On Thu, 30 Nov 2023, Pasha Tatashin wrote: > IOMMU subsystem may contain state that is in gigabytes. Majority of that > state is iommu page tables. Yet, there is currently, no way to observe > how much memory is actually used by the iommu subsystem. > > This patch series solves this problem by adding both observability to > all pages that are allocated by IOMMU, and also accountability, so > admins can limit the amount if via cgroups. > > The system-wide observability is using /proc/meminfo: > SecPageTables: 438176 kB > > Contains IOMMU and KVM memory. > > Per-node observability: > /sys/devices/system/node/nodeN/meminfo > Node N SecPageTables: 422204 kB > > Contains IOMMU and KVM memory memory in the given NUMA node. > > Per-node IOMMU only observability: > /sys/devices/system/node/nodeN/vmstat > nr_iommu_pages 105555 > > Contains number of pages IOMMU allocated in the given node. > > Accountability: using sec_pagetables cgroup-v2 memory.stat entry. > > With the change, iova_stress[1] stops as limit is reached: > > # ./iova_stress > iova space: 0T free memory: 497G > iova space: 1T free memory: 495G > iova space: 2T free memory: 493G > iova space: 3T free memory: 491G > > stops as limit is reached. > I think this is *very* useful to provide visibility into a significant amount of memory that we currently cannot observe on a host. It can help to uncover bugs and shed light onto a particularly large amount of memory that would otherwise be mysterious. Joerg, Will, Robin, I think this series would go through the git://git.kernel.org/pub/scm/linux/kernel/git/joro/iommu.git tree since it depends on a common framework for all other IOMMU implementations to then use? Any concerns about this patch series? It would be very useful for us to create visibility into this memory. Pasha: any chance of adding a selftest that can be run that will test the value of nr_iommu_pages? I could imagine in the future that a bug could be introduced where either an allocation or free is done through alloc_pages() directly and its paired alloc/free function now results in a leak or underflow. > This series encorporates suggestions that came from the discussion > at LPC [2]. > ---------------------------------------------------------------------- > [1] https://github.com/soleen/iova_stress > [2] https://lpc.events/event/17/contributions/1466 > ---------------------------------------------------------------------- > Previous versions > v1: https://lore.kernel.org/all/20231128204938.1453583-1-pasha.tatashin@xxxxxxxxxx > ---------------------------------------------------------------------- > > Pasha Tatashin (10): > iommu/vt-d: add wrapper functions for page allocations > iommu/amd: use page allocation function provided by iommu-pages.h > iommu/io-pgtable-arm: use page allocation function provided by > iommu-pages.h > iommu/io-pgtable-dart: use page allocation function provided by > iommu-pages.h > iommu/exynos: use page allocation function provided by iommu-pages.h > iommu/rockchip: use page allocation function provided by iommu-pages.h > iommu/sun50i: use page allocation function provided by iommu-pages.h > iommu/tegra-smmu: use page allocation function provided by > iommu-pages.h > iommu: observability of the IOMMU allocations > iommu: account IOMMU allocated memory > > Documentation/admin-guide/cgroup-v2.rst | 2 +- > Documentation/filesystems/proc.rst | 4 +- > drivers/iommu/amd/amd_iommu.h | 8 - > drivers/iommu/amd/init.c | 91 +++++----- > drivers/iommu/amd/io_pgtable.c | 13 +- > drivers/iommu/amd/io_pgtable_v2.c | 20 +- > drivers/iommu/amd/iommu.c | 13 +- > drivers/iommu/exynos-iommu.c | 14 +- > drivers/iommu/intel/dmar.c | 10 +- > drivers/iommu/intel/iommu.c | 47 ++--- > drivers/iommu/intel/iommu.h | 2 - > drivers/iommu/intel/irq_remapping.c | 10 +- > drivers/iommu/intel/pasid.c | 12 +- > drivers/iommu/intel/svm.c | 7 +- > drivers/iommu/io-pgtable-arm.c | 7 +- > drivers/iommu/io-pgtable-dart.c | 37 ++-- > drivers/iommu/iommu-pages.h | 231 ++++++++++++++++++++++++ > drivers/iommu/rockchip-iommu.c | 14 +- > drivers/iommu/sun50i-iommu.c | 7 +- > drivers/iommu/tegra-smmu.c | 18 +- > include/linux/mmzone.h | 5 +- > mm/vmstat.c | 3 + > 22 files changed, 390 insertions(+), 185 deletions(-) > create mode 100644 drivers/iommu/iommu-pages.h > > -- > 2.43.0.rc2.451.g8631bc7472-goog > > >
