From: Lu Baolu <baolu.lu@linux.intel.com> To: Jason Gunthorpe <jgg@nvidia.com>, Joerg Roedel <joro@8bytes.org> Cc: baolu.lu@linux.intel.com, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Alex Williamson <alex.williamson@redhat.com>, Bjorn Helgaas <bhelgaas@google.com>, Christoph Hellwig <hch@infradead.org>, Kevin Tian <kevin.tian@intel.com>, Ashok Raj <ashok.raj@intel.com>, Will Deacon <will@kernel.org>, Robin Murphy <robin.murphy@arm.com>, Dan Williams <dan.j.williams@intel.com>, rafael@kernel.org, Diana Craciun <diana.craciun@oss.nxp.com>, Cornelia Huck <cohuck@redhat.com>, Eric Auger <eric.auger@redhat.com>, Liu Yi L <yi.l.liu@intel.com>, Jacob jun Pan <jacob.jun.pan@intel.com>, Chaitanya Kulkarni <kch@nvidia.com>, Stuart Yoder <stuyoder@gmail.com>, Laurentiu Tudor <laurentiu.tudor@nxp.com>, Thierry Reding <thierry.reding@gmail.com>, David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>, Jonathan Hunter <jonathanh@nvidia.com>, Li Yang <leoyang.li@nxp.com>, Dmitry Osipenko <digetx@gmail.com>, iommu@lists.linux-foundation.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 01/18] iommu: Add device dma ownership set/release interfaces Date: Tue, 7 Dec 2021 09:52:37 +0800 [thread overview] Message-ID: <fa30d398-746c-c7d0-830f-40e3aaee16d6@linux.intel.com> (raw) In-Reply-To: <20211206150144.GC4670@nvidia.com> On 12/6/21 11:01 PM, Jason Gunthorpe wrote: > On Mon, Dec 06, 2021 at 02:35:55PM +0100, Joerg Roedel wrote: >> On Mon, Dec 06, 2021 at 09:58:46AM +0800, Lu Baolu wrote: >>> >From the perspective of who is initiating the device to do DMA, device >>> DMA could be divided into the following types: >>> >>> DMA_OWNER_DMA_API: Device DMAs are initiated by a kernel driver >>> through the kernel DMA API. >>> DMA_OWNER_PRIVATE_DOMAIN: Device DMAs are initiated by a kernel >>> driver with its own PRIVATE domain. >>> DMA_OWNER_PRIVATE_DOMAIN_USER: Device DMAs are initiated by >>> userspace. >> >> I have looked at the other iommu patches in this series, but I still >> don't quite get what the difference in the code flow is between >> DMA_OWNER_PRIVATE_DOMAIN and DMA_OWNER_PRIVATE_DOMAIN_USER. What are the >> differences in the iommu core behavior based on this setting? > > USER causes the IOMMU code to spend extra work to never assign the > default domain. Lu, it would be good to update the comment with this > detail > > Once in USER mode the domain is always a /dev/null domain or a domain > controlled by userspace. Never a domain pointing at kernel memory. Yes. The __iommu_detach_group() re-attaches the default domain automatically. This is not allowed once in USER mode. I will update the comments whit this detail. > >>> struct group_device { >>> @@ -621,6 +624,7 @@ struct iommu_group *iommu_group_alloc(void) >>> INIT_LIST_HEAD(&group->devices); >>> INIT_LIST_HEAD(&group->entry); >>> BLOCKING_INIT_NOTIFIER_HEAD(&group->notifier); >>> + group->dma_owner = DMA_OWNER_NONE; >> >> >> DMA_OWNER_NONE is also questionable. All devices are always in one >> domain, and the default domain is always the one used for DMA-API, so >> why isn't the initial value DMA_OWNER_DMA_API? > > 'NONE' means the group is in the default domain but no driver is bound > and thus DMA isn't being used. Seeing NONE is the only condition when > it is OK to change the domain. > > This could be reworked to instead rely on the refcount == 0 as the > signal to know it is OK to change the domain and then we never have > NONE at all. Lu? NONE is just a parking state. It's okay to rely on the "refcount == 0" for state transition as far as I see. I will work towards this. Best regards, baolu
WARNING: multiple messages have this Message-ID (diff)
