Messages in this thread | | | Date | Wed, 18 Oct 2023 10:13:51 +0800 | Subject | Re: [PATCH v8 0/5] Share sva domains with all devices bound to a mm | From | Baolu Lu <> |
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On 10/18/23 12:41 AM, Jason Gunthorpe wrote: > On Tue, Oct 17, 2023 at 08:47:57AM +0800, Tina Zhang wrote: >> This series is to share sva(shared virtual addressing) domains with all >> devices bound to one mm. >> >> Problem >> ------- >> In the current iommu core code, sva domain is allocated per IOMMU group, >> when device driver is binding a process address space to a device (which is >> handled in iommu_sva_bind_device()). If one than more device is bound to >> the same process address space, there must be more than one sva domain >> instance, with each device having one. In other words, the sva domain >> doesn't share between those devices bound to the same process address >> space, and that leads to two problems: >> 1) device driver has to duplicate sva domains with enqcmd, as those sva >> domains have the same PASID and are relevant to one virtual address space. >> This makes the sva domain handling complex in device drivers. >> 2) IOMMU driver cannot get sufficient info of the IOMMUs that have >> devices behind them bound to the same virtual address space, when handling >> mmu_notifier_ops callbacks. As a result, IOMMU IOTLB invalidation is >> performed per device instead of per IOMMU, and that may lead to >> superfluous IOTLB invalidation issue, especially in a virtualization >> environment where all devices may be behind one virtual IOMMU. >> >> Solution >> -------- >> This patch-set tries to fix those two problems by allowing sharing sva >> domains with all devices bound to a mm. To achieve this, a new structure >> pointer is introduced to mm to replace the old PASID field, which can keep >> the info of PASID as well as the corresponding shared sva domains. >> Besides, function iommu_sva_bind_device() is updated to ensure a new sva >> domain can only be allocated when the old ones cannot work for the IOMMU. >> With these changes, a device driver can expect one sva domain could work >> for per PASID instance(e.g., enqcmd PASID instance), and therefore may get >> rid of handling sva domain duplication. Besides, IOMMU driver (e.g., intel >> vt-d driver) can get sufficient info (e.g., the info of the IOMMUs having >> their devices bound to one virtual address space) when handling >> mmu_notifier_ops callbacks, to remove the redundant IOTLB invalidations. >> >> Arguably there shouldn't be more than one sva_domain with the same PASID, >> and in any sane configuration there should be only 1 type of IOMMU driver >> that needs only 1 SVA domain. However, in reality, IOMMUs on one platform >> may not be identical to each other. Thus, attaching a sva domain that has >> been successfully bound to device A behind a IOMMU A, to device B behind >> IOMMU B may get failed due to the difference between IOMMU A and IOMMU >> B. In this case, a new sva domain with the same PASID needs to be >> allocated to work with IOMMU B. That's why we need a list to keep sva >> domains of one PASID. For the platform where IOMMUs are compatible to each >> other, there should be one sva domain in the list. >> >> v8: >> - CC more people >> - CCiommu@lists.linux.dev mailing list. >> When sending version 7, some issue happened in my CC list and that caused >> version 7 wasn't sent toiommu@lists.linux.dev. >> - Rebase to v6.6-rc6 and make a few format changes. > You should based it on Joerg's tree so he can take it without > conflcits. > > The conflicts are trivial though (Take Michael's version and switch > mm->pasid with mm_get_enqcmd_pasid(mm)) > > It looks fine, please lets get it in this cycle, the ARM and AMD SVA > series depend on it.
The vt-d driver also has series depending on it.
https://lore.kernel.org/linux-iommu/20231017032045.114868-1-tina.zhang@intel.com/
Best regards, baolu
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