linux-kernel - Re: [PATCH v3 1/8] iommu: Add MMIO mapping type

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Message-ID: <56C3197C.8090903@arm.com>
Date:	Tue, 16 Feb 2016 12:43:40 +0000
From:	Robin Murphy <robin.murphy@....com>
To:	Niklas Söderlund <niklas.soderlund@...natech.se>
Cc:	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	linux-renesas-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	dmaengine@...r.kernel.org, iommu@...ts.linux-foundation.org,
	vinod.koul@...el.com, geert+renesas@...der.be,
	linus.walleij@...aro.org, dan.j.williams@...el.com, arnd@...db.de,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH v3 1/8] iommu: Add MMIO mapping type

On 16/02/16 12:06, Niklas Söderlund wrote:
> Hi Robin,
>
> Thanks for your update patch I will include it in my next version. But
> I'm sorry I do not understand, is your modification an addition or a
> substitution to your original patch?

Apologies for being confusing - that was a diff on top of the existing 
patch, to be folded in. My original patch was only handling IOMMU_MMIO 
for stage 2 PTEs, so we also need the extra code to handle the different 
way of setting the appropriate memory type in stage 1 PTEs.

Robin.

> * Robin Murphy <robin.murphy@....com> [2016-02-11 15:57:26 +0000]:
>
>> On 11/02/16 00:02, Laurent Pinchart wrote:
>>> Hi Niklas,
>>>
>>> Thank you for the patch.
>>>
>>> On Wednesday 10 February 2016 01:57:51 Niklas Söderlund wrote:
>>>> From: Robin Murphy <robin.murphy@....com>
>>>>
>>>> On some platforms, MMIO regions might need slightly different treatment
>>>> compared to mapping regular memory; add the notion of MMIO mappings to
>>>> the IOMMU API's memory type flags, so that callers can let the IOMMU
>>>> drivers know to do the right thing.
>>>>
>>>> Signed-off-by: Robin Murphy <robin.murphy@....com>
>>>> Acked-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>>>
>>> Answering the question from the cover letter, yes, it's totally fine to pick
>>> the ack, that's actually expected.
>>>
>>>> ---
>>>>   drivers/iommu/io-pgtable-arm.c | 4 +++-
>>>>   include/linux/iommu.h          | 1 +
>>>
>>> You might be asked to split this patch in two.
>>
>> Worse than that, you might also be asked to fix it up when the silly author
>> remembers that he did this on a stage-2-only ARM SMMU, and the attributes
>> for the stage 1 tables that the IPMMU uses are in a different code path:
>>
>> --->8---
>> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
>> index 5b5c299..7622c6e 100644
>> --- a/drivers/iommu/io-pgtable-arm.c
>> +++ b/drivers/iommu/io-pgtable-arm.c
>> @@ -354,7 +354,10 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct
>> arm_lpae_io_pgtable *data,
>>                  if (!(prot & IOMMU_WRITE) && (prot & IOMMU_READ))
>>                          pte |= ARM_LPAE_PTE_AP_RDONLY;
>>
>> -               if (prot & IOMMU_CACHE)
>> +               if (prot & IOMMU_MMIO)
>> +                       pte |= (ARM_LPAE_MAIR_ATTR_IDX_DEV
>> +                               << ARM_LPAE_PTE_ATTRINDX_SHIFT);
>> +               else if (prot & IOMMU_CACHE)
>>                          pte |= (ARM_LPAE_MAIR_ATTR_IDX_CACHE
>>                                  << ARM_LPAE_PTE_ATTRINDX_SHIFT);
>>          } else {
>> --->8---
>>
>> Sorry for the bother,
>> Robin.
>>
>>>>   2 files changed, 4 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
>>>> index 381ca5a..3ff4f87 100644
>>>> --- a/drivers/iommu/io-pgtable-arm.c
>>>> +++ b/drivers/iommu/io-pgtable-arm.c
>>>> @@ -364,7 +364,9 @@ static arm_lpae_iopte arm_lpae_prot_to_pte(struct
>>>> arm_lpae_io_pgtable *data, pte |= ARM_LPAE_PTE_HAP_READ;
>>>>   		if (prot & IOMMU_WRITE)
>>>>   			pte |= ARM_LPAE_PTE_HAP_WRITE;
>>>> -		if (prot & IOMMU_CACHE)
>>>> +		if (prot & IOMMU_MMIO)
>>>> +			pte |= ARM_LPAE_PTE_MEMATTR_DEV;
>>>> +		else if (prot & IOMMU_CACHE)
>>>>   			pte |= ARM_LPAE_PTE_MEMATTR_OIWB;
>>>>   		else
>>>>   			pte |= ARM_LPAE_PTE_MEMATTR_NC;
>>>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>>>> index a5c539f..34b6432 100644
>>>> --- a/include/linux/iommu.h
>>>> +++ b/include/linux/iommu.h
>>>> @@ -30,6 +30,7 @@
>>>>   #define IOMMU_WRITE	(1 << 1)
>>>>   #define IOMMU_CACHE	(1 << 2) /* DMA cache coherency */
>>>>   #define IOMMU_NOEXEC	(1 << 3)
>>>> +#define IOMMU_MMIO	(1 << 4) /* e.g. things like MSI doorbells */
>>>>
>>>>   struct iommu_ops;
>>>>   struct iommu_group;
>>>
>>
>