Hi, On 9/1/21 8:33 AM, Liu, Renwei wrote: >> -----Original Message----- >> From: Eric Auger [mailto:eric.au...@redhat.com] >> Sent: Tuesday, August 31, 2021 10:46 PM >> To: Liu, Renwei; Peter Maydell >> Cc: qemu-...@nongnu.org; qemu-devel@nongnu.org; Li, Chunming; Wen, >> Jianxian >> Subject: Re: [PATCH v2] hw/arm/smmuv3: Simplify range invalidation >> >> Hi Liu, >> >> On 8/23/21 9:50 AM, Liu, Renwei wrote: >>> Simplify range invalidation which can avoid to iterate over all >>> iotlb entries multi-times. For instance invalidations patterns like >>> "invalidate 32 4kB pages starting from 0xffacd000" need to iterate >> over >>> all iotlb entries 6 times (num_pages: 1, 2, 16, 8, 4, 1). It only >> needs >>> to iterate over all iotlb entries once with new implementation. >> This wouldn't work. This reverts commit >> 6d9cd115b9df ("hw/arm/smmuv3: Enforce invalidation on a power of two >> range") >> which is mandated for VFIO and virtio to work. IOTLB invalidations must >> be naturally aligned and with a power of 2 range, hence this iteration. >> >> Thanks >> >> Eric > Hi Eric, > > Could you try the patch firstly? I want to know whether it's failed > in your application scenario with this implementation. There are many test cases, virtio-pci, vhost, VFIO, ... > I agree with you that IOTLB entry must be naturally aligned and > with a power of 2 range. But we can invalidate multi IOTLB entries > in one iteration. We check the overlap between invalidation range > and IOTLB range, not check mask. This smmu_hash_remove_by_asid_iova() change only affects the internal SMMUv3 IOTLB hash table lookup. However there are also IOTLB invalidation notifications sent to components who registered notifiers, ie. smmuv3_notify_iova path. > The final result is same with > your implementation (split to multi times with a power of 2 range). > I wonder why we can't implement it directly when the application can > send an invalidation command with a non power of 2 range. > We have tested it in our application scenario and not find any fail. Assume the driver invalidates 5 * 4kB pages =0x5000 range. Without the loop you removed
in smmuv3_notify_iova() event.entry.addr_mask = num_pages * (1 << granule) - 1 = 0x4FFF. This addr_mask is an invalid mask this entry is passed to components who registered invalidation notifiers such as vhost or vfio. for instance in VFIO you have '&' ops on the addr_mask. addr_mask is expected to be a mask of a power of 2 range. Does it clarify? Thanks Eric > > In addition, from the code implementation, smmu_iotlb_inv_iova() > should be OK. In another call smmuv3_inv_notifiers_iova() -> > smmuv3_notify_iova() -> memory_region_notify_iommu_one(), > it also checks range overlap. So it should be OK if the range > is not a power of 2. > > Could you take a look at it again? > > Thanks > Renwei Liu
