From: Jason Gunthorpe <jgg@nvidia.com>
To: Pranjal Shrivastava <praan@google.com>
Cc: Nicolin Chen <nicolinc@nvidia.com>,
kevin.tian@intel.com, corbet@lwn.net, will@kernel.org,
bagasdotme@gmail.com, robin.murphy@arm.com, joro@8bytes.org,
thierry.reding@gmail.com, vdumpa@nvidia.com,
jonathanh@nvidia.com, shuah@kernel.org, jsnitsel@redhat.com,
nathan@kernel.org, peterz@infradead.org, yi.l.liu@intel.com,
mshavit@google.com, zhangzekun11@huawei.com,
iommu@lists.linux.dev, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-tegra@vger.kernel.org, linux-kselftest@vger.kernel.org,
patches@lists.linux.dev, mochs@nvidia.com,
alok.a.tiwari@oracle.com, vasant.hegde@amd.com,
dwmw2@infradead.org, baolu.lu@linux.intel.com
Subject: Re: [PATCH v7 27/28] iommu/tegra241-cmdqv: Add user-space use support
Date: Thu, 3 Jul 2025 14:55:32 -0300 [thread overview]
Message-ID: <20250703175532.GF1209783@nvidia.com> (raw)
In-Reply-To: <aGaXqwzfLwsgCH6n@google.com>
On Thu, Jul 03, 2025 at 02:46:03PM +0000, Pranjal Shrivastava wrote:
> Right.. I was however hoping we'd also trap commands like CMD_PRI_RESP
> and CMD_RESUME...I'm not sure if they should be accelerated via CMDQV..
> I guess I'll need to look and understand a little more if they are..
Right now these commands are not supported by vSMMUv3 in Linux.
They probably should be trapped, but completing a PRI (or resuming a
stall which we will treat the same) will go through the PRI/page fault
logic in iommufd not the cache invalidate.
> > The goal of the SMMU driver when it detects CMDQV support is to route
> > all supported invalidations to CMDQV queues and then balance those
> > queues across CPUs to reduce lock contention.
>
> I see.. that makes sense.. so it's a relatively small gain (but a nice
> one). Thanks for clarifying!
On bare metal the gain is small (due to locking and balancing), while
on virtualization the gain is huge (due to no trapping).
Regardless the SMMU driver uses cmdqv support if the HW says it is
there.
Jason
next prev parent reply other threads:[~2025-07-03 21:19 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-26 19:34 [PATCH v7 00/28] iommufd: Add vIOMMU infrastructure (Part-4 HW QUEUE) Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 01/28] iommufd: Report unmapped bytes in the error path of iopt_unmap_iova_range Nicolin Chen
2025-07-02 9:39 ` Tian, Kevin
2025-07-04 12:59 ` Jason Gunthorpe
2025-06-26 19:34 ` [PATCH v7 02/28] iommufd/viommu: Explicitly define vdev->virt_id Nicolin Chen
2025-07-01 12:30 ` Pranjal Shrivastava
2025-07-02 9:40 ` Tian, Kevin
2025-07-02 19:59 ` Nicolin Chen
2025-07-04 12:59 ` Jason Gunthorpe
2025-06-26 19:34 ` [PATCH v7 03/28] iommu: Use enum iommu_hw_info_type for type in hw_info op Nicolin Chen
2025-07-01 12:48 ` Pranjal Shrivastava
2025-07-01 12:51 ` Pranjal Shrivastava
2025-07-02 9:41 ` Tian, Kevin
2025-07-04 13:00 ` Jason Gunthorpe
2025-06-26 19:34 ` [PATCH v7 04/28] iommu: Add iommu_copy_struct_to_user helper Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 05/28] iommu: Pass in a driver-level user data structure to viommu_init op Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 06/28] iommufd/viommu: Allow driver-specific user data for a vIOMMU object Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 07/28] iommufd/selftest: Support user_data in mock_viommu_alloc Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 08/28] iommufd/selftest: Add coverage for viommu data Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 09/28] iommufd/access: Add internal APIs for HW queue to use Nicolin Chen
