On Wed, Apr 21, 2021 at 04:36:46PM +0530, Anshuman Khandual wrote: > > On 4/21/21 12:21 PM, Mike Rapoport wrote: > > From: Mike Rapoport <rppt@xxxxxxxxxxxxx> > > > > The arm64's version of pfn_valid() differs from the generic because of two > > reasons: > > > > * Parts of the memory map are freed during boot. This makes it necessary to > > verify that there is actual physical memory that corresponds to a pfn > > which is done by querying memblock. > > > > * There are NOMAP memory regions. These regions are not mapped in the > > linear map and until the previous commit the struct pages representing > > these areas had default values. > > > > As the consequence of absence of the special treatment of NOMAP regions in > > the memory map it was necessary to use memblock_is_map_memory() in > > pfn_valid() and to have pfn_valid_within() aliased to pfn_valid() so that > > generic mm functionality would not treat a NOMAP page as a normal page. > > > > Since the NOMAP regions are now marked as PageReserved(), pfn walkers and > > the rest of core mm will treat them as unusable memory and thus > > pfn_valid_within() is no longer required at all and can be disabled by > > removing CONFIG_HOLES_IN_ZONE on arm64. > > This makes sense. > > > > > pfn_valid() can be slightly simplified by replacing > > memblock_is_map_memory() with memblock_is_memory(). > > > > Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> > > --- > > arch/arm64/Kconfig | 3 --- > > arch/arm64/mm/init.c | 4 ++-- > > 2 files changed, 2 insertions(+), 5 deletions(-) > > > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > > index e4e1b6550115..58e439046d05 100644 > > --- a/arch/arm64/Kconfig > > +++ b/arch/arm64/Kconfig > > @@ -1040,9 +1040,6 @@ config NEED_PER_CPU_EMBED_FIRST_CHUNK > > def_bool y > > depends on NUMA > > > > -config HOLES_IN_ZONE > > - def_bool y > > - > > Right. > > > source "kernel/Kconfig.hz" > > > > config ARCH_SPARSEMEM_ENABLE > > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > > index dc03bdc12c0f..eb3f56fb8c7c 100644 > > --- a/arch/arm64/mm/init.c > > +++ b/arch/arm64/mm/init.c > > @@ -243,7 +243,7 @@ int pfn_valid(unsigned long pfn) > > > > /* > > * ZONE_DEVICE memory does not have the memblock entries. > > - * memblock_is_map_memory() check for ZONE_DEVICE based > > + * memblock_is_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 > > @@ -254,7 +254,7 @@ int pfn_valid(unsigned long pfn) > > return pfn_section_valid(ms, pfn); > > } > > #endif > > - return memblock_is_map_memory(addr); > > + return memblock_is_memory(addr); > > Wondering if MEMBLOCK_NOMAP is now being treated similarly to other > memory pfns for page table walking purpose but with PageReserved(), > why memblock_is_memory() is still required ? At this point, should > not we just return valid for early_section() memory. As pfn_valid() > now just implies that pfn has a struct page backing which has been > already verified with valid_section() etc. memblock_is_memory() is required because arm64 frees unused parts of the memory map. So, for instance, if we have 64M out of 128M populated in a section the section based calculation would return 1 for a pfn in the second half of the section, but there would be no memory map there. > > } > > EXPORT_SYMBOL(pfn_valid); > > > > -- Sincerely yours, Mike.
