The patch titled Subject: mm/vmemmap/devdax: fix kernel crash when probing devdax devices has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-vmemmap-devdax-fix-kernel-crash-when-probing-devdax-devices.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: "Aneesh Kumar K.V" aneesh.kumar@linux.ibm.com Subject: mm/vmemmap/devdax: fix kernel crash when probing devdax devices Date: Fri, 7 Apr 2023 17:53:53 +0530

commit c4386bd8ee3a ("mm/memremap: add ZONE_DEVICE support for compound pages") added support for using optimized vmmemap for devdax devices. But how vmemmap mappings are created are architecture specific. For example, powerpc with hash translation doesn't have vmemmap mappings in init_mm page table instead they are bolted table entries in the hardware page table

vmemmap_populate_compound_pages() used by vmemmap optimization code is not aware of these architecture-specific mapping. Hence allow architecture to opt for this feature. I selected architectures supporting HUGETLB_PAGE_OPTIMIZE_VMEMMAP option as also supporting this feature. I added vmemmap_can_optimize() even though page_vmemmap_nr(pgmap) > 1 check should filter architecture not supporting this. IMHO that brings clarity to the code where we are populating vmemmap.

This patch fixes the below crash on ppc64.

BUG: Unable to handle kernel data access on write at 0xc00c000100400038 Faulting instruction address: 0xc000000001269d90 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries Modules linked in: CPU: 7 PID: 1 Comm: swapper/0 Not tainted 6.3.0-rc5-150500.34-default+ #2 5c90a668b6bbd142599890245c2fb5de19d7d28a Hardware name: IBM,9009-42G POWER9 (raw) 0x4e0202 0xf000005 of:IBM,FW950.40 (VL950_099) hv:phyp pSeries NIP: c000000001269d90 LR: c0000000004c57d4 CTR: 0000000000000000 REGS: c000000003632c30 TRAP: 0300 Not tainted (6.3.0-rc5-150500.34-default+) MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 24842228 XER: 00000000 CFAR: c0000000004c57d0 DAR: c00c000100400038 DSISR: 42000000 IRQMASK: 0 .... NIP [c000000001269d90] __init_single_page.isra.74+0x14/0x4c LR [c0000000004c57d4] __init_zone_device_page+0x44/0xd0 Call Trace: [c000000003632ed0] [c000000003632f60] 0xc000000003632f60 (unreliable) [c000000003632f10] [c0000000004c5ca0] memmap_init_zone_device+0x170/0x250 [c000000003632fe0] [c0000000005575f8] memremap_pages+0x2c8/0x7f0 [c0000000036330c0] [c000000000557b5c] devm_memremap_pages+0x3c/0xa0 [c000000003633100] [c000000000d458a8] dev_dax_probe+0x108/0x3e0 [c0000000036331a0] [c000000000d41430] dax_bus_probe+0xb0/0x140 [c0000000036331d0] [c000000000cef27c] really_probe+0x19c/0x520 [c000000003633260] [c000000000cef6b4] __driver_probe_device+0xb4/0x230 [c0000000036332e0] [c000000000cef888] driver_probe_device+0x58/0x120 [c000000003633320] [c000000000cefa6c] __device_attach_driver+0x11c/0x1e0 [c0000000036333a0] [c000000000cebc58] bus_for_each_drv+0xa8/0x130 [c000000003633400] [c000000000ceefcc] __device_attach+0x15c/0x250 [c0000000036334a0] [c000000000ced458] bus_probe_device+0x108/0x110 [c0000000036334f0] [c000000000ce92dc] device_add+0x7fc/0xa10 [c0000000036335b0] [c000000000d447c8] devm_create_dev_dax+0x1d8/0x530 [c000000003633640] [c000000000d46b60] __dax_pmem_probe+0x200/0x270 [c0000000036337b0] [c000000000d46bf0] dax_pmem_probe+0x20/0x70 [c0000000036337d0] [c000000000d2279c] nvdimm_bus_probe+0xac/0x2b0 [c000000003633860] [c000000000cef27c] really_probe+0x19c/0x520 [c0000000036338f0] [c000000000cef6b4] __driver_probe_device+0xb4/0x230 [c000000003633970] [c000000000cef888] driver_probe_device+0x58/0x120 [c0000000036339b0] [c000000000cefd08] __driver_attach+0x1d8/0x240 [c000000003633a30] [c000000000cebb04] bus_for_each_dev+0xb4/0x130 [c000000003633a90] [c000000000cee564] driver_attach+0x34/0x50 [c000000003633ab0] [c000000000ced878] bus_add_driver+0x218/0x300 [c000000003633b40] [c000000000cf1144] driver_register+0xa4/0x1b0 [c000000003633bb0] [c000000000d21a0c] __nd_driver_register+0x5c/0x100 [c000000003633c10] [c00000000206a2e8] dax_pmem_init+0x34/0x48 [c000000003633c30] [c0000000000132d0] do_one_initcall+0x60/0x320 [c000000003633d00] [c0000000020051b0] kernel_init_freeable+0x360/0x400 [c000000003633de0] [c000000000013764] kernel_init+0x34/0x1d0 [c000000003633e50] [c00000000000de14] ret_from_kernel_thread+0x5c/0x64

