Let's use alloc_contig_pages() for allocating memory and remove the linear mapping manually via arch_remove_linear_mapping(). Mark all pages PG_offline, such that they will definitely not get touched - e.g., when hibernating. When freeing memory, try to revert what we did. The original idea was discussed in: https://lkml.kernel.org/r/48340e96-7e6b-736f-9e23-d3111b915b6e@xxxxxxxxxx This is similar to CONFIG_DEBUG_PAGEALLOC handling on other architectures, whereby only single pages are unmapped from the linear mapping. Let's mimic what memory hot(un)plug would do with the linear mapping. We now need MEMORY_HOTPLUG and CONTIG_ALLOC as dependencies. Add a TODO that we want to use __GFP_ZERO for clearing once alloc_contig_pages() understands that. Tested with in QEMU/TCG with 10 GiB of main memory: [root@localhost ~]# echo 0x40000000 > /sys/kernel/debug/powerpc/memtrace/enable [ 105.903043][ T1080] memtrace: Allocated trace memory on node 0 at 0x0000000080000000 [root@localhost ~]# echo 0x40000000 > /sys/kernel/debug/powerpc/memtrace/enable [ 145.042493][ T1080] radix-mmu: Mapped 0x0000000080000000-0x00000000c0000000 with 64.0 KiB pages [ 145.049019][ T1080] memtrace: Freed trace memory back on node 0 [ 145.333960][ T1080] memtrace: Allocated trace memory on node 0 at 0x0000000080000000 [root@localhost ~]# echo 0x80000000 > /sys/kernel/debug/powerpc/memtrace/enable [ 213.606916][ T1080] radix-mmu: Mapped 0x0000000080000000-0x00000000c0000000 with 64.0 KiB pages [ 213.613855][ T1080] memtrace: Freed trace memory back on node 0 [ 214.185094][ T1080] memtrace: Allocated trace memory on node 0 at 0x0000000080000000 [root@localhost ~]# echo 0x100000000 > /sys/kernel/debug/powerpc/memtrace/enable [ 234.874872][ T1080] radix-mmu: Mapped 0x0000000080000000-0x0000000100000000 with 64.0 KiB pages [ 234.886974][ T1080] memtrace: Freed trace memory back on node 0 [ 234.890153][ T1080] memtrace: Failed to allocate trace memory on node 0 [root@localhost ~]# echo 0x40000000 > /sys/kernel/debug/powerpc/memtrace/enable [ 259.490196][ T1080] memtrace: Allocated trace memory on node 0 at 0x0000000080000000 I also made sure allocated memory is properly zeroed. Note 1: We currently won't be allocating from ZONE_MOVABLE - because our pages are not movable. However, as we don't run with any memory hot(un)plug mechanism around, we could make an exception to increase the chance of allocations succeeding. Note 2: PG_reserved isn't sufficient. E.g., kernel_page_present() used along PG_reserved in hibernation code will always return "true" on powerpc, resulting in the pages getting touched. It's too generic - e.g., indicates boot allocations. Note 3: For now, we keep using memory_block_size_bytes() as minimum granularity. Suggested-by: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx> Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx> Cc: Paul Mackerras <paulus@xxxxxxxxx> Cc: Rashmica Gupta <rashmica.g@xxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxx> Cc: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> --- arch/powerpc/platforms/powernv/Kconfig | 8 +- arch/powerpc/platforms/powernv/memtrace.c | 163 ++++++++-------------- 2 files changed, 62 insertions(+), 109 deletions(-) diff --git a/arch/powerpc/platforms/powernv/Kconfig b/arch/powerpc/platforms/powernv/Kconfig index 938803eab0ad..619b093a0657 100644 --- a/arch/powerpc/platforms/powernv/Kconfig +++ b/arch/powerpc/platforms/powernv/Kconfig @@ -27,11 +27,11 @@ config OPAL_PRD recovery diagnostics on OpenPower machines config PPC_MEMTRACE - bool "Enable removal of RAM from kernel mappings for tracing" - depends