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Message-ID: <1634d3e0-ac13-4f08-97e3-9b04a9202431@arm.com>
Date: Wed, 18 Oct 2023 09:21:02 +0100
From: Ryan Roberts <ryan.roberts@....com>
To: Catalin Marinas <catalin.marinas@....com>
Cc: kernel test robot <lkp@...el.com>, Will Deacon <will@...nel.org>,
Steven Price <steven.price@....com>,
Peter Collingbourne <pcc@...gle.com>, llvm@...ts.linux.dev,
oe-kbuild-all@...ts.linux.dev,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arm64/mm: Hoist synchronization out of set_ptes() loop
On 17/10/2023 13:57, Catalin Marinas wrote:
> On Tue, Oct 17, 2023 at 08:36:43AM +0100, Ryan Roberts wrote:
>> On 16/10/2023 18:54, Catalin Marinas wrote:
>>> On Sat, Oct 14, 2023 at 05:15:51AM +0800, kernel test robot wrote:
>>>> kernel test robot noticed the following build warnings:
>>>>
>>>> [auto build test WARNING on arm64/for-next/core]
>>>> [also build test WARNING on arm-perf/for-next/perf arm/for-next kvmarm/next soc/for-next linus/master v6.6-rc5 next-20231013]
>>>> [cannot apply to arm/fixes]
>>>> [If your patch is applied to the wrong git tree, kindly drop us a note.
>>>> And when submitting patch, we suggest to use '--base' as documented in
>>>> https://git-scm.com/docs/git-format-patch#_base_tree_information]
>>>>
>>>> url: https://github.com/intel-lab-lkp/linux/commits/Ryan-Roberts/arm64-mm-Hoist-synchronization-out-of-set_ptes-loop/20231005-231636
>>>> base: https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/core
>>>> patch link: https://lore.kernel.org/r/20231005140730.2191134-1-ryan.roberts%40arm.com
>>>> patch subject: [PATCH v2] arm64/mm: Hoist synchronization out of set_ptes() loop
>>>> config: arm64-allyesconfig (https://download.01.org/0day-ci/archive/20231014/202310140531.BQQwt3NQ-lkp@intel.com/config)
>>>> compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project.git 4a5ac14ee968ff0ad5d2cc1ffa0299048db4c88a)
>>>> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231014/202310140531.BQQwt3NQ-lkp@intel.com/reproduce)
>>>>
>>>> If you fix the issue in a separate patch/commit (i.e. not just a new version of
>>>> the same patch/commit), kindly add following tags
>>>> | Reported-by: kernel test robot <lkp@...el.com>
>>>> | Closes: https://lore.kernel.org/oe-kbuild-all/202310140531.BQQwt3NQ-lkp@intel.com/
>>>>
>>>> All warnings (new ones prefixed by >>):
>>>>
>>>> In file included from net/ipv4/route.c:66:
>>>> In file included from include/linux/mm.h:29:
>>>> In file included from include/linux/pgtable.h:6:
>>>>>> arch/arm64/include/asm/pgtable.h:344:65: warning: parameter 'addr' set but not used [-Wunused-but-set-parameter]
>>>> 344 | static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
>>>> | ^
>>>> 1 warning generated.
>>>
>>> Thanks for the report. I think something like below will do (I'll test
>>> and commit as a separate patch, it's not something that Ryan's patch
>>> introduces):
>>
>> I was actually just trying to repro this and was planning to send out a v3 of my
>> patch. But if you are happy to handle it as you suggest, then I guess you don't
>> need anything further from me?
>
> If you feel like testing, please give this a go ;)
Compile tested and observed that warning is gone with your change. Also ran mm
selftests and all looks good. So:
Tested-by: Ryan Roberts <ryan.roberts@....com>
>
> ------------8<---------------------------
> From e6255237acfc21e92252653c3ed42446ef67f625 Mon Sep 17 00:00:00 2001
> From: Catalin Marinas <catalin.marinas@....com>
> Date: Tue, 17 Oct 2023 11:57:55 +0100
> Subject: [PATCH] arm64: Mark the 'addr' argument to set_ptes() and
> __set_pte_at() as unused
>
> This argument is not used by the arm64 implementation. Mark it as
> __always_unused and also remove the unnecessary 'addr' increment in
> set_ptes().
>
> Signed-off-by: Catalin Marinas <catalin.marinas@....com>
> Reported-by: kernel test robot <lkp@...el.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202310140531.BQQwt3NQ-lkp@intel.com/
> Cc: Will Deacon <will@...nel.org>
> Cc: Ryan Roberts <ryan.roberts@....com>
> ---
> arch/arm64/include/asm/pgtable.h | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 68984ba9ce2a..b19a8aee684c 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -341,8 +341,9 @@ static inline void __sync_cache_and_tags(pte_t pte, unsigned int nr_pages)
> mte_sync_tags(pte, nr_pages);
> }
>
> -static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
> - pte_t *ptep, pte_t pte, unsigned int nr)
> +static inline void set_ptes(struct mm_struct *mm,
> + unsigned long __always_unused addr,
Personally I'm not a huge fan of the __always_unused mark up, given that it's
used so patchily in the source. The warning also disappears without these
markups. (the real problem is just the `addr += PAGE_SIZE` below.
Thanks,
Ryan
> + pte_t *ptep, pte_t pte, unsigned int nr)
> {
> page_table_check_ptes_set(mm, ptep, pte, nr);
> __sync_cache_and_tags(pte, nr);
> @@ -353,7 +354,6 @@ static inline void set_ptes(struct mm_struct *mm, unsigned long addr,
> if (--nr == 0)
> break;
> ptep++;
> - addr += PAGE_SIZE;
> pte_val(pte) += PAGE_SIZE;
> }
> }
> @@ -528,7 +528,8 @@ static inline pmd_t pmd_mkdevmap(pmd_t pmd)
> #define pud_pfn(pud) ((__pud_to_phys(pud) & PUD_MASK) >> PAGE_SHIFT)
> #define pfn_pud(pfn,prot) __pud(__phys_to_pud_val((phys_addr_t)(pfn) << PAGE_SHIFT) | pgprot_val(prot))
>
> -static inline void __set_pte_at(struct mm_struct *mm, unsigned long addr,
> +static inline void __set_pte_at(struct mm_struct *mm,
> + unsigned long __always_unused addr,
> pte_t *ptep, pte_t pte, unsigned int nr)
> {
> __sync_cache_and_tags(pte, nr);
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