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Message-ID: <872f1c9c-9fb2-4372-810d-abe5419c4bd8@arm.com> Date: Mon, 21 Oct 2024 16:01:52 +0100 From: Ryan Roberts <ryan.roberts@....com> To: Neal Gompa <neal@...pa.dev> Cc: Eric Curtin <ecurtin@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, Anshuman Khandual <anshuman.khandual@....com>, Ard Biesheuvel <ardb@...nel.org>, Catalin Marinas <catalin.marinas@....com>, David Hildenbrand <david@...hat.com>, Greg Marsden <greg.marsden@...cle.com>, Ivan Ivanov <ivan.ivanov@...e.com>, Kalesh Singh <kaleshsingh@...gle.com>, Marc Zyngier <maz@...nel.org>, Mark Rutland <mark.rutland@....com>, Matthias Brugger <mbrugger@...e.com>, Miroslav Benes <mbenes@...e.cz>, Will Deacon <will@...nel.org>, Hector Martin <marcan@...can.st>, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-mm@...ck.org, asahi@...ts.linux.dev Subject: Re: [RFC PATCH v1 00/57] Boot-time page size selection for arm64 On 21/10/2024 14:49, Neal Gompa wrote: > On Mon, Oct 21, 2024 at 7:51 AM Ryan Roberts <ryan.roberts@....com> wrote: >> >> On 21/10/2024 12:32, Eric Curtin wrote: >>> On Mon, 21 Oct 2024 at 12:09, Ryan Roberts <ryan.roberts@....com> wrote: >>>> >>>> On 19/10/2024 16:47, Neal Gompa wrote: >>>>> On Monday, October 14, 2024 6:55:11 AM EDT Ryan Roberts wrote: >>>>>> Hi All, >>>>>> >>>>>> Patch bomb incoming... This covers many subsystems, so I've included a core >>>>>> set of people on the full series and additionally included maintainers on >>>>>> relevant patches. I haven't included those maintainers on this cover letter >>>>>> since the numbers were far too big for it to work. But I've included a link >>>>>> to this cover letter on each patch, so they can hopefully find their way >>>>>> here. For follow up submissions I'll break it up by subsystem, but for now >>>>>> thought it was important to show the full picture. >>>>>> >>>>>> This RFC series implements support for boot-time page size selection within >>>>>> the arm64 kernel. arm64 supports 3 base page sizes (4K, 16K, 64K), but to >>>>>> date, page size has been selected at compile-time, meaning the size is >>>>>> baked into a given kernel image. As use of larger-than-4K page sizes become >>>>>> more prevalent this starts to present a problem for distributions. >>>>>> Boot-time page size selection enables the creation of a single kernel >>>>>> image, which can be told which page size to use on the kernel command line. >>>>>> >>>>>> Why is having an image-per-page size problematic? >>>>>> ================================================= >>>>>> >>>>>> Many traditional distros are now supporting both 4K and 64K. And this means >>>>>> managing 2 kernel packages, along with drivers for each. For some, it means >>>>>> multiple installer flavours and multiple ISOs. All of this adds up to a >>>>>> less-than-ideal level of complexity. Additionally, Android now supports 4K >>>>>> and 16K kernels. I'm told having to explicitly manage their KABI for each >>>>>> kernel is painful, and the extra flash space required for both kernel >>>>>> images and the duplicated modules has been problematic. Boot-time page size >>>>>> selection solves all of this. >>>>>> >>>>>> Additionally, in starting to think about the longer term deployment story >>>>>> for D128 page tables, which Arm architecture now supports, a lot of the >>>>>> same problems need to be solved, so this work sets us up nicely for that. >>>>>> >>>>>> So what's the