From: Lu Baolu <baolu.lu@linux.intel.com> To: Jason Gunthorpe <jgg@nvidia.com>, Joerg Roedel <joro@8bytes.org> Cc: Stuart Yoder <stuyoder@gmail.com>, rafael@kernel.org, David Airlie <airlied@linux.ie>, linux-pci@vger.kernel.org, Thierry Reding <thierry.reding@gmail.com>, Diana Craciun <diana.craciun@oss.nxp.com>, Dmitry Osipenko <digetx@gmail.com>, Will Deacon <will@kernel.org>, Ashok Raj <ashok.raj@intel.com>, Jonathan Hunter <jonathanh@nvidia.com>, Christoph Hellwig <hch@infradead.org>, Kevin Tian <kevin.tian@intel.com>, Chaitanya Kulkarni <kch@nvidia.com>, Alex Williamson <alex.williamson@redhat.com>, kvm@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>, Dan Williams <dan.j.williams@intel.com>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Cornelia Huck <cohuck@redhat.com>, linux-kernel@vger.kernel.org, Li Yang <leoyang.li@nxp.com>, iommu@lists.linux-foundation.org, Jacob jun Pan <jacob.jun.pan@intel.com>, Daniel Vetter <daniel@ffwll.ch>, Robin Murphy <robin.murphy@arm.com> Subject: Re: [PATCH v3 01/18] iommu: Add device dma ownership set/release interfaces Date: Tue, 7 Dec 2021 09:52:37 +0800 [thread overview] Message-ID: <fa30d398-746c-c7d0-830f-40e3aaee16d6@linux.intel.com> (raw) In-Reply-To: <20211206150144.GC4670@nvidia.com> On 12/6/21 11:01 PM, Jason Gunthorpe wrote: > On Mon, Dec 06, 2021 at 02:35:55PM +0100, Joerg Roedel wrote: >> On Mon, Dec 06, 2021 at 09:58:46AM +0800, Lu Baolu wrote: >>> >From the perspective of who is initiating the device to do DMA, device >>> DMA could be divided into the following types: >>> >>> DMA_OWNER_DMA_API: Device DMAs are initiated by a kernel driver >>> through the kernel DMA API. >>> DMA_OWNER_PRIVATE_DOMAIN: Device DMAs are initiated by a kernel >>> driver with its own PRIVATE domain. >>> DMA_OWNER_PRIVATE_DOMAIN_USER: Device DMAs are initiated by >>> userspace. >> >> I have looked at the other iommu patches in this series, but I still >> don't quite get what the difference in the code flow is between >> DMA_OWNER_PRIVATE_DOMAIN and DMA_OWNER_PRIVATE_DOMAIN_USER. What are the >> differences in the iommu core behavior based on this setting? > > USER causes the IOMMU code to spend extra work to never assign the > default domain. Lu, it would be good to update the comment with this > detail > > Once in USER mode the domain is always a /dev/null domain or a domain > controlled by userspace. Never a domain pointing at kernel memory. Yes. The __iommu_detach_group() re-attaches the default domain automatically. This is not allowed once in USER mode. I will update the comments whit this detail. > >>> struct group_device { >>> @@ -621,6 +624,7 @@ struct iommu_group *iommu_group_alloc(void) >>> INIT_LIST_HEAD(&group->devices); >>> INIT_LIST_HEAD(&group->entry); >>> BLOCKING_INIT_NOTIFIER_HEAD(&group->notifier); >>> + group->dma_owner = DMA_OWNER_NONE; >> >> >> DMA_OWNER_NONE is also questionable. All devices are always in one >> domain, and the default domain is always the one used for DMA-API, so >> why isn't the initial value DMA_OWNER_DMA_API? > > 'NONE' means the group is in the default domain but no driver is bound > and thus DMA isn't being used. Seeing NONE is the only condition when > it is OK to change the domain. > > This could be reworked to instead rely on the refcount == 0 as the > signal to know it is OK to change the domain and then we never have > NONE at all. Lu? NONE is just a parking state. It's okay to rely on the "refcount == 0" for state transition as far as I see. I will work towards this. Best regards, baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
next prev parent reply other threads:[~2021-12-07 1:52 UTC|newest] Thread overview: 102+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-12-06 1:58 [PATCH v3 00/18] Fix BUG_ON in vfio_iommu_group_notifier() Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 01/18] iommu: Add device dma ownership set/release interfaces Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 13:35 ` Joerg Roedel 2021-12-06 13:35 ` Joerg Roedel 2021-12-06 14:29 ` Christoph Hellwig 2021-12-06 14:29 ` Christoph Hellwig 2021-12-06 15:01 ` Jason Gunthorpe 2021-12-06 15:01 ` Jason Gunthorpe via iommu 2021-12-07 1:52 ` Lu Baolu [this message] 2021-12-07 1:52 ` Lu Baolu 2021-12-06 14:42 ` Christoph Hellwig 2021-12-06 14:42 ` Christoph Hellwig 2021-12-07 2:07 ` Lu Baolu 2021-12-07 2:07 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 02/18] driver core: Add dma_cleanup callback in bus_type Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 03/18] driver core: platform: Rename platform_dma_configure() Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 7:53 ` Greg Kroah-Hartman 2021-12-06 7:53 ` Greg Kroah-Hartman 2021-12-06 14:13 ` Christoph Hellwig 2021-12-06 14:13 ` Christoph Hellwig 2021-12-06 14:43 ` Greg Kroah-Hartman 2021-12-06 14:43 ` Greg Kroah-Hartman 2021-12-06 14:45 ` Jason Gunthorpe 2021-12-06 14:45 ` Jason Gunthorpe via iommu 2021-12-06 14:47 ` Christoph Hellwig 2021-12-06 14:47 ` Christoph Hellwig 2021-12-06 15:04 ` Jason Gunthorpe via iommu 2021-12-06 15:04 ` Jason Gunthorpe 2021-12-07 1:21 ` Lu Baolu 2021-12-07 1:21 ` Lu Baolu 2021-12-07 23:09 ` Dan Williams 2021-12-07 23:09 ` Dan Williams 2021-12-06 1:58 ` [PATCH v3 04/18] driver core: platform: Add driver dma ownership management Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 7:54 ` Greg Kroah-Hartman 2021-12-06 7:54 ` Greg Kroah-Hartman 2021-12-06 14:36 ` Christoph Hellwig 2021-12-06 14:36 ` Christoph Hellwig 2021-12-06 15:06 ` Jason Gunthorpe via iommu 2021-12-06 15:06 ` Jason Gunthorpe 2021-12-07 2:57 ` Lu Baolu 2021-12-07 2:57 ` Lu Baolu 2021-12-07 13:16 ` Jason Gunthorpe 2021-12-07 13:16 ` Jason Gunthorpe via iommu 2021-12-07 13:25 ` Christoph Hellwig 2021-12-07 13:25 ` Christoph Hellwig 2021-12-07 13:30 ` Jason Gunthorpe 2021-12-07 13:30 ` Jason Gunthorpe via iommu 2021-12-09 1:20 ` Lu Baolu 2021-12-09 1:20 ` Lu Baolu 2021-12-10 1:23 ` Lu Baolu 2021-12-10 1:23 ` Lu Baolu 2021-12-13 0:50 ` Lu Baolu 2021-12-13 0:50 ` Lu Baolu 2021-12-13 13:24 ` Jason Gunthorpe 2021-12-13 13:24 ` Jason Gunthorpe via iommu 2021-12-15 12:24 ` Lu Baolu 2021-12-15 12:24 ` Lu Baolu 2021-12-14 16:35 ` Christoph Hellwig 2021-12-14 16:35 ` Christoph Hellwig 2021-12-06 1:58 ` [PATCH v3 05/18] amba: " Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 06/18] bus: fsl-mc: " Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 07/18] PCI: " Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 08/18] PCI: pci_stub: Suppress kernel DMA ownership auto-claiming Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 09/18] PCI: portdrv: " Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 10/18] iommu: Add security context management for assigned devices Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 11/18] iommu: Expose group variants of dma ownership interfaces Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 12/18] iommu: Add iommu_at[de]tach_device_shared() for multi-device groups Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 14:43 ` Christoph Hellwig 2021-12-06 14:43 ` Christoph Hellwig 2021-12-07 2:33 ` Lu Baolu 2021-12-07 2:33 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 13/18] vfio: Set DMA USER ownership for VFIO devices Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 1:58 ` [PATCH v3 14/18] vfio: Remove use of vfio_group_viable() Lu Baolu 2021-12-06 1:58 ` Lu Baolu 2021-12-06 1:59 ` [PATCH v3 15/18] vfio: Delete the unbound_list Lu Baolu 2021-12-06 1:59 ` Lu Baolu 2021-12-06 1:59 ` [PATCH v3 16/18] vfio: Remove iommu group notifier Lu Baolu 2021-12-06 1:59 ` Lu Baolu 2021-12-06 1:59 ` [PATCH v3 17/18] iommu: Remove iommu group changes notifier Lu Baolu 2021-12-06 1:59 ` Lu Baolu 2021-12-06 1:59 ` [PATCH v3 18/18] drm/tegra: Use the iommu dma_owner mechanism Lu Baolu 2021-12-06 1:59 ` Lu Baolu 2021-12-06 12:40 ` Jason Gunthorpe 2021-12-06 12:40 ` Jason Gunthorpe via iommu 2021-12-07 2:34 ` Lu Baolu 2021-12-07 2:34 ` Lu Baolu 2021-12-17 6:41 ` [PATCH v3 00/18] Fix BUG_ON in vfio_iommu_group_notifier() Lu Baolu 2021-12-17 6:41 ` Lu Baolu
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