From: Chris Clayton <chris2553@googlemail.com>
To: Will Deacon <will.deacon@arm.com>
Cc: LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] iommu: prompt for IOMMU_IO_PGTABLE_LPAE on ARM archs only
Date: Mon, 16 Feb 2015 19:25:39 +0000 [thread overview]
Message-ID: <54E24433.6070308@googlemail.com> (raw)
In-Reply-To: <20150216163247.GM10634@arm.com>
On 02/16/15 16:32, Will Deacon wrote:
> Hi Chris,
>
> On Sun, Feb 15, 2015 at 11:17:19AM +0000, Chris Clayton wrote:
>> When running "make oldconfig" for an x86_64 kernel, I was prompted for a
>> setting for IOMMU_IO_PGTABLE_LPAE. From the prompt and the help text it
>> appears that this config item is relevant to ARMv7/v8 only. This patch
>> prevents the prompt on non-ARM architectures. Compile tested building a
>> cross-compiled x86_64 kernel in an x86 user space. The resultant kernel
>> boots fine and I am running it now.
>>
>> Fixes: e1d3c0fd701df831169b116cd5c5d6203ac07f70
>> Cc: will.deacon@arm.com
>> Signed-off-by: Chris Clayton <chris2553@googlemail.com>
>>
>> --- linux/drivers/iommu/Kconfig.orig 2015-02-15 09:44:01.235927248 +0000
>> +++ linux/drivers/iommu/Kconfig 2015-02-15 09:44:41.131926434 +0000
>> @@ -22,6 +22,7 @@ config IOMMU_IO_PGTABLE
>>
>> config IOMMU_IO_PGTABLE_LPAE
>> bool "ARMv7/v8 Long Descriptor Format"
>> + depends on ARM || ARM64
>> select IOMMU_IO_PGTABLE
>> help
>> Enable support for the ARM long descriptor pagetable format.
>
> What's the problem with this? The page-table code is intentionally
> decoupled from the CPU architecture and having this boot-tested on x86
> found some real bugs that I'm currently fixing. Sure, you probably don't
> need this on your box, but it's not default y and you don't have to
> select it.
>
There's no real problem except that, as I said, the prompt and the help text suggest that the config is relevant to ARM
architecture only. Same with the help text. When it popped up on x86_64, it was a surprise.
As you say, I can simply answer "N", but the prompt and the help need correcting, because for an ordinary Joe User like
me, it's misleading.
> Will
>
prev parent reply other threads:[~2015-02-16 19:25 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-15 11:17 [PATCH] iommu: prompt for IOMMU_IO_PGTABLE_LPAE on ARM archs only Chris Clayton
2015-02-16 16:32 ` Will Deacon
2015-02-16 19:25 ` Chris Clayton [this message]
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