From: Jean-Philippe Brucker <jean-philippe@linaro.org>
To: Auger Eric <eric.auger@redhat.com>
Cc: fenghua.yu@intel.com, will@kernel.org,
Suzuki K Poulose <suzuki.poulose@arm.com>,
catalin.marinas@arm.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 10/13] iommu/arm-smmu-v3: Check for SVA features
Date: Thu, 17 Sep 2020 16:39:51 +0200 [thread overview]
Message-ID: <20200917143951.GE134903@myrica> (raw)
In-Reply-To: <d8cef101-fae8-eead-a898-1fca5fe4faaf@redhat.com>
On Tue, Sep 08, 2020 at 11:38:31AM +0200, Auger Eric wrote:
> Hi Jean,
> On 8/17/20 7:15 PM, Jean-Philippe Brucker wrote:
> > Aggregate all sanity-checks for sharing CPU page tables with the SMMU
> > under a single ARM_SMMU_FEAT_SVA bit. For PCIe SVA, users also need to
> > check FEAT_ATS and FEAT_PRI. For platform SVA, they will have to check
> > FEAT_STALLS.
> >
> > Introduce ARM_SMMU_FEAT_BTM (Broadcast TLB Maintenance), but don't
> > enable it at the moment. Since the entire VMID space is shared with the
> > CPU, enabling DVM (by clearing SMMU_CR2.PTM) could result in
> > over-invalidation and affect performance of stage-2 mappings.
> In which series do you plan to enable it?
In the third part, after the PRI+stall series. I still haven't had time to
look at solving the stage-2 DVM problem (pinning VMIDs through KVM), so it
might be a while.
[...]
> > + /*
> > + * See max_pinned_asids in arch/arm64/mm/context.c. The following is
> > + * generally the maximum number of bindable processes.
> > + */
> > + if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0))
> Out of curiosity, What is the rationale behind using
> arm64_kernel_unmapped_at_el0() versus
> IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0)?
> CPU caps being finalized?
I'm not sure. The caps are finalized at this point. I'll change it.
> Is that why you say "generally" here?
I said "generally" because having less PASIDs than ASIDs is in theory
possible, but hardware will normally support 20-bit PASIDs.
> > + asid_bits--;
> > + dev_dbg(smmu->dev, "%d shared contexts\n", (1 << asid_bits) -> + num_possible_cpus() - 2);
> nit: s/shared/bindable?
I find "shared" clearer, with regard to contexts
Thanks,
Jean
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next prev parent reply other threads:[~2020-09-17 14:40 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
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 [this message]
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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