linux-kernel - Re: [PATCH v3 6/8] iommu/arm-smmu-v3: Move CD table to arm_smmu

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Message-ID: <ZMma/qk0otN9eyW3@nvidia.com>
Date:   Tue, 1 Aug 2023 20:53:34 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Michael Shavit <mshavit@...gle.com>
Cc:     iommu@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, robin.murphy@....com,
        will@...nel.org, jean-philippe@...aro.org, nicolinc@...dia.com
Subject: Re: [PATCH v3 6/8] iommu/arm-smmu-v3: Move CD table to
 arm_smmu_master

On Wed, Aug 02, 2023 at 02:35:23AM +0800, Michael Shavit wrote:
> @@ -2465,6 +2440,22 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>  	if (smmu_domain->stage != ARM_SMMU_DOMAIN_BYPASS)
>  		master->ats_enabled = arm_smmu_ats_supported(master);
>  
> +	if (smmu_domain->stage == ARM_SMMU_DOMAIN_S1) {
> +		if (!master->cd_table.cdtab) {
> +			ret = arm_smmu_alloc_cd_tables(master);
> +			if (ret) {

Again, I didn't look very closely at your locking, but what lock is
being held to protect the read of master->cd_table.cdtab ?

> +				master->domain = NULL;
> +				goto out_unlock;

This is only the domain lock:
	mutex_unlock(&smmu_domain->init_mutex);

Which is no longer sufficient.

You need some kind of lock in the master struct to protect the shared
cd table and everything in it?

Jason