From: Ankit Agrawal <ankita@xxxxxxxxxx> The kernel MM currently handles ECC errors / poison only on memory page backed by struct page. As part of [1], the nvgrace-gpu-vfio-pci module maps the device memory to user VA (Qemu) using remap_pfn_range without being added to the kernel. These pages are not backed by struct page. Implement a new ECC handling for memory without struct pages. Kernel MM expose registration APIs to allow modules that are managing the device to register its memory region and a callback function. MM then tracks such regions using interval tree. The mechanism is largely similar to that of ECC on pfn with struct pages. If there is an ECC error on a pfn, MM uses the registered memory failure callback function to notify the module of the faulty PFN, so that the module may take any required action. The pfn is then unmapped in Stage-2. When the VM tries to access the page, it gets trapped in KVM, which calls the vm ops fault function. If the module fault function returns VM_FAULT_HWPOISON, KVM sends a BUS_MCEERR_AR to the usermode (Qemu) mapped to the poisoned page. Lastly, nvgrace-gpu-vfio-pci module make use of the new mechanism to get poison handling support on the device memory. Patch generated over v6.6-rc2 and with [1] applied. [1] is currently under review. [1] https://lore.kernel.org/all/20230915025415.6762-1-ankita@xxxxxxxxxx/ Ankit Agrawal (4): mm: handle poisoning of pfn without struct pages mm: Add poison error check in fixup_user_fault() for mapped pfn mm: Change ghes code to allow poison of non-struct pfn vfio/nvgpu: register device memory for poison handling drivers/acpi/apei/ghes.c | 12 +-- drivers/vfio/pci/nvgrace-gpu/main.c | 107 +++++++++++++++++++++- drivers/vfio/vfio.h | 11 --- drivers/vfio/vfio_main.c | 3 +- include/linux/memory-failure.h | 22 +++++ include/linux/mm.h | 1 + include/linux/vfio.h | 15 ++++ include/ras/ras_event.h | 1 + mm/Kconfig | 1 + mm/gup.c | 2 +- mm/memory-failure.c | 135 +++++++++++++++++++++++----- virt/kvm/kvm_main.c | 6 ++ 12 files changed, 270 insertions(+), 46 deletions(-) create mode 100644 include/linux/memory-failure.h -- 2.17.1
