawei.com>,
	iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	joro@8bytes.org, kevin.tian@intel.com, nicolinc@nvidia.com,
	mshavit@google.com, robin.murphy@arm.com, will@kernel.org,
	joao.m.martins@oracle.com, jiangkunkun@huawei.com,
	zhukeqian1@huawei.com, linuxarm@huawei.com
Subject: Re: [PATCH v2 1/4] iommu/arm-smmu-v3: Add feature detection for HTTU
Date: Wed, 24 Apr 2024 09:23:49 -0300	[thread overview]
Message-ID: <20240424122349.GH941030@nvidia.com> (raw)
In-Reply-To: <90985ae5-fa1c-40f5-b4b3-57350a16e011@arm.com>

On Wed, Apr 24, 2024 at 11:04:43AM +0100, Ryan Roberts wrote:
> On 23/04/2024 15:52, Jason Gunthorpe wrote:
> > On Tue, Apr 23, 2024 at 03:41:30PM +0100, Ryan Roberts wrote:
> >> Hi,
> >>
> >> I'm aiming to (slowly) get more involved with SMMU activities, although I'm sure
> >> it will take a while to get up to speed and provide useful input. It was
> >> suggested that this series would be a useful starting point to dip my toe in.
> >> Please bear with me while I ask stupid questions...
> > 
> > Nice!
> > 
> > I would like to see this merged as it was part of the original three
> > implementations for iommufd dirty tracking. The other two have been
> > merged for a long time now..
> 
> My understanding is that this series should pretty much apply on top of
> mainline, is that correct? (in practice there are some conflicts, but I think
> they are trivial).

It was originally based on my part 2, but I suspect it could apply
easially on top of part 2a. I don't think it is worth rebasing to
v6.9-rc since I expect Will to take 2a.

> I don't think it depends on anything new in your smmuv3_newapi branch?

I feel part 2a is done, hopefully Will will take it soon:

  https://lore.kernel.org/linux-iommu/0-v8-4c4298c63951+13484-smmuv3_newapi_p2_jgg@nvidia.com/

There are quite a few distros waiting on this:

  https://lore.kernel.org/linux-iommu/cover.1712977210.git.nicolinc@nvidia.com/

The cmdq area is not something I've studied deeply

I will be reposting the latter half of this as a part 2b:

  https://lore.kernel.org/linux-iommu/0-v6-228e7adf25eb+4155-smmuv3_newapi_p2_jgg@nvidia.com/

Which is the prerequisite for the part 3 series to enable nested
translation an vSMMUv3 for iommufd.

Nested translation and a few more bits is prerequisite to finally enable BTM:

  https://lore.kernel.org/linux-iommu/20240208151837.35068-1-shameerali.kolothum.thodi@huawei.com/

Thanks,
Jason

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