Re: [RFC PATCH v1 00/57] Boot-time page size selection for arm64

Ryan Roberts
2024-10-24T12:13:08Z

On 24/10/2024 12:45, Petr Tesarik wrote:
> On Thu, 24 Oct 2024 11:48:55 +0100
> Ryan Roberts <ryan.roberts@arm.com> wrote:
>
>> On 23/10/2024 22:00, Thomas Tai wrote:
>>>
>>> On 10/17/2024 8:32 AM, Ryan Roberts wrote:
>>>> On 17/10/2024 13:27, Petr Tesarik wrote:
>>>>> On Mon, 14 Oct 2024 11:55:11 +0100
>>>>> Ryan Roberts <ryan.roberts@arm.com> wrote:
>>>>>
>>>>>> [...]
>>>>>> 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
>>>>> I have just tried to recompile the openSUSE kernel with these patches
>>>>> applied, and I'm running into this:
>>>>>
>>>>>    CC      arch/arm64/hyperv/hv_core.o
>>>>> In file included from ../arch/arm64/hyperv/hv_core.c:14:0:
>>>>> ../include/linux/hyperv.h:158:5: error: variably modified ‘reserved2’ at file
>>>>> scope
>>>>>    u8 reserved2[PAGE_SIZE - 68];
>>>>>       ^~~~~~~~~
>>>>>
>>>>> It looks like one more place which needs a patch, right?
>>>> As mentioned in the cover letter, so far I've only converted enough to get the
>>>> defconfig *image* building (i.e. no modules). If you are compiling a different
>>>> config or compiling the modules for defconfig, you will likely run into these
>>>> types of issues.
>>>
>>> It would be nice if you could provide the defconfig you are using; I also ran
>>> into build issues when using the arch/arm64/configs/defconfig.
>>
>> git clean -xdfq
>> make defconfig
>>
>> # Set CONFIG_ARM64_BOOT_TIME_PAGE_SIZE
>> ./scripts/config --disable CONFIG_ARM64_4K_PAGES
>> ./scripts/config --disable CONFIG_ARM64_16K_PAGES
>> ./scripts/config --disable CONFIG_ARM64_64K_PAGES
>> ./scripts/config --disable CONFIG_ARM64_BOOT_TIME_PAGE_SIZE
>> ./scripts/config --enable CONFIG_ARM64_BOOT_TIME_PAGE_SIZE
>>
>> # Set ARM64_VA_BITS_48
>> ./scripts/config --disable ARM64_VA_BITS_36
>> ./scripts/config --disable ARM64_VA_BITS_39
>> ./scripts/config --disable ARM64_VA_BITS_42
>> ./scripts/config --disable ARM64_VA_BITS_47
>> ./scripts/config --disable ARM64_VA_BITS_48
>> ./scripts/config --disable ARM64_VA_BITS_52
>> ./scripts/config --enable ARM64_VA_BITS_48
>>
>> # Optional: filesystems known to compile with boot-time page size
>> ./scripts/config --enable CONFIG_SQUASHFS_LZ4
>> ./scripts/config --enable CONFIG_SQUASHFS_LZO
>> ./scripts/config --enable CONFIG_SQUASHFS_XZ
>> ./scripts/config --enable CONFIG_SQUASHFS_ZSTD
>> ./scripts/config --enable CONFIG_XFS_FS
>>
>> # Optional: trace stuff known to compile with boot-time page size
>> ./scripts/config --enable CONFIG_FTRACE
>> ./scripts/config --enable CONFIG_FUNCTION_TRACER
>> ./scripts/config --enable CONFIG_KPROBES
>> ./scripts/config --enable CONFIG_HIST_TRIGGERS
>> ./scripts/config --enable CONFIG_FTRACE_SYSCALLS
>>
>> # Optional: misc mm stuff known to compile with boot-time page size
>> ./scripts/config --enable CONFIG_PTDUMP_DEBUGFS
>> ./scripts/config --enable CONFIG_READ_ONLY_THP_FOR_FS
>> ./scripts/config --enable CONFIG_USERFAULTFD
>>
>> # Optional: mm debug stuff known compile with boot-time page size
>> ./scripts/config --enable CONFIG_DEBUG_VM
>> ./scripts/config --enable CONFIG_DEBUG_VM_MAPLE_TREE
>> ./scripts/config --enable CONFIG_DEBUG_VM_RB
>> ./scripts/config --enable CONFIG_DEBUG_VM_PGFLAGS
>> ./scripts/config --enable CONFIG_DEBUG_VM_PGTABLE
>> ./scripts/config --enable CONFIG_PAGE_TABLE_CHECK
>> ./scripts/config --enable CONFIG_PAGE_TABLE_CHECK_ENFORCED
>>
>> make olddefconfig
>> make -s -j`nproc` Image
>>
>> So I'm explicitly only building and booting the kernel image, not the modules.
>> The kernel image contains all the drivers needed to get a VM up and running
>> under QEMU/KVM.
>
> FWIW with the attached patch I was also able to boot the kernel on
> Ampere Altra bare metal and using modules.

Nice!

Thanks for the below. That was already reported and I have a fix in my branch at
[1]. That also includes the btrfs patch you sent and the hyper-v patches, as
well as other fixups from review.

[1]
https://gitlab.arm.com/linux-arm/linux-rr/-/tree/features/boot-time-page-size-v2-wip

Thanks,
Ryan

>
> Petr T
>
> diff --git a/arch/arm64/mm/pgtable-geometry.c b/arch/arm64/mm/pgtable-geometry.c
> index ba50637f1e9d..4eb074b99654 100644
> --- a/arch/arm64/mm/pgtable-geometry.c
> +++ b/arch/arm64/mm/pgtable-geometry.c
> @@ -15,8 +15,14 @@
> */
>
> int ptg_page_shift __read_mostly;
> +EXPORT_SYMBOL_GPL(ptg_page_shift);
> +
> int ptg_pmd_shift __read_mostly;
> +EXPORT_SYMBOL_GPL(ptg_pmd_shift);
> +
> int ptg_pud_shift __read_mostly;
> +EXPORT_SYMBOL_GPL(ptg_pud_shift);
> +
> int ptg_p4d_shift __read_mostly;
> int ptg_pgdir_shift __read_mostly;
> int ptg_cont_pte_shift __read_mostly;