[PATCH] iommu/io-pgtable-arm: Don't use dma_to_phys()

[PATCH] iommu/io-pgtable-arm: Don't use dma_to_phys()

[Robin Murphy]

In checking whether DMA addresses differ from physical addresses, using
dma_to_phys() is actually the wrong thing to do, since it may hide any
DMA offset, which is precisely one of the things we are checking for.
Simply casting between the two address types, whilst ugly, is in fact
the appropriate course of action.

We can also reject any device with a fixed DMA offset up-front at page
table creation, leaving the allocation-time check for the more subtle
cases like bounce buffering due to an incorrect DMA mask.

Furthermore, we can then fix the hackish KConfig dependency so that
architectures without a dma_to_phys() implementation may still
COMPILE_TEST (or even use!) the code. The true dependency is on the
DMA API, so use the appropriate symbol for that.

Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
---
 drivers/iommu/Kconfig          |  3 +--
 drivers/iommu/io-pgtable-arm.c | 16 ++++++++--------
 2 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 4664c2a..3dc1bcb 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -23,8 +23,7 @@ config IOMMU_IO_PGTABLE
 config IOMMU_IO_PGTABLE_LPAE
 	bool "ARMv7/v8 Long Descriptor Format"
 	select IOMMU_IO_PGTABLE
-	# SWIOTLB guarantees a dma_to_phys() implementation
-	depends on ARM || ARM64 || (COMPILE_TEST && SWIOTLB)
+	depends on HAS_DMA && (ARM || ARM64 || COMPILE_TEST)
 	help
 	  Enable support for the ARM long descriptor pagetable format.
 	  This allocator supports 4K/2M/1G, 16K/32M and 64K/512M page
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 73c0748..e7f9ab9 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -202,11 +202,6 @@ typedef u64 arm_lpae_iopte;
 
 static bool selftest_running = false;
 
-static dma_addr_t __arm_lpae_dma_addr(struct device *dev, void *pages)
-{
-	return phys_to_dma(dev, virt_to_phys(pages));
-}
-
 static void *__arm_lpae_alloc_pages(size_t size, gfp_t gfp,
 				    struct io_pgtable_cfg *cfg)
 {
@@ -226,7 +221,7 @@ static void *__arm_lpae_alloc_pages(size_t size, gfp_t gfp,
 		 * address directly, so if the DMA layer suggests it can't by
 		 * giving us back some translation, that bodes very badly...
 		 */
-		if (dma != __arm_lpae_dma_addr(dev, pages))
+		if ((u64)dma != (u64)virt_to_phys(pages))
 			goto out_unmap;
 	}
 
@@ -246,7 +241,7 @@ static void __arm_lpae_free_pages(void *pages, size_t size,
 	struct device *dev = cfg->iommu_dev;
 
 	if (!selftest_running)
-		dma_unmap_single(dev, __arm_lpae_dma_addr(dev, pages),
+		dma_unmap_single(dev, (dma_addr_t)virt_to_phys(pages),
 				 size, DMA_TO_DEVICE);
 	free_pages_exact(pages, size);
 }
@@ -259,7 +254,7 @@ static void __arm_lpae_set_pte(arm_lpae_iopte *ptep, arm_lpae_iopte pte,
 	*ptep = pte;
 
 	if (!selftest_running)
-		dma_sync_single_for_device(dev, __arm_lpae_dma_addr(dev, ptep),
+		dma_sync_single_for_device(dev, (dma_addr_t)virt_to_phys(ptep),
 					   sizeof(pte), DMA_TO_DEVICE);
 }
 
@@ -629,6 +624,11 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg)
 	if (cfg->oas > ARM_LPAE_MAX_ADDR_BITS)
 		return NULL;
 
+	if (cfg->iommu_dev->dma_pfn_offset) {
+		dev_err(cfg->iommu_dev, "Cannot accommodate DMA offset for IOMMU page tables\n");
+		return NULL;
+	}
+
 	data = kmalloc(sizeof(*data), GFP_KERNEL);
 	if (!data)
 		return NULL;
-- 
1.9.1

Re: [PATCH] iommu/io-pgtable-arm: Don't use dma_to_phys()

[Will Deacon]

On Thu, Sep 17, 2015 at 03:22:20PM +0100, Robin Murphy wrote:
> In checking whether DMA addresses differ from physical addresses, using
> dma_to_phys() is actually the wrong thing to do, since it may hide any
> DMA offset, which is precisely one of the things we are checking for.
> Simply casting between the two address types, whilst ugly, is in fact
> the appropriate course of action.

