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

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Message-ID: <068c45ae-dd60-7ab6-ee08-64f95a85f510@arm.com>
Date:   Thu, 30 Mar 2023 11:43:29 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Conor Dooley <conor.dooley@...rochip.com>
Cc:     Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        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

On 2023-03-30 08:31, Geert Uytterhoeven wrote:
> Hi Conor,
> 
> 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

Indeed, I thought we'd settled on something like that in the previous 
thread(s) on ARCH_RENESAS vs. RV32, but I guess nobody got round to 
actually respininng the patch (possibly since my refactoring here ended 
up papering over the immediate RV32 issue).

Cheers,
Robin.

>>>        select IOMMU_IO_PGTABLE
>>> -     depends on ARM || ARM64 || COMPILE_TEST
>>> +     depends on ARM || ARM64 || RISCV || COMPILE_TEST
>>>        depends on !GENERIC_ATOMIC64    # for cmpxchg64()
>>>        help
>>>          Enable support for the ARM long descriptor pagetable format.
> 
> Gr{oetje,eeting}s,
> 
>                          Geert
>