From: David Hildenbrand <email@example.com> To: Anshuman Khandual <firstname.lastname@example.org>, email@example.com, firstname.lastname@example.org, email@example.com Cc: "Catalin Marinas" <firstname.lastname@example.org>, "Will Deacon" <email@example.com>, "Ard Biesheuvel" <firstname.lastname@example.org>, "Mark Rutland" <email@example.com>, "James Morse" <firstname.lastname@example.org>, "Robin Murphy" <email@example.com>, "Jérôme Glisse" <firstname.lastname@example.org>, "Dan Williams" <email@example.com>, "Mike Rapoport" <firstname.lastname@example.org> Subject: Re: [PATCH 1/2] arm64/mm: Fix pfn_valid() for ZONE_DEVICE based memory Date: Fri, 29 Jan 2021 10:58:59 +0100 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <firstname.lastname@example.org> On 29.01.21 08:39, Anshuman Khandual wrote: > 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 <email@example.com> > Cc: Will Deacon <firstname.lastname@example.org> > Cc: Ard Biesheuvel <email@example.com> > Cc: Robin Murphy <firstname.lastname@example.org> > Cc: email@example.com > Cc: firstname.lastname@example.org > Fixes: 73b20c84d42d ("arm64: mm: implement pte_devmap support") > Signed-off-by: Anshuman Khandual <email@example.com> > --- > 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 709d98fea90c..1141075e4d53 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -230,6 +230,18 @@ int pfn_valid(unsigned long pfn) > > if (!valid_section(__pfn_to_section(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); > } > LGTM Acked-by: David Hildenbrand <firstname.lastname@example.org> -- Thanks, David / dhildenb
next prev parent reply other threads:[~2021-01-29 9:59 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-01-29 7:39 [PATCH 0/2] " Anshuman Khandual 2021-01-29 7:39 ` [PATCH 1/2] " Anshuman Khandual 2021-01-29 9:58 ` David Hildenbrand [this message] 2021-01-29 7:39 ` [PATCH 2/2] arm64/mm: Reorganize pfn_valid() Anshuman Khandual 2021-01-29 10:07 ` David Hildenbrand 2021-02-01 3:47 ` Anshuman Khandual
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