From: Mike Rapoport <firstname.lastname@example.org> To: Anshuman Khandual <email@example.com> Cc: firstname.lastname@example.org, Ard Biesheuvel <email@example.com>, Catalin Marinas <firstname.lastname@example.org>, David Hildenbrand <email@example.com>, Marc Zyngier <firstname.lastname@example.org>, Mark Rutland <email@example.com>, Mike Rapoport <firstname.lastname@example.org>, Will Deacon <email@example.com>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, James Morse <email@example.com> Subject: Re: [RFC/RFT PATCH 0/3] arm64: drop pfn_valid_within() and simplify pfn_valid() Date: Thu, 8 Apr 2021 09:27:53 +0300 [thread overview] Message-ID: <YG6iaZJI/RiUwXzv@kernel.org> (raw) In-Reply-To: <firstname.lastname@example.org> On Thu, Apr 08, 2021 at 10:49:02AM +0530, Anshuman Khandual wrote: > Adding James here. > > + James Morse <email@example.com> > > On 4/7/21 10:56 PM, Mike Rapoport wrote: > > From: Mike Rapoport <firstname.lastname@example.org> > > > > Hi, > > > > These patches aim to remove CONFIG_HOLES_IN_ZONE and essentially hardwire > > pfn_valid_within() to 1. > > That would be really great for arm64 platform as it will save CPU cycles on > many generic MM paths, given that our pfn_valid() has been expensive. > > > > > The idea is to mark NOMAP pages as reserved in the memory map and restore > > Though I am not really sure, would that possibly be problematic for UEFI/EFI > use cases as it might have just treated them as normal struct pages till now. I don't think there should be a problem because now the struct pages for UEFI/ACPI never got to be used by the core mm. They were (rightfully) skipped by memblock_free_all() from one side and pfn_valid() and pfn_valid_within() return false for them in various pfn walkers from the other side. > > the intended semantics of pfn_valid() to designate availability of struct > > page for a pfn. > > Right, that would be better as the current semantics is not ideal. > > > > > With this the core mm will be able to cope with the fact that it cannot use > > NOMAP pages and the holes created by NOMAP ranges within MAX_ORDER blocks > > will be treated correctly even without the need for pfn_valid_within. > > > > The patches are only boot tested on qemu-system-aarch64 so I'd really > > appreciate memory stress tests on real hardware. > > Did some preliminary memory stress tests on a guest with portions of memory > marked as MEMBLOCK_NOMAP and did not find any obvious problem. But this might > require some testing on real UEFI environment with firmware using MEMBLOCK_NOMAP > memory to make sure that changing these struct pages to PageReserved() is safe. I surely have no access for such machines :) > > If this actually works we'll be one step closer to drop custom pfn_valid() > > on arm64 altogether. > > Right, planning to rework and respin the RFC originally sent last month. > > https://email@example.com/ -- Sincerely yours, Mike.
prev parent reply other threads:[~2021-04-08 6:28 UTC|newest] Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-04-07 17:26 Mike Rapoport 2021-04-07 17:26 ` [RFC/RFT PATCH 1/3] memblock: update initialization of reserved pages Mike Rapoport 2021-04-08 5:16 ` Anshuman Khandual 2021-04-08 5:48 ` Mike Rapoport 2021-04-14 15:12 ` David Hildenbrand 2021-04-14 15:27 ` Ard Biesheuvel 2021-04-14 15:52 ` David Hildenbrand 2021-04-14 20:24 ` Mike Rapoport 2021-04-15 9:30 ` David Hildenbrand 2021-04-16 11:44 ` Mike Rapoport 2021-04-16 11:54 ` David Hildenbrand 2021-04-14 20:11 ` Mike Rapoport 2021-04-14 20:06 ` Mike Rapoport 2021-04-07 17:26 ` [RFC/RFT PATCH 2/3] arm64: decouple check whether pfn is normal memory from pfn_valid() Mike Rapoport 2021-04-08 5:14 ` Anshuman Khandual 2021-04-08 6:00 ` Mike Rapoport 2021-04-14 15:58 ` David Hildenbrand 2021-04-14 20:29 ` Mike Rapoport 2021-04-15 9:31 ` David Hildenbrand 2021-04-16 11:40 ` Mike Rapoport 2021-04-07 17:26 ` [RFC/RFT PATCH 3/3] arm64: drop pfn_valid_within() and simplify pfn_valid() Mike Rapoport 2021-04-08 5:12 ` Anshuman Khandual 2021-04-08 6:17 ` Mike Rapoport 2021-04-08 5:19 ` [RFC/RFT PATCH 0/3] " Anshuman Khandual 2021-04-08 6:27 ` Mike Rapoport [this message]
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