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From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Auger Eric <eric.auger@redhat.com>
Cc: fenghua.yu@intel.com, will@kernel.org, catalin.marinas@arm.com,
	zhengxiang9@huawei.com, linux-mm@kvack.org,
	iommu@lists.linux-foundation.org, zhangfei.gao@linaro.org,
	robin.murphy@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH RESEND v9 08/13] iommu/arm-smmu-v3: Share process page tables
Date: Thu, 17 Sep 2020 16:37:55 +0200	[thread overview]
Message-ID: <20200917143755.GC134903@myrica> (raw)
In-Reply-To: <496fbadf-a075-eed2-2dda-eeaaac35656e@redhat.com>

On Tue, Sep 08, 2020 at 09:41:20AM +0200, Auger Eric wrote:
> > +static struct arm_smmu_ctx_desc *arm_smmu_alloc_shared_cd(struct mm_struct *mm)
> > +{
> > +	u16 asid;
> > +	int err = 0;
> > +	u64 tcr, par, reg;
> > +	struct arm_smmu_ctx_desc *cd;
> > +	struct arm_smmu_ctx_desc *ret = NULL;
> > +
> > +	asid = arm64_mm_context_get(mm);
> > +	if (!asid)
> > +		return ERR_PTR(-ESRCH);
> > +
> > +	cd = kzalloc(sizeof(*cd), GFP_KERNEL);
> > +	if (!cd) {
> > +		err = -ENOMEM;
> > +		goto out_put_context;
> > +	}
> > +
> > +	refcount_set(&cd->refs, 1);
> > +
> > +	mutex_lock(&arm_smmu_asid_lock);
> > +	ret = arm_smmu_share_asid(mm, asid);
> > +	if (ret) {
> > +		mutex_unlock(&arm_smmu_asid_lock);
> > +		goto out_free_cd;
> > +	}
> > +
> > +	err = xa_insert(&arm_smmu_asid_xa, asid, cd, GFP_KERNEL);
> > +	mutex_unlock(&arm_smmu_asid_lock);
> I am not clear about the locking scope. Can't we release the lock before
> as if I understand correctly xa_insert/xa_erase takes the xa_lock.

The mutex prevents conflicts with the private ASID allocation:

	CPU 1					CPU 2
arm_smmu_alloc_shared_cd()		arm_smmu_attach_dev()
 arm_smmu_share_asid(mm, 1)		 arm_smmu_domain_finalise_s1()
  xa_load(&asid_xa, 1) -> NULL, ok
					  xa_alloc(&asid_xa) -> ASID #1
 xa_insert(&asid_xa, 1) -> error

> > +
> > +	if (err)
> > +		goto out_free_asid;
> > +
> > +	tcr = FIELD_PREP(CTXDESC_CD_0_TCR_T0SZ, 64ULL - VA_BITS) |
> Wondering if no additional check is needed to check if the T0SZ is valid
> as documented in 5.4 Context Descriptor T0SZ description.

Indeed, this code probably predates 52-bit VA support. Now patch 10 should
check the VA limits, and we should use vabits_actual rather than VA_BITS.
I'll leave out IDR3.STT for now because arch/arm64/ doesn't support it.

Thanks,
Jean
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  reply	other threads:[~2020-09-17 14:38 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-17 17:15 [PATCH RESEND v9 00/13] iommu: Shared Virtual Addressing for SMMUv3 (PT sharing part) Jean-Philippe Brucker
2020-08-17 17:15 ` [PATCH RESEND v9 01/13] mm: Define pasid in mm Jean-Philippe Brucker
2020-08-17 17:15 ` [PATCH RESEND v9 02/13] iommu/ioasid: Add ioasid references Jean-Philippe Brucker
2020-09-08  9:52   ` Auger Eric
2020-08-17 17:15 ` [PATCH RESEND v9 03/13] iommu/sva: Add PASID helpers Jean-Philippe Brucker
2020-09-08  7:45   ` Auger Eric
2020-09-17 14:36     ` Jean-Philippe Brucker
2020-08-17 17:15 ` [PATCH RESEND v9 04/13] arm64: mm: Pin down ASIDs for sharing mm with devices Jean-Philippe Brucker
2020-08-17 17:15 ` [PATCH RESEND v9 05/13] iommu/io-pgtable-arm: Move some definitions to a header Jean-Philippe Brucker
2020-08-17 17:15 ` [PATCH RESEND v9 06/13] arm64: cpufeature: Export symbol read_sanitised_ftr_reg() Jean-Philippe Brucker
2020-08-17 17:15 ` [PATCH RESEND v9 07/13] iommu/arm-smmu-v3: Move definitions to a header Jean-Philippe Brucker
2020-09-08  9:16   ` Auger Eric
2020-08-17 17:15 ` [PATCH RESEND v9 08/13] iommu/arm-smmu-v3: Share process page tables Jean-Philippe Brucker
2020-09-08  7:41   ` Auger Eric
2020-09-17 14:37     ` Jean-Philippe Brucker [this message]
2020-08-17 17:15 ` [PATCH RESEND v9 09/13] iommu/arm-smmu-v3: Seize private ASID Jean-Philippe Brucker
2020-09-07 16:41   ` Auger Eric
2020-09-17 14:38     ` Jean-Philippe Brucker
2020-08-17 17:15 ` [PATCH RESEND v9 10/13] iommu/arm-smmu-v3: Check for SVA features Jean-Philippe Brucker
2020-09-08  9:38   ` Auger Eric
2020-09-17 14:39     ` Jean-Philippe Brucker
2020-08-17 17:15 ` [PATCH RESEND v9 11/13] iommu/arm-smmu-v3: Add SVA device feature Jean-Philippe Brucker
2020-09-08  9:46   ` Auger Eric
2020-09-17 14:40     ` Jean-Philippe Brucker
2020-08-17 17:15 ` [PATCH RESEND v9 12/13] iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind() Jean-Philippe Brucker
2020-08-17 17:15 ` [PATCH RESEND v9 13/13] iommu/arm-smmu-v3: Hook up ATC invalidation to mm ops Jean-Philippe Brucker
2020-09-04  9:08 ` [PATCH RESEND v9 00/13] iommu: Shared Virtual Addressing for SMMUv3 (PT sharing part) Joerg Roedel
2020-09-17 14:36   ` Jean-Philippe Brucker

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