down side? >>>>>> ======================== >>>>>> >>>>>> Well nothing's free; Various static allocations in the kernel image must be >>>>>> sized for the worst case (largest supported page size), so image size is in >>>>>> line with size of 64K compile-time image. So if you're interested in 4K or >>>>>> 16K, there is a slight increase to the image size. But I expect that >>>>>> problem goes away if you're compressing the image - its just some extra >>>>>> zeros. At boot-time, I expect we could free the unused static storage once >>>>>> we know the page size - although that would be a follow up enhancement. >>>>>> >>>>>> And then there is performance. Since PAGE_SIZE and friends are no longer >>>>>> compile-time constants, we must look up their values and do arithmetic at >>>>>> runtime instead of compile-time. My early perf testing suggests this is >>>>>> inperceptible for real-world workloads, and only has small impact on >>>>>> microbenchmarks - more on this below. >>>>>> >>>>>> Approach >>>>>> ======== >>>>>> >>>>>> The basic idea is to rid the source of any assumptions that PAGE_SIZE and >>>>>> friends are compile-time constant, but in a way that allows the compiler to >>>>>> perform the same optimizations as was previously being done if they do turn >>>>>> out to be compile-time constant. Where constants are required, we use >>>>>> limits; PAGE_SIZE_MIN and PAGE_SIZE_MAX. See commit log in patch 1 for full >>>>>> description of all the classes of problems to solve. >>>>>> >>>>>> By default PAGE_SIZE_MIN=PAGE_SIZE_MAX=PAGE_SIZE. But an arch may opt-in to >>>>>> boot-time page size selection by defining PAGE_SIZE_MIN & PAGE_SIZE_MAX. >>>>>> arm64 does this if the user selects the CONFIG_ARM64_BOOT_TIME_PAGE_SIZE >>>>>> Kconfig, which is an alternative to selecting a compile-time page size. >>>>>> >>>>>> When boot-time page size is active, the arch pgtable geometry macro >>>>>> definitions resolve to something that can be configured at boot. The arm64 >>>>>> implementation in this series mainly uses global, __ro_after_init >>>>>> variables. I've tried using alternatives patching, but that performs worse >>>>>> than loading from memory; I think due to code size bloat. >>>>>> >>>>>> Status >>>>>> ====== >>>>>> >>>>>> When CONFIG_ARM64_BOOT_TIME_PAGE_SIZE is selected, I've only implemented >>>>>> enough to compile the kernel image itself with defconfig (and a few other >>>>>> bits and pieces). This is enough to build a kernel that can boot under QEMU >>>>>> or FVP. I'll happily do the rest of the work to enable all the extra >>>>>> drivers, but wanted to get feedback on the shape of this effort first. If >>>>>> anyone wants to do any testing, and has a must-have config, let me know and >>>>>> I'll prioritize enabling it first. >>>>>> >>>>>> The series is arranged as follows: >>>>>> >>>>>> - patch 1: Add macros required for converting non-arch code to support >>>>>> boot-time page size selection >>>>>> - patches 2-36: Remove PAGE_SIZE compile-time constant assumption from >>>>>> all non-arch code >>>>>> - patches 37-38: Some arm64 tidy ups >>>>>> - patch 39: Add macros required for converting arm64 code to >>>>> support >>>>>> boot-time page size selection >>>>>> - patches 40-56: arm64 changes to support boot-time page size selection >>>>>> - patch 57: Add arm64 Kconfig option to enable boot-time page >>>>> size >>>>>> selection >>>>>> >>>>>> Ideally, I'd like to get the basics merged (something