Urgh... yes.

> We can also reject any device with a fixed DMA offset up-front at page
> table creation, leaving the allocation-time check for the more subtle
> cases like bounce buffering due to an incorrect DMA mask.
> 
> Furthermore, we can then fix the hackish KConfig dependency so that
> architectures without a dma_to_phys() implementation may still
> COMPILE_TEST (or even use!) the code. The true dependency is on the
> DMA API, so use the appropriate symbol for that.
> 
> Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
> ---
>  drivers/iommu/Kconfig          |  3 +--
>  drivers/iommu/io-pgtable-arm.c | 16 ++++++++--------
>  2 files changed, 9 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index 4664c2a..3dc1bcb 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -23,8 +23,7 @@ config IOMMU_IO_PGTABLE
>  config IOMMU_IO_PGTABLE_LPAE
>  	bool "ARMv7/v8 Long Descriptor Format"
>  	select IOMMU_IO_PGTABLE
> -	# SWIOTLB guarantees a dma_to_phys() implementation
> -	depends on ARM || ARM64 || (COMPILE_TEST && SWIOTLB)
> +	depends on HAS_DMA && (ARM || ARM64 || COMPILE_TEST)
>  	help
>  	  Enable support for the ARM long descriptor pagetable format.
>  	  This allocator supports 4K/2M/1G, 16K/32M and 64K/512M page
> diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
> index 73c0748..e7f9ab9 100644
> --- a/drivers/iommu/io-pgtable-arm.c
> +++ b/drivers/iommu/io-pgtable-arm.c
> @@ -202,11 +202,6 @@ typedef u64 arm_lpae_iopte;
>  
>  static bool selftest_running = false;
>  
> -static dma_addr_t __arm_lpae_dma_addr(struct device *dev, void *pages)
> -{
> -	return phys_to_dma(dev, virt_to_phys(pages));
> -}

Can we keep this helper kicking around, at least to contain the ugliness
of the virt_to_phys + cast?

Will

Re: [PATCH] iommu/io-pgtable-arm: Don't use dma_to_phys()

[Robin Murphy]

On 17/09/15 15:52, Will Deacon wrote:
[...]
>> -static dma_addr_t __arm_lpae_dma_addr(struct device *dev, void *pages)
>> -{
>> -	return phys_to_dma(dev, virt_to_phys(pages));
>> -}
>
> Can we keep this helper kicking around, at least to contain the ugliness
> of the virt_to_phys + cast?

Can do for the sync and unmap cases - the alloc_pages one needs to avoid 
truncation in the comparison if dma_addr_t and phys_addr_t are different 
sizes, so can't safely cast one to the other either way. I can at least 
get rid of the u64 casts there though, as they seem superfluous after a 
bit of experimentation and another read of the good old "Usual 
arithmetic conversions". I'll fix up and repost.

Robin.

>
> Will
>

[PATCH v2] iommu/io-pgtable-arm: Don't use dma_to_phys()

[Robin Murphy]

In checking whether DMA addresses differ from physical addresses, using
dma_to_phys() is actually the wrong thing to do, since it may hide any
DMA offset, which is precisely one of the things we are checking for.
Simply casting between the two address types, whilst ugly, is in fact
the appropriate course of action. Further care (and ugliness) is also
necessary in the comparison to avoid truncation if phys_addr_t and
dma_addr_t differ in size.

We can also reject any device with a fixed DMA offset up-front at page
table creation, leaving the allocation-time check for the more subtle
cases like bounce buffering due to an incorrect DMA mask.

