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[PATCH] sparc: iommu/pci_sun4v: fix page alignment in dma mapping

stian@itx.no posted 1 patch 1 month, 2 weeks ago 
arch/sparc/kernel/iommu.c     | 2 ++
arch/sparc/kernel/pci_sun4v.c | 2 +-
2 files changed, 3 insertions(+), 1 deletion(-)
[PATCH] sparc: iommu/pci_sun4v: fix page alignment in dma mapping
Posted by stian@itx.no 1 month, 2 weeks ago 
From: Stian Halseth <stian@itx.no>

'phys' may include an offset within the page, while 'base_paddr' is already page-aligned.

This caused incorrect DMA mapping in dma_4u_map_phys and dma_4v_map_phys.

Fix both functions by masking phys with IO_PAGE_MASK or subtracting the page offset.

Fixes: 38c0d0ebf520 ("sparc: Use physical address DMA mapping")

Reported-by: Stian Halseth <stian@itx.no>
Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Stian Halseth <stian@itx.no>
---
 arch/sparc/kernel/iommu.c     | 2 ++
 arch/sparc/kernel/pci_sun4v.c | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/sparc/kernel/iommu.c b/arch/sparc/kernel/iommu.c
index 46ef88bc9c26..f3755a388ac7 100644
--- a/arch/sparc/kernel/iommu.c
+++ b/arch/sparc/kernel/iommu.c
@@ -312,6 +312,8 @@ static dma_addr_t dma_4u_map_phys(struct device *dev, phys_addr_t phys,
 	if (direction != DMA_TO_DEVICE)
 		iopte_protection |= IOPTE_WRITE;
 
+	phys -= offset_in_page(phys);
+
 	for (i = 0; i < npages; i++, base++, phys += IO_PAGE_SIZE)
 		iopte_val(*base) = iopte_protection | phys;
 
diff --git a/arch/sparc/kernel/pci_sun4v.c b/arch/sparc/kernel/pci_sun4v.c
index 791f0a76665f..2f30eeac4861 100644
--- a/arch/sparc/kernel/pci_sun4v.c
+++ b/arch/sparc/kernel/pci_sun4v.c
@@ -411,7 +411,7 @@ static dma_addr_t dma_4v_map_phys(struct device *dev, phys_addr_t phys,
 	iommu_batch_start(dev, prot, entry);
 
 	for (i = 0; i < npages; i++, phys += IO_PAGE_SIZE) {
-		long err = iommu_batch_add(phys, mask);
+		long err = iommu_batch_add(phys & IO_PAGE_MASK, mask);
 		if (unlikely(err < 0L))
 			goto iommu_map_fail;
 	}
-- 
2.53.0
Re: [PATCH] sparc: iommu/pci_sun4v: fix page alignment in dma mapping
Posted by John Paul Adrian Glaubitz 1 month, 2 weeks ago 
Hi Stian,

please rephrase the subject to:

	sparc: Fix page alignment in dma mapping

Your patch is not specific to sun4v but also fixes generic sparc code,
so you should remove the part "iommu/pci_sun4v:" from the subject.

On Tue, 2026-02-17 at 17:21 +0100, stian@itx.no wrote:
> From: Stian Halseth <stian@itx.no>
> 
> 'phys' may include an offset within the page, while 'base_paddr' is already page-aligned.
> 
> This caused incorrect DMA mapping in dma_4u_map_phys and dma_4v_map_phys.
> 
> Fix both functions by masking phys with IO_PAGE_MASK or subtracting the page offset.

Please remove the newlines between your sentences, they're not necessary
and also trim the lines at 80 columns.