like this series), >>>>>> then incrementally improve it over a handful of kernel releases until we >>>>>> can demonstrate that we have feature parity with the compile-time build and >>>>>> no performance blockers. Once at that point, ideally the compile-time build >>>>>> options would be removed and the code could be cleaned up further. >>>>>> >>>>>> One of the bigger peices that I'd propose to add as a follow up, is to make >>>>>> va-size boot-time selectable too. That will greatly simplify LPA2 fallback >>>>>> handling. >>>>>> >>>>>> Assuming people are ammenable to the rough shape, how would I go about >>>>>> getting the non-arch changes merged? Since they cover many subsystems, will >>>>>> each piece need to go independently to each relevant maintainer or could it >>>>>> all be merged together through the arm64 tree? >>>>>> >>>>>> Image Size >>>>>> ========== >>>>>> >>>>>> The below shows the size of a defconfig (+ xfs, squashfs, ftrace, kprobes) >>>>>> kernel image on disk for base (before any changes applied), compile (with >>>>>> changes, configured for compile-time page size) and boot (with changes, >>>>>> configured for boot-time page size). >>>>>> >>>>>> You can see the that compile-16k and 64k configs are actually slightly >>>>>> smaller than the baselines; that's due to optimizing some buffer sizes >>>>>> which didn't need to depend on page size during the series. The boot-time >>>>>> image is ~1% bigger than the 64k compile-time image. I believe there is >>>>>> scope to improve this to make it >>>>>> equal to compile-64k if required: >>>>>> | config | size/KB | diff/KB | diff/% | >>>>>> | >>>>>> |-------------|---------|---------|---------| >>>>>> | >>>>>> | base-4k | 54895 | 0 | 0.0% | >>>>>> | base-16k | 55161 | 266 | 0.5% | >>>>>> | base-64k | 56775 | 1880 | 3.4% | >>>>>> | compile-4k | 54895 | 0 | 0.0% | >>>>>> | compile-16k | 55097 | 202 | 0.4% | >>>>>> | compile-64k | 56391 | 1496 | 2.7% | >>>>>> | boot-4K | 57045 | 2150 | 3.9% | >>>>>> >>>>>> And below shows the size of the image in memory at run-time, separated for >>>>>> text and data costs. The boot image has ~1% text cost; most likely due to >>>>>> the fact that PAGE_SIZE and friends are not compile-time constants so need >>>>>> instructions to load the values and do arithmetic. I believe we could >>>>>> eventually get the data cost to match the cost for the compile image for >>>>>> the chosen page size by freeing >>>>>> the ends of the static buffers not needed for the selected page size: >>>>>> | | text | text | text | data | data | data | >>>>>> | >>>>>> | config | size/KB | diff/KB | diff/% | size/KB | diff/KB | diff/% | >>>>>> | >>>>>> |-------------|---------|---------|---------|---------|---------|---------| >>>>>> | >>>>>> | base-4k | 20561 | 0 | 0.0% | 14314 | 0 | 0.0% | >>>>>> | base-16k | 20439 | -122 | -0.6% | 14625 | 311 | 2.2% | >>>>>> | base-64k | 20435 | -126 | -0.6% | 15673 | 1359 | 9.5% | >>>>>> | compile-4k | 20565 | 4 | 0.0% | 14315 | 1 | 0.0% | >>>>>> | compile-16k | 20443 | -118 | -0.6% | 14517 | 204 | 1.4% | >>>>>> | compile-64k | 20439 | -122 | -0.6% | 15134 | 820 | 5.7% | >>>>>> | boot-4K | 20811 | 250 | 1.2% | 15287 | 973 | 6.8% | >>>>>> >>>>>> Functional Testing >>>>>> ================== >>>>>> >>>>>> I've build-tested defconfig for all arches supported by tuxmake (which is >>>>>> most) without issue. >>>>>> >>>>>> I've boot-tested arm64 with CONFIG_ARM64_BOOT_TIME_PAGE_SIZE for all