Furthermore, we can then fix the hackish KConfig dependency so that
architectures without a dma_to_phys() implementation may still
COMPILE_TEST (or even use!) the code. The true dependency is on the
DMA API, so use the appropriate symbol for that.

Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
---
 drivers/iommu/Kconfig          |  3 +--
 drivers/iommu/io-pgtable-arm.c | 24 +++++++++++++-----------
 2 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index 4664c2a..3dc1bcb 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -23,8 +23,7 @@ config IOMMU_IO_PGTABLE
 config IOMMU_IO_PGTABLE_LPAE
 	bool "ARMv7/v8 Long Descriptor Format"
 	select IOMMU_IO_PGTABLE
-	# SWIOTLB guarantees a dma_to_phys() implementation
-	depends on ARM || ARM64 || (COMPILE_TEST && SWIOTLB)
+	depends on HAS_DMA && (ARM || ARM64 || COMPILE_TEST)
 	help
 	  Enable support for the ARM long descriptor pagetable format.
 	  This allocator supports 4K/2M/1G, 16K/32M and 64K/512M page
diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 73c0748..96a4baa 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -202,9 +202,9 @@ typedef u64 arm_lpae_iopte;
 
 static bool selftest_running = false;
 
-static dma_addr_t __arm_lpae_dma_addr(struct device *dev, void *pages)
+static dma_addr_t __arm_lpae_dma_addr(void *pages)
 {
-	return phys_to_dma(dev, virt_to_phys(pages));
+	return (dma_addr_t)virt_to_phys(pages);
 }
 
 static void *__arm_lpae_alloc_pages(size_t size, gfp_t gfp,
@@ -223,10 +223,10 @@ static void *__arm_lpae_alloc_pages(size_t size, gfp_t gfp,
 			goto out_free;
 		/*
 		 * We depend on the IOMMU being able to work with any physical
-		 * address directly, so if the DMA layer suggests it can't by
-		 * giving us back some translation, that bodes very badly...
+		 * address directly, so if the DMA layer suggests otherwise by
+		 * translating or truncating them, that bodes very badly...
 		 */
-		if (dma != __arm_lpae_dma_addr(dev, pages))
+		if (dma != virt_to_phys(pages))
 			goto out_unmap;
 	}
 
@@ -243,10 +243,8 @@ out_free:
 static void __arm_lpae_free_pages(void *pages, size_t size,
 				  struct io_pgtable_cfg *cfg)
 {
-	struct device *dev = cfg->iommu_dev;
-
 	if (!selftest_running)
-		dma_unmap_single(dev, __arm_lpae_dma_addr(dev, pages),
+		dma_unmap_single(cfg->iommu_dev, __arm_lpae_dma_addr(pages),
 				 size, DMA_TO_DEVICE);
 	free_pages_exact(pages, size);
 }
@@ -254,12 +252,11 @@ static void __arm_lpae_free_pages(void *pages, size_t size,
 static void __arm_lpae_set_pte(arm_lpae_iopte *ptep, arm_lpae_iopte pte,
 			       struct io_pgtable_cfg *cfg)
 {
-	struct device *dev = cfg->iommu_dev;
-
 	*ptep = pte;
 
 	if (!selftest_running)
-		dma_sync_single_for_device(dev, __arm_lpae_dma_addr(dev, ptep),
+		dma_sync_single_for_device(cfg->iommu_dev,
+					   __arm_lpae_dma_addr(ptep),
 					   sizeof(pte), DMA_TO_DEVICE);
 }
 
@@ -629,6 +626,11 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg)
 	if (cfg->oas > ARM_LPAE_MAX_ADDR_BITS)
 		return NULL;
 
+	if (cfg->iommu_dev->dma_pfn_offset) {
+		dev_err(cfg->iommu_dev, "Cannot accommodate DMA offset for IOMMU page tables\n");
+		return NULL;
+	}
+
 	data = kmalloc(sizeof(*data), GFP_KERNEL);
 	if (!data)
 		return NULL;
-- 
1.9.1

Re: [PATCH v2] iommu/io-pgtable-arm: Don't use dma_to_phys()

