linux-kernel - Re: [PATCH v11 8/8] dmaengine/idxd: Re-enable kernel workqueue under DMA API

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Message-ID: <ZMptbm4BEmEP4Z1J@nvidia.com>
Date:   Wed, 2 Aug 2023 11:51:26 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will@...nel.org>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>, Tony Zhu <tony.zhu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>
Subject: Re: [PATCH v11 8/8] dmaengine/idxd: Re-enable kernel workqueue under
 DMA API

On Mon, Jul 24, 2023 at 03:25:38PM -0700, Jacob Pan wrote:
> Kernel workqueues were disabled due to flawed use of kernel VA and SVA
> API. Now that we have the support for attaching PASID to the device's
> default domain and the ability to reserve global PASIDs from SVA APIs,
> we can re-enable the kernel work queues and use them under DMA API.
> 
> We also use non-privileged access for in-kernel DMA to be consistent
> with the IOMMU settings. Consequently, interrupt for user privilege is
> enabled for work completion IRQs.
> 
> Link:https://lore.kernel.org/linux-iommu/20210511194726.GP1002214@nvidia.com/
> Tested-by: Tony Zhu <tony.zhu@...el.com>
> Reviewed-by: Dave Jiang <dave.jiang@...el.com>
> Reviewed-by: Fenghua Yu <fenghua.yu@...el.com>
> Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Acked-by: Vinod Koul <vkoul@...nel.org>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
> v9: Set user IRQ enable when device is enabled for system PASID
> ---
>  drivers/dma/idxd/device.c | 39 ++++++++++------------------
>  drivers/dma/idxd/dma.c    |  5 ++--
>  drivers/dma/idxd/idxd.h   |  9 +++++++
>  drivers/dma/idxd/init.c   | 54 ++++++++++++++++++++++++++++++++++++---
>  drivers/dma/idxd/sysfs.c  |  7 -----
>  5 files changed, 76 insertions(+), 38 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason