From: Philip Redkin me@rarity.fan
[ Upstream commit 631ca8909fd5c62b9fda9edda93924311a78a9c4 ]
At least with CONFIG_PHYSICAL_START=0x100000, if there is < 4 MiB of contiguous free memory available at this point, the kernel will crash and burn because memblock_phys_alloc_range() returns 0 on failure, which leads memblock_phys_free() to throw the first 4 MiB of physical memory to the wolves.
At a minimum it should fail gracefully with a meaningful diagnostic, but in fact everything seems to work fine without the weird reserve allocation.
Signed-off-by: Philip Redkin me@rarity.fan Signed-off-by: Ingo Molnar mingo@kernel.org Cc: Dave Hansen dave.hansen@linux.intel.com Cc: Rik van Riel riel@surriel.com Cc: "H. Peter Anvin" hpa@zytor.com Link: https://lore.kernel.org/r/94b3e98f-96a7-3560-1f76-349eb95ccf7f@rarity.fan Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/mm/init.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index ab697ee645288..446bf7fbc3250 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -654,8 +654,13 @@ static void __init memory_map_top_down(unsigned long map_start, */ addr = memblock_phys_alloc_range(PMD_SIZE, PMD_SIZE, map_start, map_end); - memblock_phys_free(addr, PMD_SIZE); - real_end = addr + PMD_SIZE; + if (!addr) { + pr_warn("Failed to release memory for alloc_low_pages()"); + real_end = max(map_start, ALIGN_DOWN(map_end, PMD_SIZE)); + } else { + memblock_phys_free(addr, PMD_SIZE); + real_end = addr + PMD_SIZE; + }
/* step_size need to be small so pgt_buf from BRK could cover it */ step_size = PMD_SIZE;