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From: Jason Gunthorpe <jgg@nvidia.com>
To: Michael Shavit <mshavit@google.com>
Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, will@kernel.org,
	robin.murphy@arm.com, nicolinc@nvidia.com,
	jean-philippe@linaro.org, tina.zhang@intel.com,
	Joerg Roedel <joro@8bytes.org>, Kevin Tian <kevin.tian@intel.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Lu Baolu <baolu.lu@linux.intel.com>,
	Mark Brown <broonie@kernel.org>, Tomas Krcka <krckatom@amazon.de>,
	Yicong Yang <yangyicong@hisilicon.com>
Subject: Re: [PATCH v1 0/3] Clean-up arm-smmu-v3-sva.c: remove arm_smmu_bond
Date: Tue, 5 Sep 2023 09:35:28 -0300	[thread overview]
Message-ID: <ZPcgkO7omYremwyV@nvidia.com> (raw)
In-Reply-To: <20230905115013.1572240-1-mshavit@google.com>

On Tue, Sep 05, 2023 at 07:49:11PM +0800, Michael Shavit wrote:
> 
> This small series was originally part of a larger effort to support
> set_dev_pasid in arm-smmu-v3.c and a related SVA refactoring. But it can
> also stand on its own as an initial and prepatory clean-up.
> 
> The crux of this series relies on the observation that SVA won't
> allocate multiple SVA domains for the same device and mm pair. 

Yes, I think that is true, certainly no-intree user of this stuff
wants to do that.

It is enforced to be true after Tina's series:

https://lore.kernel.org/r/20230905000930.24515-1-tina.zhang@intel.com

Which makes one SVA domain per mm.

> There's therefore no reason for the driver to try to normalize data
> allocated for a device/mm pair across set_dev_pasid calls. 

Indeed, this is where we are trying to get to. This de-duplication
code in every driver is quite horrible.

> Note that arm-smmu-v3-sva performs a second level of normalization by
> mapping multiple bonds (now SVA domains) attached to devices with the
> same SMMU (if those devices have the same RID domain attached) to a
> single arm_smmu_mmu_notifier. This is not affected by these patches.

Ultimately the notifier should be per-iommu_domain as well.

Thanks,
Jason

WARNING: multiple messages have this Message-ID (diff)
From: Jason Gunthorpe <jgg@nvidia.com>
To: Michael Shavit <mshavit@google.com>
Cc: iommu@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, will@kernel.org,
	robin.murphy@arm.com, nicolinc@nvidia.com,
	jean-philippe@linaro.org, tina.zhang@intel.com,
	Joerg Roedel <joro@8bytes.org>, Kevin Tian <kevin.tian@intel.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	Lu Baolu <baolu.lu@linux.intel.com>,
	Mark Brown <broonie@kernel.org>, Tomas Krcka <krckatom@amazon.de>,
	Yicong Yang <yangyicong@hisilicon.com>
Subject: Re: [PATCH v1 0/3] Clean-up arm-smmu-v3-sva.c: remove arm_smmu_bond
Date: Tue, 5 Sep 2023 09:35:28 -0300	[thread overview]
Message-ID: <ZPcgkO7omYremwyV@nvidia.com> (raw)
In-Reply-To: <20230905115013.1572240-1-mshavit@google.com>

On Tue, Sep 05, 2023 at 07:49:11PM +0800, Michael Shavit wrote:
> 
> This small series was originally part of a larger effort to support
> set_dev_pasid in arm-smmu-v3.c and a related SVA refactoring. But it can
> also stand on its own as an initial and prepatory clean-up.
> 
> The crux of this series relies on the observation that SVA won't
> allocate multiple SVA domains for the same device and mm pair. 

Yes, I think that is true, certainly no-intree user of this stuff
wants to do that.

It is enforced to be true after Tina's series:

https://lore.kernel.org/r/20230905000930.24515-1-tina.zhang@intel.com

Which makes one SVA domain per mm.

> There's therefore no reason for the driver to try to normalize data
> allocated for a device/mm pair across set_dev_pasid calls. 

Indeed, this is where we are trying to get to. This de-duplication
code in every driver is quite horrible.

> Note that arm-smmu-v3-sva performs a second level of normalization by
> mapping multiple bonds (now SVA domains) attached to devices with the
> same SMMU (if those devices have the same RID domain attached) to a
> single arm_smmu_mmu_notifier. This is not affected by these patches.

Ultimately the notifier should be per-iommu_domain as well.

Thanks,
Jason

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  parent reply	other threads:[~2023-09-05 12:35 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-09-05 11:49 [PATCH v1 0/3] Clean-up arm-smmu-v3-sva.c: remove arm_smmu_bond Michael Shavit
2023-09-05 11:49 ` Michael Shavit
2023-09-05 11:49 ` [PATCH v1 1/3] iommu/arm-smmu-v3-sva: Remove unused iommu_sva handle Michael Shavit
2023-09-05 11:49   ` Michael Shavit
2023-09-05 12:36   ` Jason Gunthorpe
2023-09-05 12:36     ` Jason Gunthorpe
2023-09-05 11:49 ` [PATCH v1 2/3] iommu/arm-smmu-v3-sva: Remove bond refcount Michael Shavit
2023-09-05 11:49   ` Michael Shavit
2023-09-05 12:38   ` Jason Gunthorpe
2023-09-05 12:38     ` Jason Gunthorpe
2023-09-05 11:49 ` [PATCH v1 3/3] iommu/arm-smmu-v3-sva: Remove arm_smmu_bond Michael Shavit
2023-09-05 11:49   ` Michael Shavit
2023-09-05 12:42   ` Jason Gunthorpe
2023-09-05 12:42     ` Jason Gunthorpe
2023-09-05 13:14     ` Michael Shavit
2023-09-05 13:14       ` Michael Shavit
2023-09-05 18:16       ` Jason Gunthorpe
2023-09-05 18:16         ` Jason Gunthorpe
2023-09-05 12:35 ` Jason Gunthorpe [this message]
2023-09-05 12:35   ` [PATCH v1 0/3] Clean-up arm-smmu-v3-sva.c: remove arm_smmu_bond Jason Gunthorpe
2023-09-05 13:24   ` Michael Shavit
2023-09-05 13:24     ` Michael Shavit
2023-09-05 13:32     ` Jason Gunthorpe
2023-09-05 13:32       ` Jason Gunthorpe
2023-10-12 18:06 ` Will Deacon
2023-10-12 18:06   ` Will Deacon

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