on PPC_POWERNV && MEMORY_HOTREMOVE + bool "Enable runtime allocation of RAM for tracing" + depends on PPC_POWERNV && MEMORY_HOTPLUG && CONTIG_ALLOC help - Enabling this option allows for the removal of memory (RAM) - from the kernel mappings to be used for hardware tracing. + Enabling this option allows for runtime allocation of memory (RAM) + for hardware tracing. config PPC_VAS bool "IBM Virtual Accelerator Switchboard (VAS)" diff --git a/arch/powerpc/platforms/powernv/memtrace.c b/arch/powerpc/platforms/powernv/memtrace.c index 0e42fe2d7b6a..5fc9408bb0b3 100644 --- a/arch/powerpc/platforms/powernv/memtrace.c +++ b/arch/powerpc/platforms/powernv/memtrace.c @@ -51,33 +51,12 @@ static const struct file_operations memtrace_fops = { .open = simple_open, }; -static int check_memblock_online(struct memory_block *mem, void *arg) -{ - if (mem->state != MEM_ONLINE) - return -1; - - return 0; -} - -static int change_memblock_state(struct memory_block *mem, void *arg) -{ - unsigned long state = (unsigned long)arg; - - mem->state = state; - - return 0; -} - static void memtrace_clear_range(unsigned long start_pfn, unsigned long nr_pages) { unsigned long pfn; - /* - * As pages are offline, we cannot trust the memmap anymore. As HIGHMEM - * does not apply, avoid passing around "struct page" and use - * clear_page() instead directly. - */ + /* As HIGHMEM does not apply, use clear_page() directly. */ for (pfn = start_pfn; pfn < start_pfn + nr_pages; pfn++) { if (IS_ALIGNED(pfn, PAGES_PER_SECTION)) cond_resched(); @@ -85,72 +64,39 @@ static void memtrace_clear_range(unsigned long start_pfn, } } -/* called with device_hotplug_lock held */ -static bool memtrace_offline_pages(u32 nid, u64 start_pfn, u64 nr_pages) -{ - const unsigned long start = PFN_PHYS(start_pfn); - const unsigned long size = PFN_PHYS(nr_pages); - - if (walk_memory_blocks(start, size, NULL, check_memblock_online)) - return false; - - walk_memory_blocks(start, size, (void *)MEM_GOING_OFFLINE, - change_memblock_state); - - if (offline_pages(start_pfn, nr_pages)) { - walk_memory_blocks(start, size, (void *)MEM_ONLINE, - change_memblock_state); - return false; - } - - walk_memory_blocks(start, size, (void *)MEM_OFFLINE, - change_memblock_state); - - - return true; -} - static u64 memtrace_alloc_node(u32 nid, u64 size) { - u64 start_pfn, end_pfn, nr_pages, pfn; - u64 base_pfn; - u64 bytes = memory_block_size_bytes(); + const unsigned long nr_pages = PHYS_PFN(size); + unsigned long pfn, start_pfn; + struct page *page; - if (!node_spanned_pages(nid)) + /* + * Trace memory needs to be aligned to the size, which is guaranteed + * by alloc_contig_pages(). + */ + page = alloc_contig_pages(nr_pages, GFP_KERNEL | __GFP_THISNODE | + __GFP_NOWARN, nid, NULL); + if (!page) return 0; + start_pfn = page_to_pfn(page); - start_pfn = node_start_pfn(nid); - end_pfn = node_end_pfn(nid); - nr_pages = size >> PAGE_SHIFT; - - /* Trace memory needs to be aligned to the size */ - end_pfn = round_down(end_pfn - nr_pages, nr_pages); - - lock_device_hotplug(); - for (base_pfn = end_pfn; base_pfn > start_pfn; base_pfn -= nr_pages) { - if (memtrace_offline_pages(nid, base_pfn, nr_pages) == true) { - /* - * Clear the range while we still have a linear - * mapping. - */ - memtrace_clear_range(base_pfn, nr_pages); - /* - * Remove memory in memory block size chunks so that - * iomem resources are always split to the same size and - * we never try to remove memory that spans two iomem - * resources. - */ - end_pfn = base_pfn + nr_pages; - for (pfn = base_pfn; pfn < end_pfn; pfn += bytes>> PAGE_SHIFT) { - __remove_memory(nid, pfn << PAGE_SHIFT, bytes); - } - unlock_device_hotplug(); - return base_pfn << PAGE_SHIFT; - } - } - unlock_device_hotplug(); + /* + * Clear the range while we still have a linear mapping. + * + * TODO: use __GFP_ZERO with alloc_contig_pages() once supported. + */ + memtrace_clear_range(start_pfn, nr_pages); - return 0; + /* + * Set pages PageOffline(), to indicate that nobody (e.g., hibernation, + * dumping, ...) should be touching these pages. + */ + for (pfn = start_pfn; pfn < start_pfn + nr_pages; pfn++) + __SetPageOffline(pfn_to_page(pfn)); + + arch_remove_linear_mapping(PFN_PHYS(start_pfn), size); + + return PFN_PHYS(start_pfn); } static int memtrace_init_regions_runtime(u64 size) @@ -220,16 +166,30 @@ static int memtrace_init_debugfs(void) return ret; } -static int online_mem_block(struct memory_block *mem, void *arg) +static int memtrace_free(int nid, u64 start, u64 size) { - return device_online(&mem->dev); + struct mhp_params params = { .pgprot = PAGE_KERNEL }; + const unsigned long nr_pages = PHYS_PFN(size); + const unsigned long start_pfn = PHYS_PFN(start); + unsigned long pfn; + int ret; + + ret = arch_create_linear_mapping(nid, start, size, ¶ms); + if (ret) + return ret; + + for (pfn = start_pfn; pfn < start_pfn + nr_pages; pfn++) + __ClearPageOffline(pfn_to_page(pfn)); + + free_contig_range(start_pfn, nr_pages); + return 0; } /* - * Iterate through the chunks of memory we have removed from the kernel - * and attempt to add them back to the kernel. + * Iterate through the chunks of memory we allocated and attempt to expose + * them back to the kernel. */ -static int memtrace_online(void) +static int memtrace_free_regions(void) { int i, ret = 0; struct memtrace_entry *ent; @@ -237,7 +197,7 @@ static int memtrace_online(void) for (i = memtrace_array_nr - 1; i >= 0; i--) { ent = &memtrace_array[i]; - /* We have onlined this chunk previously */ + /* We have freed this chunk previously */ if (ent->nid == NUMA_NO_NODE) continue; @@ -247,30 +207,25 @@ static int memtrace_online(void) ent->mem = 0; } - if (add_memory(ent->nid, ent->start, ent->size, MHP_NONE)) { - pr_err("Failed to add trace memory to node %d\n", + if (memtrace_free(ent->nid, ent->start, ent->size)) { + pr_err("Failed to free trace memory on node %d\n", ent->nid); ret += 1; continue; } - lock_device_hotplug(); - walk_memory_blocks(ent->start, ent->size, NULL, - online_mem_block); - unlock_device_hotplug(); - /* - * Memory was added successfully so clean up references to it - * so on reentry we can tell that this chunk was added. + * Memory was freed successfully so clean up references to it + * so on reentry we can tell that this chunk was freed. */ debugfs_remove_recursive(ent->dir); - pr_info("Added trace memory back to node %d\n", ent->nid); + pr_info("Freed trace memory back on node %d\n", ent->nid); ent->size = ent->start = ent->nid = NUMA_NO_NODE; } if (ret) return ret; - /* If all chunks of memory were added successfully, reset globals */ + /* If all chunks of memory were freed successfully, reset globals */ kfree(memtrace_array); memtrace_array = NULL; memtrace_size = 0; @@ -295,18 +250,16 @@ static int memtrace_enable_set(void *data, u64 val) mutex_lock(&memtrace_mutex); - /* Re-add/online previously removed/offlined memory */ - if (memtrace_size) { - if (memtrace_online()) - goto out_unlock; - } + /* Free all previously allocated memory. */ + if (memtrace_size && memtrace_free_regions()) + goto out_unlock; if (!val) { rc = 0; goto out_unlock; } - /* Offline and remove memory */ + /* Allocate memory. */ if (memtrace_init_regions_runtime(val)) goto out_unlock; -- 2.26.2