[Yong Wu]

On Thu, 2015-09-17 at 17:42 +0100, Robin Murphy wrote:
> In checking whether DMA addresses differ from physical addresses, using
> dma_to_phys() is actually the wrong thing to do, since it may hide any
> DMA offset, which is precisely one of the things we are checking for.
> Simply casting between the two address types, whilst ugly, is in fact
> the appropriate course of action. Further care (and ugliness) is also
> necessary in the comparison to avoid truncation if phys_addr_t and
> dma_addr_t differ in size.
> 
> We can also reject any device with a fixed DMA offset up-front at page
> table creation, leaving the allocation-time check for the more subtle
> cases like bounce buffering due to an incorrect DMA mask.
> 
> Furthermore, we can then fix the hackish KConfig dependency so that
> architectures without a dma_to_phys() implementation may still
> COMPILE_TEST (or even use!) the code. The true dependency is on the
> DMA API, so use the appropriate symbol for that.
> 
> Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
> ---
[...]
>  
>  static bool selftest_running = false;
>  
> -static dma_addr_t __arm_lpae_dma_addr(struct device *dev, void *pages)
> +static dma_addr_t __arm_lpae_dma_addr(void *pages)
>  {
> -	return phys_to_dma(dev, virt_to_phys(pages));
> +	return (dma_addr_t)virt_to_phys(pages);
>  }
>  
>  static void *__arm_lpae_alloc_pages(size_t size, gfp_t gfp,
> @@ -223,10 +223,10 @@ static void *__arm_lpae_alloc_pages(size_t size, gfp_t gfp,
>  			goto out_free;
>  		/*
>  		 * We depend on the IOMMU being able to work with any physical
> -		 * address directly, so if the DMA layer suggests it can't by
> -		 * giving us back some translation, that bodes very badly...
> +		 * address directly, so if the DMA layer suggests otherwise by
> +		 * translating or truncating them, that bodes very badly...
>  		 */
> -		if (dma != __arm_lpae_dma_addr(dev, pages))
> +		if (dma != virt_to_phys(pages))

Could I ask why not use __arm_lpae_dma_addr(pages) here?
dma is dma_addr_t.

>  			goto out_unmap;
>  	}
>  
> @@ -243,10 +243,8 @@ out_free:
>  static void __arm_lpae_free_pages(void *pages, size_t size,
>  				  struct io_pgtable_cfg *cfg)
>  {
> -	struct device *dev = cfg->iommu_dev;
> -
>  	if (!selftest_running)
> -		dma_unmap_single(dev, __arm_lpae_dma_addr(dev, pages),
> +		dma_unmap_single(cfg->iommu_dev, __arm_lpae_dma_addr(pages),
>  				 size, DMA_TO_DEVICE);
>  	free_pages_exact(pages, size);
>  }
> @@ -254,12 +252,11 @@ static void __arm_lpae_free_pages(void *pages, size_t size,
>  static void __arm_lpae_set_pte(arm_lpae_iopte *ptep, arm_lpae_iopte pte,
>  			       struct io_pgtable_cfg *cfg)
>  {
> -	struct device *dev = cfg->iommu_dev;
> -
>  	*ptep = pte;
>  
>  	if (!selftest_running)
> -		dma_sync_single_for_device(dev, __arm_lpae_dma_addr(dev, ptep),
> +		dma_sync_single_for_device(cfg->iommu_dev,
> +					   __arm_lpae_dma_addr(ptep),
>  					   sizeof(pte), DMA_TO_DEVICE);
>  }
>  
> @@ -629,6 +626,11 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg)
>  	if (cfg->oas > ARM_LPAE_MAX_ADDR_BITS)
>  		return NULL;
>  
> +	if (cfg->iommu_dev->dma_pfn_offset) {
> +		dev_err(cfg->iommu_dev, "Cannot accommodate DMA offset for IOMMU page tables\n");
> +		return NULL;
> +	}
> +
>  	data = kmalloc(sizeof(*data), GFP_KERNEL);
>  	if (!data)
>  		return NULL;

