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From: Lu Baolu <baolu.lu@linux.intel.com>
To: David Woodhouse <dwmw2@infradead.org>, Joerg Roedel <joro@8bytes.org>
Cc: kevin.tian@intel.com, ashok.raj@intel.com,
	linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org
Subject: Re: [PATCH 0/5] iommu/vt-d: Consolidate various cache flush ops
Date: Wed, 4 Dec 2019 08:27:10 +0800
Message-ID: <4100ad7a-0818-7fc1-aaf5-bf0ef44f3f54@linux.intel.com> (raw)
In-Reply-To: <22759c43f440eecee60b2d318b6f8e8fe2587bcb.camel@infradead.org>

Hi David,

On 12/3/19 4:49 PM, David Woodhouse wrote:
> On Fri, 2019-11-22 at 11:04 +0800, Lu Baolu wrote:
>> Intel VT-d 3.0 introduces more caches and interfaces for software to
>> flush when it runs in the scalable mode. Currently various cache flush
>> helpers are scattered around. This consolidates them by putting them in
>> the existing iommu_flush structure.
>>
>> /* struct iommu_flush - Intel IOMMU cache invalidation ops
>>   *
>>   * @cc_inv: invalidate context cache
>>   * @iotlb_inv: Invalidate IOTLB and paging structure caches when software
>>   *             has changed second-level tables.
>>   * @p_iotlb_inv: Invalidate IOTLB and paging structure caches when software
>>   *               has changed first-level tables.
>>   * @pc_inv: invalidate pasid cache
>>   * @dev_tlb_inv: invalidate cached mappings used by requests-without-PASID
>>   *               from the Device-TLB on a endpoint device.
>>   * @p_dev_tlb_inv: invalidate cached mappings used by requests-with-PASID
>>   *                 from the Device-TLB on an endpoint device
>>   */
>> struct iommu_flush {
>>          void (*cc_inv)(struct intel_iommu *iommu, u16 did,
>>                         u16 sid, u8 fm, u64 type);
>>          void (*iotlb_inv)(struct intel_iommu *iommu, u16 did, u64 addr,
>>                            unsigned int size_order, u64 type);
>>          void (*p_iotlb_inv)(struct intel_iommu *iommu, u16 did, u32 pasid,
>>                              u64 addr, unsigned long npages, bool ih);
>>          void (*pc_inv)(struct intel_iommu *iommu, u16 did, u32 pasid,
>>                         u64 granu);
>>          void (*dev_tlb_inv)(struct intel_iommu *iommu, u16 sid, u16 pfsid,
>>                              u16 qdep, u64 addr, unsigned int mask);
>>          void (*p_dev_tlb_inv)(struct intel_iommu *iommu, u16 sid, u16 pfsid,
>>                                u32 pasid, u16 qdep, u64 addr,
>>                                unsigned long npages);
>> };
>>
>> The name of each cache flush ops is defined according to the spec section 6.5
>> so that people are easy to look up them in the spec.
> 
> Hm, indirect function calls are quite expensive these days.

Good consideration. Thanks!

> 
> I would have preferred to go in the opposite direction, since surely
> aren't going to have *many* of these implementations. Currently there's
> only one for register-based and one for queued invalidation, right?
> Even if VT-d 3.0 throws an extra version in, I think I'd prefer to take
> out the indirection completely and have an if/then helper.
> 
> Would love to see a microbenchmark of unmap operations before and after
> this patch series with retpoline enabled, to see the effect.

Yes. Need some micro-bench tests to address the concern.

Best regards,
baolu
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Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-22  3:04 Lu Baolu
2019-11-22  3:04 ` [PATCH 1/5] iommu/vt-d: Extend iommu_flush for scalable mode Lu Baolu
2019-11-22  3:04 ` [PATCH 2/5] iommu/vt-d: Consolidate pasid cache invalidation Lu Baolu
2019-11-22  3:04 ` [PATCH 3/5] iommu/vt-d: Consolidate device tlb invalidation Lu Baolu
2019-11-22  3:04 ` [PATCH 4/5] iommu/vt-d: Consolidate pasid-based " Lu Baolu
2019-12-03 17:43   ` Jacob Pan
2019-11-22  3:04 ` [PATCH 5/5] iommu/vt-d: Consolidate pasid-based device " Lu Baolu
2019-12-02 20:02 ` [PATCH 0/5] iommu/vt-d: Consolidate various cache flush ops Jacob Pan
2019-12-03  2:44   ` Lu Baolu
2019-12-03 16:50     ` Jacob Pan
2019-12-04  0:32       ` Lu Baolu
2019-12-04 17:41         ` Jacob Pan
2019-12-03  8:49 ` David Woodhouse
2019-12-04  0:27   ` Lu Baolu [this message]

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