page >>>>>> sizes and a few va-sizes, and additionally have run all the mm-selftests, >>>>>> with no regressions observed vs the equivalent compile-time page size build >>>>>> (although the mm-selftests have a few existing failures when run against >>>>>> 16K and 64K kernels - those should really be investigated and fixed >>>>>> independently). >>>>>> >>>>>> Test coverage is lacking for many of the drivers that I've touched, but in >>>>>> many cases, I'm hoping the changes are simple enough that review might >>>>>> suffice? >>>>>> >>>>>> Performance Testing >>>>>> =================== >>>>>> >>>>>> I've run some limited performance benchmarks: >>>>>> >>>>>> First, a real-world benchmark that causes a lot of page table manipulation >>>>>> (and therefore we would expect to see regression here if we are going to >>>>>> see it anywhere); kernel compilation. It barely registers a change. Values >>>>>> are times, >>>>>> so smaller is better. All relative to base-4k: >>>>>> | | kern | kern | user | user | real | real | >>>>>> | >>>>>> | config | mean | stdev | mean | stdev | mean | stdev | >>>>>> | >>>>>> |-------------|---------|---------|---------|---------|---------|---------| >>>>>> | >>>>>> | base-4k | 0.0% | 1.1% | 0.0% | 0.3% | 0.0% | 0.3% | >>>>>> | compile-4k | -0.2% | 1.1% | -0.2% | 0.3% | -0.1% | 0.3% | >>>>>> | boot-4k | 0.1% | 1.0% | -0.3% | 0.2% | -0.2% | 0.2% | >>>>>> >>>>>> The Speedometer JavaScript benchmark also shows no change. Values are runs >>>>>> per >>>>>> min, so bigger is better. All relative to base-4k: >>>>>> | config | mean | stdev | >>>>>> | >>>>>> |-------------|---------|---------| >>>>>> | >>>>>> | base-4k | 0.0% | 0.8% | >>>>>> | compile-4k | 0.4% | 0.8% | >>>>>> | boot-4k | 0.0% | 0.9% | >>>>>> >>>>>> Finally, I've run some microbenchmarks known to stress page table >>>>>> manipulations (originally from David Hildenbrand). The fork test >>>>>> maps/allocs 1G of anon memory, then measures the cost of fork(). The munmap >>>>>> test maps/allocs 1G of anon memory then measures the cost of munmap()ing >>>>>> it. The fork test is known to be extremely sensitive to any changes that >>>>>> cause instructions to be aligned differently in cachelines. When using this >>>>>> test for other changes, I've seen double digit regressions for the >>>>>> slightest thing, so 12% regression on this test is actually fairly good. >>>>>> This likely represents the extreme worst case for regressions that will be >>>>>> observed across other microbenchmarks (famous last >>>>>> words). Values are times, so smaller is better. All relative to base-4k: >>>>>> | | fork | fork | munmap | munmap | >>>>>> | >>>>>> | config | mean | stdev | stdev | stdev | >>>>>> | >>>>>> |-------------|---------|---------|---------|---------| >>>>>> | >>>>>> | base-4k | 0.0% | 1.3% | 0.0% | 0.3% | >>>>>> | compile-4k | 0.1% | 1.3% | -0.9% | 0.1% | >>>>>> | boot-4k | 12.8% | 1.2% | 3.8% | 1.0% | >>>>>> >>>>>> NOTE: The series applies on top of v6.11. >>>>>> >>>>>> Thanks, >>>>>> Ryan >>>>>> >>>>>> >>>>>> Ryan Roberts (57): >>>>>> mm: Add macros ahead of supporting boot-time page size selection >>>>>> vmlinux: Align to PAGE_SIZE_MAX >>>>>> mm/memcontrol: Fix seq_buf size to save memory when PAGE_SIZE is large >>>>>> mm/page_alloc: Make page_frag_cache boot-time page size compatible >>>>>> mm: Avoid split pmd ptl if pmd level is run-time folded >>>>>> mm: Remove PAGE_SIZE compile-time constant assumption >>>>>> fs: Introduce MAX_BUF_PER_PAGE_SIZE_MAX for array sizing >>>>>> fs: Remove PAGE_SIZE compile-time constant assumption >>>>>> fs/nfs: Remove PAGE_SIZE compile-time constant assumption >>>>>> fs/ext4: Remove PAGE_SIZE compile-time constant assumption >>>>>> fork: Permit boot-time THREAD_SIZE determination >>>>>> cgroup: Remove PAGE_SIZE compile-time constant assumption >>>>>> bpf: Remove PAGE_SIZE compile-time constant assumption >>>>>> pm/hibernate: Remove PAGE_SIZE compile-time constant assumption >>>>>> stackdepot: Remove PAGE_SIZE compile-time constant assumption >>>>>> perf: Remove PAGE_SIZE compile-time constant assumption >>>>>> kvm: Remove PAGE_SIZE compile-time constant assumption >>>>>> trace: Remove PAGE_SIZE compile-time constant assumption >>>>>> crash: Remove PAGE_SIZE compile-time constant assumption >>>>>> crypto: Remove PAGE_SIZE compile-time constant assumption >>>>>> sunrpc: Remove PAGE_SIZE compile-time constant assumption >>>>>> sound: Remove PAGE_SIZE compile-time constant assumption >>>>>> net: Remove PAGE_SIZE compile-time constant assumption >>>>>> net: fec: Remove PAGE_SIZE compile-time constant assumption >>>>>> net: marvell: Remove PAGE_SIZE compile-time constant assumption >>>>>> net: hns3: Remove PAGE_SIZE compile-time constant assumption >>>>>> net: e1000: Remove PAGE_SIZE compile-time constant assumption >>>>>> net: igbvf: Remove PAGE_SIZE compile-time constant assumption >>>>>> net: igb: Remove PAGE_SIZE compile-time constant assumption >>>>>> drivers/base: Remove PAGE_SIZE compile-time constant assumption >>>>>> edac: Remove PAGE_SIZE compile-time constant assumption >>>>>> optee: Remove PAGE_SIZE compile-time constant assumption >>>>>> random: Remove PAGE_SIZE compile-time constant assumption >>>>>> sata_sil24: Remove PAGE_SIZE compile-time constant assumption >>>>>> virtio: Remove PAGE_SIZE compile-time constant assumption >>>>>> xen: Remove PAGE_SIZE compile-time constant assumption >>>>>> arm64: Fix macros to work in C code in addition to the linker script >>>>>> arm64: Track early pgtable allocation limit >>>>>> arm64: Introduce macros required for boot-time page selection >>>>>> arm64: Refactor early pgtable size calculation macros >>>>>> arm64: Pass desired page size on command line >>>>>> arm64: Divorce early init from PAGE_SIZE >>>>>> arm64: Clean up simple cases of CONFIG_ARM64_*K_PAGES >>>>>> arm64: Align sections to PAGE_SIZE_MAX >>>>>> arm64: Rework trampoline rodata mapping >>>>>> arm64: Generalize fixmap for boot-time page size >>>>>> arm64: Statically allocate and align for worst-case page size >>>>>> arm64: Convert switch to if for non-const comparison values >>>>>> arm64: Convert BUILD_BUG_ON to VM_BUG_ON >>>>>> arm64: Remove PAGE_SZ asm-offset >>>>>> arm64: Introduce cpu features for page sizes >>>>>> arm64: Remove PAGE_SIZE from assembly code >>>>>> arm64: Runtime-fold pmd level >>>>>> arm64: Support runtime folding in idmap_kpti_install_ng_mappings >>>>>> arm64: TRAMP_VALIAS is no longer compile-time constant >>>>>> arm64: Determine THREAD_SIZE at boot-time >>>>>> arm64: Enable boot-time page size selection >>>>>> >>>>>> arch/alpha/include/asm/page.h | 1 + >>>>>> arch/arc/include/asm/page.h | 1 + >>>>>> arch/arm/include/asm/page.h | 1 + >>>>>> arch/arm64/Kconfig | 26 ++- >>>>>> arch/arm64/include/asm/assembler.h | 78 ++++++- >>>>>> arch/arm64/include/asm/cpufeature.h | 44 +++- >>>>>> arch/arm64/include/asm/efi.h | 2 +- >>>>>> arch/arm64/include/asm/fixmap.h | 28 ++- >>>>>> arch/arm64/include/asm/kernel-pgtable.h | 150 +++++++++---- >>>>>> arch/arm64/include/asm/kvm_arm.h | 21 +- >>>>>> arch/arm64/include/asm/kvm_hyp.h | 11 + >>>>>> arch/arm64/include/asm/kvm_pgtable.h | 6 +- >>>>>> arch/arm64/include/asm/memory.h | 62 ++++-- >>>>>> arch/arm64/include/asm/page-def.h | 3 +- >>>>>> arch/arm64/include/asm/pgalloc.h | 16 +- >>>>>> arch/arm64/include/asm/pgtable-geometry.h | 46 ++++ >>>>>> arch/arm64/include/asm/pgtable-hwdef.h | 28 ++- >>>>>> arch/arm64/include/asm/pgtable-prot.h | 2 +- >>>>>> arch/arm64/include/asm/pgtable.h | 133 +++++++++--- >>>>>> arch/arm64/include/asm/processor.h | 10 +- >>>>>> arch/arm64/include/asm/sections.h | 1 + >>>>>> arch/arm64/include/asm/smp.h | 1 + >>>>>> arch/arm64/include/asm/sparsemem.h | 15 +- >>>>>> arch/arm64/include/asm/sysreg.h | 54 +++-- >>>>>> arch/arm64/include/asm/tlb.h | 3 + >>>>>> arch/arm64/kernel/asm-offsets.c | 4 +- >>>>>> arch/arm64/kernel/cpufeature.c | 93 ++++++-- >>>>>> arch/arm64/kernel/efi.c | 2 +- >>>>>> arch/arm64/kernel/entry.S | 60 +++++- >>>>>> arch/arm64/kernel/head.S | 46 +++- >>>>>> arch/arm64/kernel/hibernate-asm.S | 6 +- >>>>>> arch/arm64/kernel/image-vars.h | 14 ++ >>>>>> arch/arm64/kernel/image.h | 4 + >>>>>> arch/arm64/kernel/pi/idreg-override.c | 68 +++++- >>>>>> arch/arm64/kernel/pi/map_kernel.c | 165 ++++++++++---- >>>>>> arch/arm64/kernel/pi/map_range.c | 201 ++++++++++++++++-- >>>>>> arch/arm64/kernel/pi/pi.h | 63 +++++- >>>>>> arch/arm64/kernel/relocate_kernel.S | 10 +- >>>>>> arch/arm64/kernel/vdso-wrap.S | 4 +- >>>>>> arch/arm64/kernel/vdso.c | 7 +- >>>>>> arch/arm64/kernel/vdso/vdso.lds.S | 4 +- >>>>>> arch/arm64/kernel/vdso32-wrap.S | 4 +- >>>>>> arch/arm64/kernel/vdso32/vdso.lds.S | 4 +- >>>>>> arch/arm64/kernel/vmlinux.lds.S | 48 +++-- >>>>>> arch/arm64/kvm/arm.c | 10 + >>>>>> arch/arm64/kvm/hyp/nvhe/Makefile | 1 + >>>>>> arch/arm64/kvm/hyp/nvhe/host.S | 10 +- >>>>>> arch/arm64/kvm/hyp/nvhe/hyp.lds.S | 4 +- >>>>>> arch/arm64/kvm/hyp/nvhe/pgtable-geometry.c | 16 ++ >>>>>> arch/arm64/kvm/mmu.c | 39 ++-- >>>>>> arch/arm64/lib/clear_page.S | 7 +- >>>>>> arch/arm64/lib/copy_page.S | 33 ++- >>>>>> arch/arm64/lib/mte.S | 27 ++- >>>>>> arch/arm64/mm/Makefile | 1 + >>>>>> arch/arm64/mm/fixmap.c | 38 ++-- >>>>>> arch/arm64/mm/hugetlbpage.c | 40 +--- >>>>>> arch/arm64/mm/init.c | 26 +-- >>>>>> arch/arm64/mm/kasan_init.c | 8 +- >>>>>> arch/arm64/mm/mmu.c | 53 +++-- >>>>>> arch/arm64/mm/pgd.c | 12 +- >>>>>> arch/arm64/mm/pgtable-geometry.c | 24 +++ >>>>>> arch/arm64/mm/proc.S | 128 ++++++++--- >>>>>> arch/arm64/mm/ptdump.c | 3 +- >>>>>> arch/arm64/tools/cpucaps | 3 + >>>>>> arch/csky/include/asm/page.h | 3 + >>>>>> arch/hexagon/include/asm/page.h | 2 + >>>>>> arch/loongarch/include/asm/page.h | 2 + >>>>>> arch/m68k/include/asm/page.h | 1 + >>>>>> arch/microblaze/include/asm/page.h | 1 + >>>>>> arch/mips/include/asm/page.h | 1 + >>>>>> arch/nios2/include/asm/page.h | 2 + >>>>>> arch/openrisc/include/asm/page.h | 1 + >>>>>> arch/parisc/include/asm/page.h | 1 + >>>>>> arch/powerpc/include/asm/page.h | 2 + >>>>>> arch/riscv/include/asm/page.h | 1 + >>>>>> arch/s390/include/asm/page.h | 1 + >>>>>> arch/sh/include/asm/page.h | 1 + >>>>>> arch/sparc/include/asm/page.h | 3 + >>>>>> arch/um/include/asm/page.h | 2 + >>>>>> arch/x86/include/asm/page_types.h | 2 + >>>>>> arch/xtensa/include/asm/page.h | 1 + >>>>>> crypto/lskcipher.c | 4 +- >>>>>> drivers/ata/sata_sil24.c | 46 ++-- >>>>>> drivers/base/node.c | 6 +- >>>>>> drivers/base/topology.c | 32 +-- >>>>>> drivers/block/virtio_blk.c | 2 +- >>>>>> drivers/char/random.c | 4 +- >>>>>> drivers/edac/edac_mc.h | 13 +- >>>>>> drivers/firmware/efi/libstub/arm64.c | 3 +- >>>>>> drivers/irqchip/irq-gic-v3-its.c | 2 +- >>>>>> drivers/mtd/mtdswap.c | 4 +- >>>>>> drivers/net/ethernet/freescale/fec.h | 3 +- >>>>>> drivers/net/ethernet/freescale/fec_main.c | 5 +- >>>>>> .../net/ethernet/hisilicon/hns3/hns3_enet.h | 4 +- >>>>>> drivers/net/ethernet/intel/e1000/e1000_main.c | 6 +- >>>>>> drivers/net/ethernet/intel/igb/igb.h | 25 +-- >>>>>> drivers/net/ethernet/intel/igb/igb_main.c | 149 +++++++------ >>>>>> drivers/net/ethernet/intel/igbvf/netdev.c | 6 +- >>>>>> drivers/net/ethernet/marvell/mvneta.c | 9 +- >>>>>> drivers/net/ethernet/marvell/sky2.h | 2 +- >>>>>> drivers/tee/optee/call.c | 7 +- >>>>>> drivers/tee/optee/smc_abi.c | 2 +- >>>>>> drivers/virtio/virtio_balloon.c | 10 +- >>>>>> drivers/xen/balloon.c | 11 +- >>>>>> drivers/xen/biomerge.c | 12 +- >>>>>> drivers/xen/privcmd.c | 2 +- >>>>>> drivers/xen/xenbus/xenbus_client.c | 5 +- >>>>>> drivers/xen/xlate_mmu.c | 6 +- >>>>>> fs/binfmt_elf.c | 11 +- >>>>>> fs/buffer.c | 2 +- >>>>>> fs/coredump.c | 8 +- >>>>>> fs/ext4/ext4.h | 36 ++-- >>>>>> fs/ext4/move_extent.c | 2 +- >>>>>> fs/ext4/readpage.c | 2 +- >>>>>> fs/fat/dir.c | 4 +- >>>>>> fs/fat/fatent.c | 4 +- >>>>>> fs/nfs/nfs42proc.c | 2 +- >>>>>> fs/nfs/nfs42xattr.c | 2 +- >>>>>> fs/nfs/nfs4proc.c | 2 +- >>>>>> include/asm-generic/pgtable-geometry.h | 71 +++++++ >>>>>> include/asm-generic/vmlinux.lds.h | 38 ++-- >>>>>> include/linux/buffer_head.h | 1 + >>>>>> include/linux/cpumask.h | 5 + >>>>>> include/linux/linkage.h | 4 +- >>>>>> include/linux/mm.h | 17 +- >>>>>> include/linux/mm_types.h | 15 +- >>>>>> include/linux/mm_types_task.h | 2 +- >>>>>> include/linux/mmzone.h | 3 +- >>>>>> include/linux/netlink.h | 6 +- >>>>>> include/linux/percpu-defs.h | 4 +- >>>>>> include/linux/perf_event.h | 2 +- >>>>>> include/linux/sched.h | 4 +- >>>>>> include/linux/slab.h | 7 +- >>>>>> include/linux/stackdepot.h | 6 +- >>>>>> include/linux/sunrpc/svc.h | 8 +- >>>>>> include/linux/sunrpc/svc_rdma.h | 4 +- >>>>>> include/linux/sunrpc/svcsock.h | 2 +- >>>>>> include/linux/swap.h | 17 +- >>>>>> include/linux/swapops.h | 6 +- >>>>>> include/linux/thread_info.h | 10 +- >>>>>> include/xen/page.h | 2 + >>>>>> init/main.c | 7 +- >>>>>> kernel/bpf/core.c | 9 +- >>>>>> kernel/bpf/ringbuf.c | 54 ++--- >>>>>> kernel/cgroup/cgroup.c | 8 +- >>>>>> kernel/crash_core.c | 2 +- >>>>>> kernel/events/core.c | 2 +- >>>>>> kernel/fork.c | 71 +++---- >>>>>> kernel/power/power.h | 2 +- >>>>>> kernel/power/snapshot.c | 2 +- >>>>>> kernel/power/swap.c | 129 +++++++++-- >>>>>> kernel/trace/fgraph.c | 2 +- >>>>>> kernel/trace/trace.c | 2 +- >>>>>> lib/stackdepot.c | 6 +- >>>>>> mm/kasan/report.c | 3 +- >>>>>> mm/memcontrol.c | 11 +- >>>>>> mm/memory.c | 4 +- >>>>>> mm/mmap.c | 2 +- >>>>>> mm/page-writeback.c | 2 +- >>>>>> mm/page_alloc.c | 31 +-- >>>>>> mm/slub.c | 2 +- >>>>>> mm/sparse.c | 2 +- >>>>>> mm/swapfile.c | 2 +- >>>>>> mm/vmalloc.c | 7 +- >>>>>> net/9p/trans_virtio.c | 4 +- >>>>>> net/core/hotdata.c | 4 +- >>>>>> net/core/skbuff.c | 4 +- >>>>>> net/core/sysctl_net_core.c | 2 +- >>>>>> net/sunrpc/cache.c | 3 +- >>>>>> net/unix/af_unix.c | 2 +- >>>>>> sound/soc/soc-utils.c | 4 +- >>>>>> virt/kvm/kvm_main.c | 2 +- >>>>>> 172 files changed, 2185 insertions(+), 