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From: Marc Zyngier <maz@kernel.org>
To: Will Deacon <will@kernel.org>
Cc: Jean-Philippe Brucker <jean-philippe@linaro.org>,
	kevin.tian@intel.com, devicetree@vger.kernel.org, jgg@ziepe.ca,
	linux-pci@vger.kernel.org, fenghua.yu@intel.com,
	hch@infradead.org, linux-mm@kvack.org,
	iommu@lists.linux-foundation.org, zhangfei.gao@linaro.org,
	catalin.marinas@arm.com, felix.kuehling@amd.com,
	robin.murphy@arm.com, christian.koenig@amd.com,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v7 13/24] iommu/arm-smmu-v3: Enable broadcast TLB maintenance
Date: Thu, 21 May 2020 15:38:35 +0100	[thread overview]
Message-ID: <0c896ad27b43b2de554cf772f9453d0a@kernel.org> (raw)
In-Reply-To: <20200521141730.GJ6608@willie-the-truck>

On 2020-05-21 15:17, Will Deacon wrote:
> [+Marc]
> 
> On Tue, May 19, 2020 at 07:54:51PM +0200, Jean-Philippe Brucker wrote:
>> The SMMUv3 can handle invalidation targeted at TLB entries with shared
>> ASIDs. If the implementation supports broadcast TLB maintenance, 
>> enable it
>> and keep track of it in a feature bit. The SMMU will then be affected 
>> by
>> inner-shareable TLB invalidations from other agents.
>> 
>> A major side-effect of this change is that stage-2 translation 
>> contexts
>> are now affected by all invalidations by VMID. VMIDs are all shared 
>> and
>> the only ways to prevent over-invalidation, since the stage-2 page 
>> tables
>> are not shared between CPU and SMMU, are to either disable BTM or 
>> allocate
>> different VMIDs. This patch does not address the problem.
> 
> This sounds like a potential performance issue, particularly as we 
> expose
> stage-2 contexts via VFIO directly. Maybe we could reserve some portion 
> of
> VMID space for the SMMU? Marc, what do you reckon?

Certainly doable when we have 16bits VMIDs. With smaller VMID spaces 
(like on
v8.0), this is a bit more difficult (we do have pretty large v8.0 
systems
around). How many VMID bits are we talking about?

         M.
-- 
Jazz is not dead. It just smells funny...
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  reply	other threads:[~2020-05-21 14:38 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19 17:54 [PATCH v7 00/24] iommu: Shared Virtual Addressing for SMMUv3 Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 01/24] mm: Add a PASID field to mm_struct Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 02/24] iommu/ioasid: Add ioasid references Jean-Philippe Brucker
2020-05-20  2:31   ` Lu Baolu
2020-05-19 17:54 ` [PATCH v7 03/24] iommu/sva: Add PASID helpers Jean-Philippe Brucker
2020-05-20  2:41   ` Lu Baolu
2020-05-19 17:54 ` [PATCH v7 04/24] iommu: Add a page fault handler Jean-Philippe Brucker
2020-05-20  6:42   ` Lu Baolu
2020-11-11 13:57     ` Jean-Philippe Brucker
2020-11-11 23:11       ` Lu Baolu
2020-05-29  9:18   ` Xiang Zheng
2020-11-11 13:57     ` Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 05/24] arm64: mm: Add asid_gen_match() helper Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 06/24] arm64: mm: Pin down ASIDs for sharing mm with devices Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 07/24] iommu/io-pgtable-arm: Move some definitions to a header Jean-Philippe Brucker
2020-05-21 14:16   ` Will Deacon
2020-05-19 17:54 ` [PATCH v7 08/24] iommu/arm-smmu-v3: Manage ASIDs with xarray Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 09/24] arm64: cpufeature: Export symbol read_sanitised_ftr_reg() Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 10/24] iommu/arm-smmu-v3: Share process page tables Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 11/24] iommu/arm-smmu-v3: Seize private ASID Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 12/24] iommu/arm-smmu-v3: Add support for VHE Jean-Philippe Brucker
2020-05-21 14:16   ` Will Deacon
2020-05-19 17:54 ` [PATCH v7 13/24] iommu/arm-smmu-v3: Enable broadcast TLB maintenance Jean-Philippe Brucker
2020-05-21 14:17   ` Will Deacon
2020-05-21 14:38     ` Marc Zyngier [this message]
2020-05-22 10:17       ` Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 14/24] iommu/arm-smmu-v3: Add SVA feature checking Jean-Philippe Brucker
2020-05-21 14:17   ` Will Deacon
2020-05-19 17:54 ` [PATCH v7 15/24] iommu/arm-smmu-v3: Add SVA device feature Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 16/24] iommu/arm-smmu-v3: Implement iommu_sva_bind/unbind() Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 17/24] iommu/arm-smmu-v3: Hook up ATC invalidation to mm ops Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 18/24] iommu/arm-smmu-v3: Add support for Hardware Translation Table Update Jean-Philippe Brucker
2020-05-21 11:12   ` Will Deacon
2020-05-27  3:00   ` Xiang Zheng
2020-05-27  8:41     ` Jean-Philippe Brucker
2020-08-28  9:28   ` Zenghui Yu
2020-09-16 14:11     ` Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 19/24] iommu/arm-smmu-v3: Maintain a SID->device structure Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 20/24] dt-bindings: document stall property for IOMMU masters Jean-Philippe Brucker
2020-05-19 17:54 ` [PATCH v7 21/24] iommu/arm-smmu-v3: Add stall support for platform devices Jean-Philippe Brucker
2020-06-01 12:42   ` Shameerali Kolothum Thodi
2020-06-02  9:38     ` Jean-Philippe Brucker
2020-06-02 10:31       ` Shameerali Kolothum Thodi
2020-06-02 11:46         ` Jean-Philippe Brucker
2020-06-02 12:12           ` Shameerali Kolothum Thodi
2020-06-03  7:38             ` Jean-Philippe Brucker
2020-05-19 17:55 ` [PATCH v7 22/24] PCI/ATS: Add PRI stubs Jean-Philippe Brucker
2020-05-19 17:55 ` [PATCH v7 23/24] PCI/ATS: Export PRI functions Jean-Philippe Brucker
2020-05-19 17:55 ` [PATCH v7 24/24] iommu/arm-smmu-v3: Add support for PRI Jean-Philippe Brucker
2020-05-21 10:35 ` [PATCH v7 00/24] iommu: Shared Virtual Addressing for SMMUv3 Will Deacon
2020-05-21 14:17   ` Will Deacon

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