linux-kernel - Re: [PATCH] riscv: Only allow LTO with CMODEL_MEDANY

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Message-ID: <b0fdcb23-4d68-4d0f-a8ac-2b389a0ce856@ghiti.fr>
Date: Sat, 9 Aug 2025 12:45:59 +0200
From: Alexandre Ghiti <alex@...ti.fr>
To: Nathan Chancellor <nathan@...nel.org>, Palmer Dabbelt <palmer@...belt.com>
Cc: Conor Dooley <conor@...nel.org>, linux-riscv@...ts.infradead.org,
 llvm@...ts.linux.dev, linux-kernel@...r.kernel.org, stable@...r.kernel.org,
 kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] riscv: Only allow LTO with CMODEL_MEDANY

Hi Nathan,

On 8/8/25 23:53, Nathan Chancellor wrote:
> Ping? This is still getting hit.

This is the second time your patches do not reach the linux-riscv 
mailing list [1] [2], not even my personal mailbox.

[1] 
https://lore.kernel.org/linux-riscv/?q=riscv%3A+Only+allow+LTO+with+CMODEL_MEDANY 

[2] 
https://lore.kernel.org/linux-riscv/?q=riscv%3A+uaccess%3A+Fix+-Wuninitialized+and+-Wshadow+in+__put_user_nocheck

I don't know what's going on, do you have any idea?

I'll pick this up in my fixes branch.

Thanks,

Alex

>
> On Thu, Jul 10, 2025 at 01:25:26PM -0700, Nathan Chancellor wrote:
>> When building with CONFIG_CMODEL_MEDLOW and CONFIG_LTO_CLANG, there is a
>> series of errors due to some files being unconditionally compiled with
>> '-mcmodel=medany', mismatching with the rest of the kernel built with
>> '-mcmodel=medlow':
>>
>>    ld.lld: error: Function Import: link error: linking module flags 'Code Model': IDs have conflicting values: 'i32 3' from vmlinux.a(init.o at 899908), and 'i32 1' from vmlinux.a(net-traces.o at 1014628)
>>
>> Only allow LTO to be performed when CONFIG_CMODEL_MEDANY is enabled to
>> ensure there will be no code model mismatch errors. An alternative
>> solution would be disabling LTO for the files with a different code
>> model than the main kernel like some specialized areas of the kernel do
>> but doing that for individual files is not as sustainable than
>> forbidding the combination altogether.
>>
>> Cc: stable@...r.kernel.org
>> Fixes: 021d23428bdb ("RISC-V: build: Allow LTO to be selected")
>> Reported-by: kernel test robot <lkp@...el.com>
>> Closes: https://lore.kernel.org/oe-kbuild-all/202506290255.KBVM83vZ-lkp@intel.com/
>> Signed-off-by: Nathan Chancellor <nathan@...nel.org>
>> ---
>>   arch/riscv/Kconfig | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index 36061f4732b7..4eee737a050f 100644
>> --- a/arch/riscv/Kconfig
>> +++ b/arch/riscv/Kconfig
>> @@ -68,7 +68,7 @@ config RISCV
>>   	select ARCH_SUPPORTS_HUGE_PFNMAP if TRANSPARENT_HUGEPAGE
>>   	select ARCH_SUPPORTS_HUGETLBFS if MMU
>>   	# LLD >= 14: https://github.com/llvm/llvm-project/issues/50505
>> -	select ARCH_SUPPORTS_LTO_CLANG if LLD_VERSION >= 140000
>> +	select ARCH_SUPPORTS_LTO_CLANG if LLD_VERSION >= 140000 && CMODEL_MEDANY
>>   	select ARCH_SUPPORTS_LTO_CLANG_THIN if LLD_VERSION >= 140000
>>   	select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS if 64BIT && MMU
>>   	select ARCH_SUPPORTS_PAGE_TABLE_CHECK if MMU
>>
>> ---
>> base-commit: fda589c286040d9ba2d72a0eaf0a13945fc48026
>> change-id: 20250710-riscv-restrict-lto-to-medany-f1b7dd5c9bba
>>
>> Best regards,
>> --
>> Nathan Chancellor <nathan@...nel.org>
>>
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