From b1143537098b33affd4e50cec2c10e4b3858d93c Mon Sep 17 00:00:00 2001 From: Gregory Price Date: Mon, 27 Jan 2025 10:34:04 -0500 Subject: [PATCH] x86: probe memory block size advisement value during mm init Systems with hotplug may provide an advisement value on what the memblock size should be. Probe this value when the rest of the configuration values are considered. The new heuristic is as follows 1) set_memory_block_size_order value if already set (cmdline param) 2) minimum block size if memory is less than large block limit 3) if no hotplug advice: Max block size if system is bare-metal, otherwise use end of memory alignment. 4) if hotplug advice: lesser of advice and end of memory alignment. Convert to cpu_feature_enabled() while at it.[1] [1] https://lore.kernel.org/all/20241031103401.GBZyNdGQ-ZyXKyzC_z@fat_crate.local/ Link: https://lkml.kernel.org/r/20250127153405.3379117-3-gourry@gourry.net Signed-off-by: Gregory Price Suggested-by: Borislav Petkov Suggested-by: David Hildenbrand Acked-by: David Hildenbrand Acked-by: Dave Hansen Acked-by: Mike Rapoport (Microsoft) Acked-by: Dan Williams Tested-by: Fan Ni Reviewed-by: Ira Weiny Acked-by: Oscar Salvador Cc: Alison Schofield Cc: Andy Lutomirski Cc: Bruno Faccini Cc: Dave Jiang Cc: Greg Kroah-Hartman Cc: Haibo Xu Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Joanthan Cameron Cc: Len Brown Cc: Peter Zijlstra Cc: Rafael J. Wysocki Cc: Robert Richter Cc: Thomas Gleinxer Signed-off-by: Andrew Morton --- arch/x86/mm/init_64.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 7c4f6f591f2b..8cea7dcf8fa0 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -1464,16 +1464,21 @@ static unsigned long probe_memory_block_size(void) } /* - * Use max block size to minimize overhead on bare metal, where - * alignment for memory hotplug isn't a concern. + * When hotplug alignment is not a concern, maximize blocksize + * to minimize overhead. Otherwise, align to the lesser of advice + * alignment and end of memory alignment. */ - if (!boot_cpu_has(X86_FEATURE_HYPERVISOR)) { + bz = memory_block_advised_max_size(); + if (!bz) { bz = MAX_BLOCK_SIZE; - goto done; + if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) + goto done; + } else { + bz = max(min(bz, MAX_BLOCK_SIZE), MIN_MEMORY_BLOCK_SIZE); } /* Find the largest allowed block size that aligns to memory end */ - for (bz = MAX_BLOCK_SIZE; bz > MIN_MEMORY_BLOCK_SIZE; bz >>= 1) { + for (; bz > MIN_MEMORY_BLOCK_SIZE; bz >>= 1) { if (IS_ALIGNED(boot_mem_end, bz)) break; } -- 2.50.1