Re: [RFC PATCH v1 3/8] iommu/arm-smmu-v3-sva: Allocate new ASID from installed_smmus

From: Jason Gunthorpe <jgg@nvidia.com>
To: Michael Shavit <mshavit@google.com>
Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, will@kernel.org,
	nicolinc@nvidia.com, tina.zhang@intel.com,
	jean-philippe@linaro.org, robin.murphy@arm.com
Subject: Re: [RFC PATCH v1 3/8] iommu/arm-smmu-v3-sva: Allocate new ASID from installed_smmus
Date: Mon, 21 Aug 2023 11:56:14 -0300	[thread overview]
Message-ID: <ZON7Dt4Hkf8iwaDC@nvidia.com> (raw)
In-Reply-To: <CAKHBV25P9kNGkM7f5Xc-HsozK362XzMz+NnLa8FcWiu3FFr13g@mail.gmail.com>

On Mon, Aug 21, 2023 at 10:39:14PM +0800, Michael Shavit wrote:
> > > > > (on a loop over every smmu the domain in arm_smmu_mmu_notifier_get is
> > > > > attached to, which just at a glance looks headache inducing because of
> > > > > sva's piggybacking on the rid domain.)
> > > >
> > > > Not every smmu, just the one you are *currently* attaching to. We
> > > > don't care if the *other* smmu's have different ASIDs, maybe they are
> > > > not using BTM, or won't use SVA.
> > >
> > > I mean because the domain in arm_smmu_mmu_notifier_get is the RID
> > > domain (not the SVA domain, same issue we discussed in previous
> > > thread) , which can be attached to multiple SMMUs.
> >
> > Oh that is totally nonsensical. I expect you will need to fix that
> > sooner than later. Once the CD table is moved and there is a proper
> > way to track the PASID it should not be needed. It shouldn't fall into
> > the decision making about where to put the ASID xarray.
> 
> Right I got a bit of a chicken and egg problem with all these series.

Yes, I'm not surprised to hear this

Still, it would nice to move forward without going in a weird
direction too much.

Once the CD table is moved to the master what do you think is blocking
fixing up the SVA stuff to not rely on a RID domain?

Jason