Re: [PATCH v2] iommu/io-pgtable-arm: Don't use dma_to_phys()

[Robin Murphy]

On 18/09/15 09:55, Yong Wu wrote:
> On Thu, 2015-09-17 at 17:42 +0100, Robin Murphy wrote:
[...]
>> the appropriate course of action. Further care (and ugliness) is also
>> necessary in the comparison to avoid truncation if phys_addr_t and
>> dma_addr_t differ in size.
[...]
>>   		/*
>>   		 * We depend on the IOMMU being able to work with any physical
>> -		 * address directly, so if the DMA layer suggests it can't by
>> -		 * giving us back some translation, that bodes very badly...
>> +		 * address directly, so if the DMA layer suggests otherwise by
>> +		 * translating or truncating them, that bodes very badly...
>>   		 */
>> -		if (dma != __arm_lpae_dma_addr(dev, pages))
>> +		if (dma != virt_to_phys(pages))
>
> Could I ask why not use __arm_lpae_dma_addr(pages) here?
> dma is dma_addr_t.

Specifically, the problem case for that is when phys_addr_t is 64-bit 
but dma_addr_t is 32-bit. The cast in __arm_lpae_dma_addr is necessary 
to avoid a truncation warning when we make the DMA API calls, but we 
actually need the opposite in the comparison here - comparing the 
different types directly allows integer promotion to kick in 
appropriately so we don't lose the top half of the larger address. 
Otherwise, you'd never spot the difference between, say, your original 
page at 0x88c0000000 and a bounce-buffered copy that happened to end up 
mapped to 0xc0000000.

Robin.

Re: [PATCH v2] iommu/io-pgtable-arm: Don't use dma_to_phys()

[Russell King - ARM Linux]

On Fri, Sep 18, 2015 at 12:04:26PM +0100, Robin Murphy wrote:
> Specifically, the problem case for that is when phys_addr_t is 64-bit but
> dma_addr_t is 32-bit. The cast in __arm_lpae_dma_addr is necessary to avoid
> a truncation warning when we make the DMA API calls, but we actually need
> the opposite in the comparison here - comparing the different types directly
> allows integer promotion to kick in appropriately so we don't lose the top
> half of the larger address. Otherwise, you'd never spot the difference
> between, say, your original page at 0x88c0000000 and a bounce-buffered copy
> that happened to end up mapped to 0xc0000000.

Hmm.  Thinking about this, I think we ought to add to arch/arm/mm/Kconfig:

 config ARCH_PHYS_ADDR_T_64BIT
 	def_bool ARM_LPAE
 
 config ARCH_DMA_ADDR_T_64BIT
 	bool
+	select ARCH_PHYS_ADDR_T_64BIT

I seem to remember that you're quite right that dma_addr_t <= phys_addr_t
but dma_addr_t must never be bigger than phys_addr_t.

-- 
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

Re: [PATCH v2] iommu/io-pgtable-arm: Don't use dma_to_phys()

[Yong Wu]

On Fri, 2015-09-18 at 12:04 +0100, Robin Murphy wrote:
> On 18/09/15 09:55, Yong Wu wrote:
> > On Thu, 2015-09-17 at 17:42 +0100, Robin Murphy wrote:
> [...]
> >> the appropriate course of action. Further care (and ugliness) is also
> >> necessary in the comparison to avoid truncation if phys_addr_t and
> >> dma_addr_t differ in size.
> [...]
> >>   		/*
> >>   		 * We depend on the IOMMU being able to work with any physical
> >> -		 * address directly, so if the DMA layer suggests it can't by
> >> -		 * giving us back some translation, that bodes very badly...
> >> +		 * address directly, so if the DMA layer suggests otherwise by
> >> +		 * translating or truncating them, that bodes very badly...
> >>   		 */
> >> -		if (dma != __arm_lpae_dma_addr(dev, pages))
> >> +		if (dma != virt_to_phys(pages))
> >
> > Could I ask why not use __arm_lpae_dma_addr(pages) here?
> > dma is dma_addr_t.
> 
> Specifically, the problem case for that is when phys_addr_t is 64-bit 
> but dma_addr_t is 32-bit. The cast in __arm_lpae_dma_addr is necessary 
> to avoid a truncation warning when we make the DMA API calls, but we 
> actually need the opposite in the comparison here - comparing the 
> different types directly allows integer promotion to kick in 
> appropriately so we don't lose the top half of the larger address. 
> Otherwise, you'd never spot the difference between, say, your original 
> page at 0x88c0000000 and a bounce-buffered copy that happened to end up 
> mapped to 0xc0000000.