951 deletions(-) >>>>>> create mode 100644 arch/arm64/include/asm/pgtable-geometry.h >>>>>> create mode 100644 arch/arm64/kvm/hyp/nvhe/pgtable-geometry.c >>>>>> create mode 100644 arch/arm64/mm/pgtable-geometry.c >>>>>> create mode 100644 include/asm-generic/pgtable-geometry.h >>>>>> >>>>>> -- >>>>>> 2.43.0 >>>>> >>>>> This is a generally very exciting patch set! I'm looking forward to seeing it >>>>> land so I can take advantage of it for Fedora ARM and Fedora Asahi Remix. >>>>> >>>>> That said, I have a couple of questions: >>>>> >>>>> * Going forward, how would we handle drivers/modules that require a particular >>>>> page size? For example, the Apple Silicon IOMMU driver code requires the >>>>> kernel to operate in 16k page size mode, and it would need to be disabled in >>>>> other page sizes. >>>> >>>> I think these drivers would want to check PAGE_SIZE at probe time and fail if an >>>> unsupported page size is in use. Do you see any issue with that? >>>> >>>>> >>>>> * How would we handle an invalid selection at boot? >>>> >>>> What do you mean by invalid here? The current policy validates that the >>>> requested page size is supported by the HW by checking mmfr0. If no page size is >>>> passed on the command line, or the passed value is not supported by the HW, then >>>> the we default to the largest page size supported by the HW (so for Apple >>>> Silicon that would be 16k since the HW doesn't support 64k). Although I think it >>>> may be better to change that policy to use the smallest page size in this case; >>>> 4k is the safer bet for compat and will waste much less memory than 64k. >>>> >>>>> Can we program in a >>>>> fallback when the "wrong" mode is selected for a chip or something similar? >>>> >>>> Do you mean effectively add a machanism to force 16k if the detected HW is Apple >>>> Silicon? The trouble is that we need to select the page size, very early in >>>> boot, before start_kernel() is called, so we really only have generic arch code >>>> and the command line with which to make the decision. >>> >>> Yes... I think a build-time CONFIG for default page size, which can be >>> overridden by a karg makes sense... Even on platforms like Apple >>> Silicon you may want to test very specific things in 4k by overriding >>> with a karg. >> >> Ahh, yes, that would certainly work. I'll work it into the next version. >> > > Could we maybe extend to have some kind of way to include a table of > SoC IDs that certain modes are disabled (e.g. 64k on Apple Silicon) 64k is already disabled on Apple Silicon because mmfr0 reports that 64k is not supported. > and preferred modes when no arg is set (16k for Apple Silicon)? That And it's not obvious that we should hard-code a page size preference to a SoC ID. If the CPU can support multiple page sizes, it should be up to the SW stack to decide, not the SoC. I'm guessing your desire is to have a single kernel build that will boot 16k by default on Apple Silicon and 4k by default on other systems, all without needing to modify the command line? Personally I think it's cleaner to just require setting the page size on the command line in these cases. > way it'd work something like this: > > 1. Table identification of 4/16/64 depending on identified SoC So I'd prefer not to have this > 2. Unidentified ones follow build-time default > 3. karg forces a mode regardless But keep these 2. > >
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