linux-kernel - Re: [PATCH v8 5/7] iommu/arm-smmu-v3: Populate smmu

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Message-ID: <aUWfVzhVZ+Qo1efT@Asurada-Nvidia>
Date: Fri, 19 Dec 2025 10:54:15 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: Jason Gunthorpe <jgg@...dia.com>
CC: <will@...nel.org>, <jean-philippe@...aro.org>, <robin.murphy@....com>,
	<joro@...tes.org>, <balbirs@...dia.com>, <miko.lenczewski@....com>,
	<peterz@...radead.org>, <kevin.tian@...el.com>, <praan@...gle.com>,
	<linux-arm-kernel@...ts.infradead.org>, <iommu@...ts.linux.dev>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 5/7] iommu/arm-smmu-v3: Populate smmu_domain->invs
 when attaching masters

On Fri, Dec 19, 2025 at 11:51:51AM -0400, Jason Gunthorpe wrote:
> On Wed, Dec 17, 2025 at 03:24:30PM -0800, Nicolin Chen wrote:
> > +	*cur = inv;
> > +	switch (type) {
> > +	case INV_TYPE_S1_ASID:
> > +		if (master->smmu->features & ARM_SMMU_FEAT_E2H) {
> > +			cur->size_opcode = CMDQ_OP_TLBI_EL2_VA;
> > +			cur->nsize_opcode = CMDQ_OP_TLBI_EL2_ASID;
> > +		} else {
> > +			cur->size_opcode = CMDQ_OP_TLBI_NH_VA;
> > +			cur->nsize_opcode = CMDQ_OP_TLBI_NH_ASID;
> 
> There is a tricky little gotcha here that probably requires a comment.
> 
> NH_VA and NH_ASID both take (VMID,ASID) as input since the ASID is
> always scoped to a single VMID.
> 
> In this case the invalidation logic always wires the VMID to zero,
> which is also the VMID the driver uses for S1 tables when the S2 is in
> bypass.
> 
> Which is fine, we don't support an actual S1 table on top of a S2
> table where we issue invalidations through the invs array.
> 
> So maybe:
> 
>  For S1 page tables the driver always uses VMID=0, and the
>  invalidation logic for this type will set it as well.

Ack. And I will drop that ssid too.

Thanks
Nicolin