Thanks.

About here:
> @@ -629,6 +626,11 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg
*cfg)
>       if (cfg->oas > ARM_LPAE_MAX_ADDR_BITS)
>               return NULL;
>  
> +     if (cfg->iommu_dev->dma_pfn_offset) {

Do we need change to :
	if (!selftest_running && cfg->iommu_dev->dma_pfn_offset) {

cfg->iommu_dev will be null while self test.

> +             dev_err(cfg->iommu_dev, "Cannot accommodate DMA offset
for IOMMU page tables\n");
> +             return NULL;
> +     }
> +
>       data = kmalloc(sizeof(*data), GFP_KERNEL);
>       if (!data)
>               return NULL;

> 
> Robin.
> 

Re: [PATCH v2] iommu/io-pgtable-arm: Don't use dma_to_phys()

[Robin Murphy]

On 22/09/15 14:25, Yong Wu wrote:
[...]
> About here:
>> @@ -629,6 +626,11 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg
> *cfg)
>>        if (cfg->oas > ARM_LPAE_MAX_ADDR_BITS)
>>                return NULL;
>>   
>> +     if (cfg->iommu_dev->dma_pfn_offset) {
> 
> Do we need change to :
> 	if (!selftest_running && cfg->iommu_dev->dma_pfn_offset) {
> 
> cfg->iommu_dev will be null while self test.

Urgh, you're absolutely right. Must have been one of those days when I
had loads of noisy debug in there and turned the self-tests off :(

Will; since the branch hasn't gone anywhere yet, are you OK to take the below?

Robin.

----->8-----
From: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
Date: Tue, 22 Sep 2015 14:52:27 +0100
Subject: [PATCH] fixup! iommu/io-pgtable-arm: Don't use dma_to_phys()

Signed-off-by: Robin Murphy <robin.murphy-5wv7dgnIgG8@public.gmane.org>
---
 drivers/iommu/io-pgtable-arm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 1f08ce7..2ba2323 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -628,7 +628,7 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg *cfg)
        if (cfg->oas > ARM_LPAE_MAX_ADDR_BITS)
                return NULL;
 
-       if (cfg->iommu_dev->dma_pfn_offset) {
+       if (!selftest_running && cfg->iommu_dev->dma_pfn_offset) {
                dev_err(cfg->iommu_dev, "Cannot accommodate DMA offset for IOMMU page tables\n");
                return NULL;
        }

Re: [PATCH v2] iommu/io-pgtable-arm: Don't use dma_to_phys()

[Will Deacon]

On Tue, Sep 22, 2015 at 05:23:16PM +0100, Robin Murphy wrote:
> On 22/09/15 14:25, Yong Wu wrote:
> [...]
> > About here:
> >> @@ -629,6 +626,11 @@ arm_lpae_alloc_pgtable(struct io_pgtable_cfg
> > *cfg)
> >>        if (cfg->oas > ARM_LPAE_MAX_ADDR_BITS)
> >>                return NULL;
> >>   
> >> +     if (cfg->iommu_dev->dma_pfn_offset) {
> > 
> > Do we need change to :
> > 	if (!selftest_running && cfg->iommu_dev->dma_pfn_offset) {
> > 
> > cfg->iommu_dev will be null while self test.
> 
> Urgh, you're absolutely right. Must have been one of those days when I
> had loads of noisy debug in there and turned the self-tests off :(
> 
> Will; since the branch hasn't gone anywhere yet, are you OK to take the below?

Yeah, no problem. I'll fold it in when I get a chance.

Will