linux-kernel - Re: [RFC PATCH v1 2/8] iommu/arm-smmu-v3: Perform invalidations over installed

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Message-ID: <ZN93TO9mRIrX1grw@nvidia.com>
Date:   Fri, 18 Aug 2023 10:51:08 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Michael Shavit <mshavit@...gle.com>
Cc:     Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        will@...nel.org, nicolinc@...dia.com, tina.zhang@...el.com,
        jean-philippe@...aro.org
Subject: Re: [RFC PATCH v1 2/8] iommu/arm-smmu-v3: Perform invalidations over
 installed_smmus

On Fri, Aug 18, 2023 at 11:44:55AM +0800, Michael Shavit wrote:
> On Fri, Aug 18, 2023 at 3:41 AM Robin Murphy <robin.murphy@....com> wrote:
> >
> > On 2023-08-17 20:20, Jason Gunthorpe wrote:
> > > It is certainly wrong to skip invalidations generated for any other
> > > reason.
> > >
> > >  From what I can tell SVA domains should have their CD table entry
> > > programmed with "ASET=0" and normal paging domains should be
> > > programmed with "ASET=1". This causes only the SVA domains to listen
> > > to the BTM invalidations.
> >
> > Correct.
> >
> > Thanks,
> > Robin.
> 
> Would it be fair to rename arm_smmu_tlb_inv_asid (or move into
> arm-smmu-v3-sva) to make it explicit that it shouldn't be used outside
> of SVA then? Or add a parameter such as skip_btm_capable_devices.

???

arm_smmu_tlb_inv_asid() is generally used in many places and has
nothing to do with BTM..

Did you mean arm_smmu_tlb_inv_range_asid ?

Broadly, invalidation is not SVA specific..

Notice that arm_smmu_tlb_inv_range_asid() already duplicates
arm_smmu_tlb_inv_range_domain().

IMHO I would split the ATC step out of arm_smmu_mm_invalidate_range(),
get rid of arm_smmu_tlb_inv_range_domain(), and have the mmu notifier
just do as it already does:

	if (!(smmu_domain->smmu->features & ARM_SMMU_FEAT_BTM))
		arm_smmu_tlb_inv_range_domain_no_atc(start, size, smmu_mn->cd->asid,
					    PAGE_SIZE, false, smmu_domain);
	arm_smmu_atc_inv_domain(smmu_domain, start, size);

And make arm_smmu_tlb_inv_range_domain() just call
   arm_smmu_tlb_inv_range_domain_no_atc();
   arm_smmu_atc_inv_domain();

Jason