Link: https://lkml.kernel.org/r/20230407122353.12018-1-aneesh.kumar@linux.ibm.com Fixes: c4386bd8ee3a ("mm/memremap: add ZONE_DEVICE support for compound pages") Signed-off-by: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Reported-by: Tarun Sahu tsahu@linux.ibm.com Cc: Joao Martins joao.m.martins@oracle.com Cc: Muchun Song songmuchun@bytedance.com Cc: Dan Williams dan.j.williams@intel.com Cc: Jane Chu jane.chu@oracle.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

arch/arm64/Kconfig | 1 + arch/loongarch/Kconfig | 1 + arch/s390/Kconfig | 1 + arch/x86/Kconfig | 1 + drivers/dax/device.c | 3 ++- include/linux/mm.h | 16 ++++++++++++++++ mm/Kconfig | 3 +++ mm/sparse-vmemmap.c | 3 +-- 8 files changed, 26 insertions(+), 3 deletions(-)

--- a/arch/arm64/Kconfig~mm-vmemmap-devdax-fix-kernel-crash-when-probing-devdax-devices +++ a/arch/arm64/Kconfig @@ -102,6 +102,7 @@ config ARM64 select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36) select ARCH_WANT_LD_ORPHAN_WARN select ARCH_WANTS_NO_INSTR + select ARCH_WANT_OPTIMIZE_VMEMMAP select ARCH_WANTS_THP_SWAP if ARM64_4K_PAGES select ARCH_HAS_UBSAN_SANITIZE_ALL select ARM_AMBA --- a/arch/loongarch/Kconfig~mm-vmemmap-devdax-fix-kernel-crash-when-probing-devdax-devices +++ a/arch/loongarch/Kconfig @@ -56,6 +56,7 @@ config LOONGARCH select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP select ARCH_WANT_LD_ORPHAN_WARN select ARCH_WANTS_NO_INSTR + select ARCH_WANT_OPTIMIZE_VMEMMAP select BUILDTIME_TABLE_SORT select COMMON_CLK select CPU_PM --- a/arch/s390/Kconfig~mm-vmemmap-devdax-fix-kernel-crash-when-probing-devdax-devices +++ a/arch/s390/Kconfig @@ -127,6 +127,7 @@ config S390 select ARCH_WANT_DEFAULT_BPF_JIT select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP select ARCH_WANT_IPC_PARSE_VERSION + select ARCH_WANT_OPTIMIZE_VMEMMAP select BUILDTIME_TABLE_SORT select CLONE_BACKWARDS2 select DMA_OPS if PCI --- a/arch/x86/Kconfig~mm-vmemmap-devdax-fix-kernel-crash-when-probing-devdax-devices +++ a/arch/x86/Kconfig @@ -127,6 +127,7 @@ config X86 select ARCH_WANT_HUGE_PMD_SHARE select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP if X86_64 select ARCH_WANT_LD_ORPHAN_WARN + select ARCH_WANT_OPTIMIZE_VMEMMAP if X86_64 select ARCH_WANTS_THP_SWAP if X86_64 select ARCH_HAS_PARANOID_L1D_FLUSH select BUILDTIME_TABLE_SORT --- a/drivers/dax/device.c~mm-vmemmap-devdax-fix-kernel-crash-when-probing-devdax-devices +++ a/drivers/dax/device.c @@ -448,7 +448,8 @@ int dev_dax_probe(struct dev_dax *dev_da }

pgmap->type = MEMORY_DEVICE_GENERIC; - if (dev_dax->align > PAGE_SIZE) + if (dev_dax->align > PAGE_SIZE && + IS_ENABLED(CONFIG_ARCH_WANT_OPTIMIZE_VMEMMAP)) pgmap->vmemmap_shift = order_base_2(dev_dax->align >> PAGE_SHIFT); addr = devm_memremap_pages(dev, pgmap); --- a/include/linux/mm.h~mm-vmemmap-devdax-fix-kernel-crash-when-probing-devdax-devices +++ a/include/linux/mm.h @@ -3425,6 +3425,22 @@ void vmemmap_populate_print_last(void); void vmemmap_free(unsigned long start, unsigned long end, struct vmem_altmap *altmap); #endif + +#ifdef CONFIG_ARCH_WANT_OPTIMIZE_VMEMMAP +static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap, + struct dev_pagemap *pgmap) +{ + return is_power_of_2(sizeof(struct page)) && + pgmap && (pgmap_vmemmap_nr(pgmap) > 1) && !altmap; +} +#else +static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap, + struct dev_pagemap *pgmap) +{ + return false; +} +#endif + void register_page_bootmem_memmap(unsigned long section_nr, struct page *map, unsigned long nr_pages);

--- a/mm/Kconfig~mm-vmemmap-devdax-fix-kernel-crash-when-probing-devdax-devices +++ a/mm/Kconfig @@ -480,6 +480,9 @@ config SPARSEMEM_VMEMMAP pfn_to_page and page_to_pfn operations. This is the most efficient option when sufficient kernel resources are available.

+config ARCH_WANT_OPTIMIZE_VMEMMAP + bool + config HAVE_MEMBLOCK_PHYS_MAP bool

--- a/mm/sparse-vmemmap.c~mm-vmemmap-devdax-fix-kernel-crash-when-probing-devdax-devices +++ a/mm/sparse-vmemmap.c @@ -458,8 +458,7 @@ struct page * __meminit __populate_secti !IS_ALIGNED(nr_pages, PAGES_PER_SUBSECTION))) return NULL;

- if (is_power_of_2(sizeof(struct page)) && - pgmap && pgmap_vmemmap_nr(pgmap) > 1 && !altmap) + if (vmemmap_can_optimize(altmap, pgmap)) r = vmemmap_populate_compound_pages(pfn, start, end, nid, pgmap); else r = vmemmap_populate(start, end, nid, altmap); _

Patches currently in -mm which might be from aneesh.kumar@linux.ibm.com are

mm-vmemmap-devdax-fix-kernel-crash-when-probing-devdax-devices.patch