From: Greg Kroah-Hartman gregkh@linuxfoundation.org
From: Anshuman Khandual anshuman.khandual@arm.com
[ Upstream commit eeb0753ba27b26f609e61f9950b14f1b934fe429 ]
pfn_valid() validates a pfn but basically it checks for a valid struct page backing for that pfn. It should always return positive for memory ranges backed with struct page mapping. But currently pfn_valid() fails for all ZONE_DEVICE based memory types even though they have struct page mapping.
pfn_valid() asserts that there is a memblock entry for a given pfn without MEMBLOCK_NOMAP flag being set. The problem with ZONE_DEVICE based memory is that they do not have memblock entries. Hence memblock_is_map_memory() will invariably fail via memblock_search() for a ZONE_DEVICE based address. This eventually fails pfn_valid() which is wrong. memblock_is_map_memory() needs to be skipped for such memory ranges. As ZONE_DEVICE memory gets hotplugged into the system via memremap_pages() called from a driver, their respective memory sections will not have SECTION_IS_EARLY set.
Normal hotplug memory will never have MEMBLOCK_NOMAP set in their memblock regions. Because the flag MEMBLOCK_NOMAP was specifically designed and set for firmware reserved memory regions. memblock_is_map_memory() can just be skipped as its always going to be positive and that will be an optimization for the normal hotplug memory. Like ZONE_DEVICE based memory, all normal hotplugged memory too will not have SECTION_IS_EARLY set for their sections
Skipping memblock_is_map_memory() for all non early memory sections would fix pfn_valid() problem for ZONE_DEVICE based memory and also improve its performance for normal hotplug memory as well.
Cc: Catalin Marinas catalin.marinas@arm.com Cc: Will Deacon will@kernel.org Cc: Ard Biesheuvel ardb@kernel.org Cc: Robin Murphy robin.murphy@arm.com Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org Acked-by: David Hildenbrand david@redhat.com Fixes: 73b20c84d42d ("arm64: mm: implement pte_devmap support") Signed-off-by: Anshuman Khandual anshuman.khandual@arm.com Acked-by: Catalin Marinas catalin.marinas@arm.com Link: https://lore.kernel.org/r/1614921898-4099-2-git-send-email-anshuman.khandual... Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/mm/init.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 602bd19630ff..cbcac03c0e0d 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -245,6 +245,18 @@ int pfn_valid(unsigned long pfn)
if (!valid_section(__nr_to_section(pfn_to_section_nr(pfn)))) return 0; + + /* + * ZONE_DEVICE memory does not have the memblock entries. + * memblock_is_map_memory() check for ZONE_DEVICE based + * addresses will always fail. Even the normal hotplugged + * memory will never have MEMBLOCK_NOMAP flag set in their + * memblock entries. Skip memblock search for all non early + * memory sections covering all of hotplug memory including + * both normal and ZONE_DEVICE based. + */ + if (!early_section(__pfn_to_section(pfn))) + return pfn_section_valid(__pfn_to_section(pfn), pfn); #endif return memblock_is_map_memory(addr); }