2025-07-02 9:42 ` Tian, Kevin
2025-07-04 13:08 ` Jason Gunthorpe
2025-06-26 19:34 ` [PATCH v7 10/28] iommufd/access: Bypass access->ops->unmap for internal use Nicolin Chen
2025-07-02 9:45 ` Tian, Kevin
2025-07-02 20:12 ` Nicolin Chen
2025-07-03 4:57 ` Tian, Kevin
2025-07-04 4:08 ` Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 11/28] iommufd/viommu: Add driver-defined vDEVICE support Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 12/28] iommufd/viommu: Introduce IOMMUFD_OBJ_HW_QUEUE and its related struct Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 13/28] iommufd/viommu: Add IOMMUFD_CMD_HW_QUEUE_ALLOC ioctl Nicolin Chen
2025-07-04 13:26 ` Jason Gunthorpe
2025-07-04 13:33 ` Jason Gunthorpe
2025-06-26 19:34 ` [PATCH v7 14/28] iommufd/driver: Add iommufd_hw_queue_depend/undepend() helpers Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 15/28] iommufd/selftest: Add coverage for IOMMUFD_CMD_HW_QUEUE_ALLOC Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 16/28] iommufd: Add mmap interface Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 17/28] iommufd/selftest: Add coverage for the new " Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 18/28] Documentation: userspace-api: iommufd: Update HW QUEUE Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 19/28] iommu: Allow an input type in hw_info op Nicolin Chen
2025-07-01 12:54 ` Pranjal Shrivastava
2025-06-26 19:34 ` [PATCH v7 20/28] iommufd: Allow an input data_type via iommu_hw_info Nicolin Chen
2025-07-01 12:58 ` Pranjal Shrivastava
2025-06-26 19:34 ` [PATCH v7 21/28] iommufd/selftest: Update hw_info coverage for an input data_type Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 22/28] iommu/arm-smmu-v3-iommufd: Add vsmmu_size/type and vsmmu_init impl ops Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 23/28] iommu/arm-smmu-v3-iommufd: Add hw_info to impl_ops Nicolin Chen
2025-07-01 12:24 ` Pranjal Shrivastava
2025-06-26 19:34 ` [PATCH v7 24/28] iommu/tegra241-cmdqv: Use request_threaded_irq Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 25/28] iommu/tegra241-cmdqv: Simplify deinit flow in tegra241_cmdqv_remove_vintf() Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 26/28] iommu/tegra241-cmdqv: Do not statically map LVCMDQs Nicolin Chen
2025-06-26 19:34 ` [PATCH v7 27/28] iommu/tegra241-cmdqv: Add user-space use support Nicolin Chen
2025-07-01 16:02 ` Pranjal Shrivastava
2025-07-01 19:42 ` Nicolin Chen
2025-07-01 20:03 ` Pranjal Shrivastava
2025-07-01 20:23 ` Nicolin Chen
2025-07-01 20:43 ` Pranjal Shrivastava
2025-07-01 22:07 ` Nicolin Chen
2025-07-01 22:51 ` Pranjal Shrivastava
2025-07-01 23:01 ` Nicolin Chen
2025-07-02 0:14 ` Pranjal Shrivastava
2025-07-02 0:46 ` Nicolin Chen
2025-07-02 1:38 ` Pranjal Shrivastava
2025-07-02 18:05 ` Jason Gunthorpe
2025-07-03 14:46 ` Pranjal Shrivastava
2025-07-03 17:55 ` Jason Gunthorpe [this message]
2025-07-03 18:48 ` Pranjal Shrivastava
2025-07-04 12:50 ` Jason Gunthorpe
2025-07-10 9:04 ` Pranjal Shrivastava
2025-06-26 19:34 ` [PATCH v7 28/28] iommu/tegra241-cmdqv: Add IOMMU_VEVENTQ_TYPE_TEGRA241_CMDQV support Nicolin Chen
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