linux-kernel - Re: [PATCH] iommu: PGTABLE

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Message-ID: <4dbba30e-9c7a-ec73-8a5b-deda182e7f08@infradead.org>
Date:   Thu, 30 Mar 2023 09:33:59 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Conor Dooley <conor.dooley@...rochip.com>,
        linux-kernel@...r.kernel.org, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>, iommu@...ts.linux.dev,
        Conor Dooley <conor@...nel.org>,
        linux-riscv@...ts.infradead.org, geert+renesas@...der.be
Subject: Re: [PATCH] iommu: PGTABLE_LPAE is also for RISCV

Hi--

On 3/30/23 09:11, Geert Uytterhoeven wrote:
> Hi Randy,
> 
> On Thu, Mar 30, 2023 at 5:48 PM Randy Dunlap <rdunlap@...radead.org> wrote:
>> On 3/30/23 00:31, Geert Uytterhoeven wrote:
>>> On Thu, Mar 30, 2023 at 8:25 AM Conor Dooley <conor.dooley@...rochip.com> wrote:
>>>> On Wed, Mar 29, 2023 at 11:01:05PM -0700, Randy Dunlap wrote:
>>>>> On riscv64, linux-next-20233030 (and for several days earlier),
>>>>> there is a kconfig warning:
>>>>>
>>>>> WARNING: unmet direct dependencies detected for IOMMU_IO_PGTABLE_LPAE
>>>>>   Depends on [n]: IOMMU_SUPPORT [=y] && (ARM || ARM64 || COMPILE_TEST [=n]) && !GENERIC_ATOMIC64 [=n]
>>>>>   Selected by [y]:
>>>>>   - IPMMU_VMSA [=y] && IOMMU_SUPPORT [=y] && (ARCH_RENESAS [=y] || COMPILE_TEST [=n]) && !GENERIC_ATOMIC64 [=n]
>>>>>
>>>>> and build errors:
>>>>>
>>>>> riscv64-linux-ld: drivers/iommu/io-pgtable-arm.o: in function `.L140':
>>>>> io-pgtable-arm.c:(.init.text+0x1e8): undefined reference to `alloc_io_pgtable_ops'
>>>>> riscv64-linux-ld: drivers/iommu/io-pgtable-arm.o: in function `.L168':
>>>>> io-pgtable-arm.c:(.init.text+0xab0): undefined reference to `free_io_pgtable_ops'
>>>>> riscv64-linux-ld: drivers/iommu/ipmmu-vmsa.o: in function `.L140':
>>>>> ipmmu-vmsa.c:(.text+0xbc4): undefined reference to `free_io_pgtable_ops'
>>>>> riscv64-linux-ld: drivers/iommu/ipmmu-vmsa.o: in function `.L0 ':
>>>>> ipmmu-vmsa.c:(.text+0x145e): undefined reference to `alloc_io_pgtable_ops'
>>>>>
>>>>> Add RISCV as an allowed ARCH dependency to fix these problems.
>>>>>
>>>>> Fixes: d286a58bc8f4 ("iommu: Tidy up io-pgtable dependencies")
>>>>> Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
>>>>> Cc: Joerg Roedel <joro@...tes.org>
>>>>> Cc: Will Deacon <will@...nel.org>
>>>>> Cc: Robin Murphy <robin.murphy@....com>
>>>>> Cc: iommu@...ts.linux.dev
>>>>> Cc: Conor Dooley <conor@...nel.org>
>>>>> Cc: linux-riscv@...ts.infradead.org
>>>>> ---
>>>>>  drivers/iommu/Kconfig |    2 +-
>>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff -- a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
>>>>> --- a/drivers/iommu/Kconfig
>>>>> +++ b/drivers/iommu/Kconfig
>>>>> @@ -32,7 +32,7 @@ config IOMMU_IO_PGTABLE
>>>>>  config IOMMU_IO_PGTABLE_LPAE
>>>>>       bool "ARMv7/v8 Long Descriptor Format"
>>>>
>>>> I'm probably missing something here, but why would we want to enable
>>>> "ARMv7/v8 Long Descriptor Format" on RISC-V?
>>>
>>> Indeed, we should not enable it, unless compile-testing.
>>>
>>>> Would it not be better to make the Renesas depend on, rather than
>>>> select the option? It does seem highly arch specific, and I feel like
>>>> Geert previously mentioned that the RZ/Five (their RISC-V offering)
>>>> didn't use it.
>>>
>>> I think the IPMMU_VMSA dependency should gain
>>>
>>>         depends on ARM || ARM64 || COMPILE_TEST
>>
>> so like this?
>> Or did you mean to drop the ARCH_RENESAS part also?
>>
>>
>>  config IPMMU_VMSA
>>         bool "Renesas VMSA-compatible IPMMU"
>> -       depends on ARCH_RENESAS || COMPILE_TEST
>> +       depends on ARCH_RENESAS || ARM || ARM64 || COMPILE_TEST
> 
> No, you want "depends on (ARCH_RENESAS && (ARM || ARM64)) || COMPILE_TEST",
> which is a bit hard to read.
> 
> Hence I really meant adding that line, i.e.:
> 
>      config IPMMU_VMSA
>            bool "Renesas VMSA-compatible IPMMU"
>            depends on ARCH_RENESAS || COMPILE_TEST
>     +      depends on ARM || ARM64 || COMPILE_TEST
> 

OK, that fixes the kconfig warning and the build errors.
I can read the first method easier that the second one, but I'll
go with your suggestion. Hopefully no one will come along and
"fix it up" but instead muck it up.

Thanks.
-- 
~Randy