On Tue, 01 Aug 2023 23:55:37 -0600 Vishal Verma <[email protected]> wrote:
> The MHP_MEMMAP_ON_MEMORY flag for hotplugged memory is restricted to > 'memblock_size' chunks of memory being added. Adding a larger span of > memory precludes memmap_on_memory semantics. > > For users of hotplug such as kmem, large amounts of memory might get > added from the CXL subsystem. In some cases, this amount may exceed the > available 'main memory' to store the memmap for the memory being added. > In this case, it is useful to have a way to place the memmap on the > memory being added, even if it means splitting the addition into > memblock-sized chunks. > > Change add_memory_resource() to loop over memblock-sized chunks of > memory if caller requested memmap_on_memory, and if other conditions for > it are met. Teach try_remove_memory() to also expect that a memory > range being removed might have been split up into memblock sized chunks, > and to loop through those as needed. > > Cc: Andrew Morton <[email protected]> > Cc: David Hildenbrand <[email protected]> > Cc: Michal Hocko <[email protected]> > Cc: Oscar Salvador <[email protected]> > Cc: Dan Williams <[email protected]> > Cc: Dave Jiang <[email protected]> > Cc: Dave Hansen <[email protected]> > Cc: Huang Ying <[email protected]> > Suggested-by: David Hildenbrand <[email protected]> > Signed-off-by: Vishal Verma <[email protected]> A couple of trivial comments inline. > --- > mm/memory_hotplug.c | 150 > ++++++++++++++++++++++++++++++++-------------------- > 1 file changed, 93 insertions(+), 57 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index d282664f558e..cae03c8d4bbf 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1383,6 +1383,44 @@ static bool mhp_supports_memmap_on_memory(unsigned > long size) > return arch_supports_memmap_on_memory(vmemmap_size); > } > > +static int add_memory_create_devices(int nid, struct memory_group *group, > + u64 start, u64 size, mhp_t mhp_flags) > +{ > + struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; > + struct vmem_altmap mhp_altmap = { > + .base_pfn = PHYS_PFN(start), > + .end_pfn = PHYS_PFN(start + size - 1), > + }; > + int ret; > + > + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY)) { > + mhp_altmap.free = memory_block_memmap_on_memory_pages(); > + params.altmap = kmalloc(sizeof(struct vmem_altmap), GFP_KERNEL); > + if (!params.altmap) > + return -ENOMEM; > + > + memcpy(params.altmap, &mhp_altmap, sizeof(mhp_altmap)); > + } > + > + /* call arch's memory hotadd */ > + ret = arch_add_memory(nid, start, size, ¶ms); > + if (ret < 0) > + goto error; > + > + /* create memory block devices after memory was added */ > + ret = create_memory_block_devices(start, size, params.altmap, group); > + if (ret) { > + arch_remove_memory(start, size, NULL); Maybe push this down to a second label? > + goto error; > + } > + > + return 0; > + > +error: > + kfree(params.altmap); > + return ret; > +} > + > /* > * NOTE: The caller must call lock_device_hotplug() to serialize hotplug > * and online/offline operations (triggered e.g. by sysfs). > @@ -1391,14 +1429,10 @@ static bool mhp_supports_memmap_on_memory(unsigned > long size) > */ > int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) > { > - struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; > + unsigned long memblock_size = memory_block_size_bytes(); > enum memblock_flags memblock_flags = MEMBLOCK_NONE; > - struct vmem_altmap mhp_altmap = { > - .base_pfn = PHYS_PFN(res->start), > - .end_pfn = PHYS_PFN(res->end), > - }; > struct memory_group *group = NULL; > - u64 start, size; > + u64 start, size, cur_start; > bool new_node = false; > int ret; > > @@ -1439,28 +1473,21 @@ int __ref add_memory_resource(int nid, struct > resource *res, mhp_t mhp_flags) > /* > * Self hosted memmap array > */ > - if (mhp_flags & MHP_MEMMAP_ON_MEMORY) { > - if (mhp_supports_memmap_on_memory(size)) { > - mhp_altmap.free = memory_block_memmap_on_memory_pages(); > - params.altmap = kmalloc(sizeof(struct vmem_altmap), > GFP_KERNEL); > - if (!params.altmap) > + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY) && > + mhp_supports_memmap_on_memory(memblock_size)) { > + for (cur_start = start; cur_start < start + size; > + cur_start += memblock_size) { > + ret = add_memory_create_devices(nid, group, cur_start, > + memblock_size, > + mhp_flags); > + if (ret) > goto error; > - > - memcpy(params.altmap, &mhp_altmap, sizeof(mhp_altmap)); > } > - /* fallback to not using altmap */ > - } > - > - /* call arch's memory hotadd */ > - ret = arch_add_memory(nid, start, size, ¶ms); > - if (ret < 0) > - goto error_free; > - > - /* create memory block devices after memory was added */ > - ret = create_memory_block_devices(start, size, params.altmap, group); > - if (ret) { > - arch_remove_memory(start, size, NULL); > - goto error_free; > + } else { > + ret = add_memory_create_devices(nid, group, start, size, > + mhp_flags); > + if (ret) > + goto error; > } > > if (new_node) { > @@ -1497,8 +1524,6 @@ int __ref add_memory_resource(int nid, struct resource > *res, mhp_t mhp_flags) > walk_memory_blocks(start, size, NULL, online_memory_block); > > return ret; > -error_free: > - kfree(params.altmap); > error: > if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) > memblock_remove(start, size); > @@ -2149,40 +2174,14 @@ void try_offline_node(int nid) > } > EXPORT_SYMBOL(try_offline_node); > > -static int __ref try_remove_memory(u64 start, u64 size) > +static void __ref __try_remove_memory(int nid, u64 start, u64 size) > { > - int ret; > - struct memory_block *mem; > - int rc = 0, nid = NUMA_NO_NODE; > struct vmem_altmap *altmap = NULL; > + struct memory_block *mem; > + int ret; > > - BUG_ON(check_hotplug_memory_range(start, size)); > - > - /* > - * All memory blocks must be offlined before removing memory. Check > - * whether all memory blocks in question are offline and return error > - * if this is not the case. > - * > - * While at it, determine the nid. Note that if we'd have mixed nodes, > - * we'd only try to offline the last determined one -- which is good > - * enough for the cases we care about. > - */ > - rc = walk_memory_blocks(start, size, &nid, check_memblock_offlined_cb); > - if (rc) > - return rc; > - > - /* > - * We only support removing memory added with MHP_MEMMAP_ON_MEMORY in > - * the same granularity it was added - a single memory block. > - */ > ret = walk_memory_blocks(start, size, &mem, test_has_altmap_cb); > if (ret) { > - if (size != memory_block_size_bytes()) { > - pr_warn("Refuse to remove %#llx - %#llx," > - "wrong granularity\n", > - start, start + size); > - return -EINVAL; > - } > altmap = mem->altmap; > /* > * Mark altmap NULL so that we can add a debug > @@ -2221,6 +2220,43 @@ static int __ref try_remove_memory(u64 start, u64 size) > try_offline_node(nid); > > mem_hotplug_done(); > +} > + > +static int __ref try_remove_memory(u64 start, u64 size) > +{ > + int ret, nid = NUMA_NO_NODE; I'm not overly keen to see the trivial rename of rc -> ret in here. Just makes it ever so slightly harder to compare old code and new code. > + > + BUG_ON(check_hotplug_memory_range(start, size)); > + > + /* > + * All memory blocks must be offlined before removing memory. Check > + * whether all memory blocks in question are offline and return error > + * if this is not the case. > + * > + * While at it, determine the nid. Note that if we'd have mixed nodes, > + * we'd only try to offline the last determined one -- which is good > + * enough for the cases we care about. > + */ > + ret = walk_memory_blocks(start, size, &nid, check_memblock_offlined_cb); > + if (ret) > + return ret; > + > + /* > + * For memmap_on_memory, the altmaps could have been added on > + * a per-memblock basis. Loop through the entire range if so, > + * and remove each memblock and its altmap. > + */ > + if (mhp_memmap_on_memory()) { > + unsigned long memblock_size = memory_block_size_bytes(); > + u64 cur_start; > + > + for (cur_start = start; cur_start < start + size; > + cur_start += memblock_size) > + __try_remove_memory(nid, cur_start, memblock_size); > + } else { > + __try_remove_memory(nid, start, size); > + } > + > return 0; > } > >
