linux-kernel - Re: [PATCH v5 13/14] iommu/arm-smmu-v3: Introduce struct arm_smmu

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Message-ID: <Z4VvGIYtbCOj53qf@Asurada-Nvidia>
Date: Mon, 13 Jan 2025 11:52:56 -0800
From: Nicolin Chen <nicolinc@...dia.com>
To: Jason Gunthorpe <jgg@...dia.com>
CC: <kevin.tian@...el.com>, <corbet@....net>, <will@...nel.org>,
	<joro@...tes.org>, <suravee.suthikulpanit@....com>, <robin.murphy@....com>,
	<dwmw2@...radead.org>, <baolu.lu@...ux.intel.com>, <shuah@...nel.org>,
	<linux-kernel@...r.kernel.org>, <iommu@...ts.linux.dev>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kselftest@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <eric.auger@...hat.com>,
	<jean-philippe@...aro.org>, <mdf@...nel.org>, <mshavit@...gle.com>,
	<shameerali.kolothum.thodi@...wei.com>, <smostafa@...gle.com>,
	<ddutile@...hat.com>, <yi.l.liu@...el.com>, <patches@...ts.linux.dev>
Subject: Re: [PATCH v5 13/14] iommu/arm-smmu-v3: Introduce struct
 arm_smmu_vmaster

On Mon, Jan 13, 2025 at 03:29:27PM -0400, Jason Gunthorpe wrote:
> On Tue, Jan 07, 2025 at 09:10:16AM -0800, Nicolin Chen wrote:
> 
> > +int arm_smmu_attach_prepare_vmaster(struct arm_smmu_attach_state *state,
> > +				    struct iommu_domain *domain)
> > +{
> > +	struct arm_smmu_nested_domain *nested_domain;
> > +	struct arm_smmu_vmaster *vmaster;
> > +	unsigned long vsid;
> > +	unsigned int cfg;
> > +
> > +	iommu_group_mutex_assert(state->master->dev);
> > +
> > +	if (domain->type != IOMMU_DOMAIN_NESTED)
> > +		return 0;
> > +	nested_domain = to_smmu_nested_domain(domain);
> > +
> > +	/* Skip ABORT/BYPASS or invalid vSTE */
> > +	cfg = FIELD_GET(STRTAB_STE_0_CFG, le64_to_cpu(nested_domain->ste[0]));
> > +	if (cfg == STRTAB_STE_0_CFG_ABORT || cfg == STRTAB_STE_0_CFG_BYPASS)
> > +		return 0;
> 
> Why? If the VM sets an ABORT vSTE then I would expect that any
> protection violation events the VM triggers are captured and forwarded
> as well?
>
> Basically any time a vSTE is in place we should capture events that
> are affiliated with the SID?

I see. I will drop this.
 
> > +	if (!(nested_domain->ste[0] & cpu_to_le64(STRTAB_STE_0_V)))
> > +		return 0;
> > +
> > +	vsid = iommufd_viommu_get_vdev_id(&nested_domain->vsmmu->core,
> > +					  state->master->dev);
> > +	/* Fail the attach if vSID is not correct set by the user space */
> > +	if (!vsid)
> > +		return -ENOENT;
> 
> Is it really OK that 0 is being used as invalid here?

Hmm, perhaps better to do an int function for -ENOENT. Will fix
this.

Thanks
Nicolin