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Mon, 19 Oct 2020 19:15:31 +0000 Subject: Re: [PATCH v26 13/17] vfio: create mapped iova list when vIOMMU is enabled To: Alex Williamson References: <1600817059-26721-1-git-send-email-kwankhede@nvidia.com> <1600817059-26721-14-git-send-email-kwankhede@nvidia.com> <20200925162316.53dbd2b0@x1.home> <20201019112408.470ae1e8@w520.home> X-Nvconfidentiality: public From: Kirti Wankhede Message-ID: <52361a71-f812-5f69-be57-93b732e96ed1@nvidia.com> Date: Tue, 20 Oct 2020 00:45:28 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <20201019112408.470ae1e8@w520.home> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To HQMAIL107.nvidia.com (172.20.187.13) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1603134899; bh=5WFxs9VoCbgx1LkGMyfXvlpNSZQhis5e8skeiC/lqhI=; 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For each mapped iova >>>> save translated address. Add node to list on MAP and remove node from >>>> list on UNMAP. >>>> This list is used to track dirty pages during migration. >>>> >>>> Signed-off-by: Kirti Wankhede >>>> --- >>>> hw/vfio/common.c | 58 ++++++++++++++++++++++++++++++++++++++----- >>>> include/hw/vfio/vfio-common.h | 8 ++++++ >>>> 2 files changed, 60 insertions(+), 6 deletions(-) >>>> >>>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c >>>> index d4959c036dd1..dc56cded2d95 100644 >>>> --- a/hw/vfio/common.c >>>> +++ b/hw/vfio/common.c >>>> @@ -407,8 +407,8 @@ static bool vfio_listener_skipped_section(MemoryRegionSection *section) >>>> } >>>> >>>> /* Called with rcu_read_lock held. */ >>>> -static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb, void **vaddr, >>>> - bool *read_only) >>>> +static bool vfio_get_xlat_addr(IOMMUTLBEntry *iotlb, void **vaddr, >>>> + ram_addr_t *ram_addr, bool *read_only) >>>> { >>>> MemoryRegion *mr; >>>> hwaddr xlat; >>>> @@ -439,8 +439,17 @@ static bool vfio_get_vaddr(IOMMUTLBEntry *iotlb, void **vaddr, >>>> return false; >>>> } >>>> >>>> - *vaddr = memory_region_get_ram_ptr(mr) + xlat; >>>> - *read_only = !writable || mr->readonly; >>>> + if (vaddr) { >>>> + *vaddr = memory_region_get_ram_ptr(mr) + xlat; >>>> + } >>>> + >>>> + if (ram_addr) { >>>> + *ram_addr = memory_region_get_ram_addr(mr) + xlat; >>>> + } >>>> + >>>> + if (read_only) { >>>> + *read_only = !writable || mr->readonly; >>>> + } >>>> >>>> return true; >>>> } >>>> @@ -450,7 +459,6 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb) >>>> VFIOGuestIOMMU *giommu = container_of(n, VFIOGuestIOMMU, n); >>>> VFIOContainer *container = giommu->container; >>>> hwaddr iova = iotlb->iova + giommu->iommu_offset; >>>> - bool read_only; >>>> void *vaddr; >>>> int ret; >>>> >>>> @@ -466,7 +474,10 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb) >>>> rcu_read_lock(); >>>> >>>> if ((iotlb->perm & IOMMU_RW) != IOMMU_NONE) { >>>> - if (!vfio_get_vaddr(iotlb, &vaddr, &read_only)) { >>>> + ram_addr_t ram_addr; >>>> + bool read_only; >>>> + >>>> + if (!vfio_get_xlat_addr(iotlb, &vaddr, &ram_addr, &read_only)) { >>>> goto out; >>>> } >>>> /* >>>> @@ -484,8 +495,28 @@ static void vfio_iommu_map_notify(IOMMUNotifier *n, IOMMUTLBEntry *iotlb) >>>> "0x%"HWADDR_PRIx", %p) = %d (%m)", >>>> container, iova, >>>> iotlb->addr_mask + 1, vaddr, ret); >>>> + } else { >>>> + VFIOIovaRange *iova_range; >>>> + >>>> + iova_range = g_malloc0(sizeof(*iova_range)); >>>> + iova_range->iova = iova; >>>> + iova_range->size = iotlb->addr_mask + 1; >>>> + iova_range->ram_addr = ram_addr; >>>> + >>>> + QLIST_INSERT_HEAD(&giommu->iova_list, iova_range, next); >>>> } >>>> } else { >>>> + VFIOIovaRange *iova_range, *tmp; >>>> + >>>> + QLIST_FOREACH_SAFE(iova_range, &giommu->iova_list, next, tmp) { >>>> + if (iova_range->iova >= iova && >>>> + iova_range->iova + iova_range->size <= iova + >>>> + iotlb->addr_mask + 1) { >>>> + QLIST_REMOVE(iova_range, next); >>>> + g_free(iova_range); >>>> + } >>>> + } >>>> + >>> >>> >>> This is some pretty serious overhead... can't we trigger a replay when >>> migration is enabled to build this information then? >> >> Are you suggesting to call memory_region_iommu_replay() before >> vfio_sync_dirty_bitmap(), which would call vfio_iommu_map_notify() where >> iova list of mapping is maintained? Then in the notifer check if >> migration_is_running() and container->dirty_pages_supported == true, >> then only create iova mapping tree? In this case how would we know that >> this is triggered by >> vfio_sync_dirty_bitmap() >> -> memory_region_iommu_replay() >> and we don't have to call vfio_dma_map()? > > memory_region_iommu_replay() calls a notifier of our choice, so we > could create a notifier specifically for creating this tree when dirty > logging is enabled. Thanks, > This would also mean changes in intel_iommu.c such that it would walk through the iova_tree and call notifier for each entry in iova_tree. What about other platforms? We will have to handle such cases for AMD, ARM, PPC etc...? I don't see replay callback for AMD, that would result in minimum IOMMU supported page size granularity walk - which is similar to that I tried to implement 2-3 versions back. Does that mean doing such change would improve performance for Intel IOMMU but worsen for AMD/PPC? I'm changing list to tree as first level of improvement in this patch. Can we do the change you suggested above later as next level of improvement? Thanks, Kirti