On 21/10/2024 12:32, Eric Curtin wrote: > On Mon, 21 Oct 2024 at 12:09, Ryan Roberts <ryan.roberts@xxxxxxx> 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. > > Like in downstream kernels like Fedora/RHEL/etc. I would expect the > default would be 4k, but you could override with 16k, 64k, etc. with a > karg. > >> >>>> Thanks again and best regards! >>> >>> (P.S.: Please add the asahi@ mailing list to the CC for future iterations of >>> this patch set and tag both Hector and myself in as well. Thanks!) >> >> Will do! >> >>> >>> >> >> >
