linux-kernel - Re: [PATCH v7 12/14] iommu/arm-smmu-v3: Introduce struct arm_smmu

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Message-ID: <Z73zvIbsXzJMCaNt@google.com>
Date: Tue, 25 Feb 2025 16:45:48 +0000
From: Pranjal Shrivastava <praan@...gle.com>
To: Jason Gunthorpe <jgg@...dia.com>
Cc: Nicolin Chen <nicolinc@...dia.com>, 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 v7 12/14] iommu/arm-smmu-v3: Introduce struct
 arm_smmu_vmaster

On Tue, Feb 25, 2025 at 12:02:25PM -0400, Jason Gunthorpe wrote:
> On Mon, Feb 24, 2025 at 03:45:33PM -0800, Nicolin Chen wrote:
> 
> > --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
> > +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3-iommufd.c
> > @@ -95,8 +95,6 @@ int arm_smmu_attach_prepare_vmaster(struct arm_smmu_attach_state *state,
> >  
> >  	iommu_group_mutex_assert(state->master->dev);
> >  
> > -	if (domain->type != IOMMU_DOMAIN_NESTED)
> > -		return 0;
> >  	nested_domain = to_smmu_nested_domain(domain);
> >  
> >  	/* Skip invalid vSTE */
> > @@ -122,19 +120,9 @@ void arm_smmu_attach_commit_vmaster(struct arm_smmu_attach_state *state)
> >  {
> >  	struct arm_smmu_master *master = state->master;
> >  
> > -	mutex_lock(&master->smmu->streams_mutex);
> > -	if (state->vmaster != master->vmaster) {
> > -		kfree(master->vmaster);
> > -		master->vmaster = state->vmaster;
> > -	}
> > -	mutex_unlock(&master->smmu->streams_mutex);
> > -}
> > -
> > -void arm_smmu_master_clear_vmaster(struct arm_smmu_master *master)
> > -{
> >  	mutex_lock(&master->smmu->streams_mutex);
> >  	kfree(master->vmaster);
> > -	master->vmaster = NULL;
> > +	master->vmaster = state->vmaster;
> >  	mutex_unlock(&master->smmu->streams_mutex);
> >  }
> 
> I'd leave the clear_vmaster just for clarity. Commit should not be
> unpaired with prepare in the other functions.
> 

Ack. I'd like to pair prepare and commit as well. I'm just confused
about the check if (state->vmaster != master->vmaster). Maybe a helpful
comment about what are we checking for would make things cleaner.

With this nit:

Reviewed-by: Pranjal Shrivastavat <praan@...gle.com>

Thanks,
Praan