> Fixes: 38c0d0ebf520 ("sparc: Use physical address DMA mapping")
> 
> Reported-by: Stian Halseth <stian@itx.no>
> Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Stian Halseth <stian@itx.no>
> ---
>  arch/sparc/kernel/iommu.c     | 2 ++
>  arch/sparc/kernel/pci_sun4v.c | 2 +-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/sparc/kernel/iommu.c b/arch/sparc/kernel/iommu.c
> index 46ef88bc9c26..f3755a388ac7 100644
> --- a/arch/sparc/kernel/iommu.c
> +++ b/arch/sparc/kernel/iommu.c
> @@ -312,6 +312,8 @@ static dma_addr_t dma_4u_map_phys(struct device *dev, phys_addr_t phys,
>  	if (direction != DMA_TO_DEVICE)
>  		iopte_protection |= IOPTE_WRITE;
>  
> +	phys -= offset_in_page(phys);
> +
>  	for (i = 0; i < npages; i++, base++, phys += IO_PAGE_SIZE)
>  		iopte_val(*base) = iopte_protection | phys;
>  
> diff --git a/arch/sparc/kernel/pci_sun4v.c b/arch/sparc/kernel/pci_sun4v.c
> index 791f0a76665f..2f30eeac4861 100644
> --- a/arch/sparc/kernel/pci_sun4v.c
> +++ b/arch/sparc/kernel/pci_sun4v.c
> @@ -411,7 +411,7 @@ static dma_addr_t dma_4v_map_phys(struct device *dev, phys_addr_t phys,
>  	iommu_batch_start(dev, prot, entry);
>  
>  	for (i = 0; i < npages; i++, phys += IO_PAGE_SIZE) {
> -		long err = iommu_batch_add(phys, mask);
> +		long err = iommu_batch_add(phys & IO_PAGE_MASK, mask);
>  		if (unlikely(err < 0L))
>  			goto iommu_map_fail;
>  	}

Looks good to me otherwise.

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913
Re: [PATCH] sparc: iommu/pci_sun4v: fix page alignment in dma mapping
Posted by Stian Halseth 1 month, 2 weeks ago 
Hi Adrian,

Thanks for the review and suggestions.

On Tue, 2026-02-17 at 17:38 +0100, John Paul Adrian Glaubitz wrote:
> Hi Stian,
> 
> please rephrase the subject to:
> 
>  sparc: Fix page alignment in dma mapping
> 
> Your patch is not specific to sun4v but also fixes generic sparc
> code,
> so you should remove the part "iommu/pci_sun4v:" from the subject.
> 
Understood — I will update the patch subject as suggested.
> On Tue, 2026-02-17 at 17:21 +0100, stian@itx.no wrote:
> > From: Stian Halseth <stian@itx.no>
> > 
> > 'phys' may include an offset within the page, while 'base_paddr' is
> > already page-aligned.
> > 
> > This caused incorrect DMA mapping in dma_4u_map_phys and
> > dma_4v_map_phys.
> > 
> > Fix both functions by masking phys with IO_PAGE_MASK or subtracting
> > the page offset.
> 
> Please remove the newlines between your sentences, they're not
> necessary
> and also trim the lines at 80 columns.

Will do — I’ll reformat the commit message to 80-column lines
and remove extra newlines.

> > Fixes: 38c0d0ebf520 ("sparc: Use physical address DMA mapping")
> > 
> > Reported-by: Stian Halseth <stian@itx.no>
> > Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > Signed-off-by: Stian Halseth <stian@itx.no>
> > ---
> >  arch/sparc/kernel/iommu.c     | 2 ++
> >  arch/sparc/kernel/pci_sun4v.c | 2 +-
> >  2 files changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/sparc/kernel/iommu.c b/arch/sparc/kernel/iommu.c
> > index 46ef88bc9c26..f3755a388ac7 100644
> > --- a/arch/sparc/kernel/iommu.c
> > +++ b/arch/sparc/kernel/iommu.c
> > @@ -312,6 +312,8 @@ static dma_addr_t dma_4u_map_phys(struct device
> > *dev, phys_addr_t phys,
> >   if (direction != DMA_TO_DEVICE)
> >   iopte_protection |= IOPTE_WRITE;
> >  
> > + phys -= offset_in_page(phys);
> > +
> >   for (i = 0; i < npages; i++, base++, phys += IO_PAGE_SIZE)
> >   iopte_val(*base) = iopte_protection | phys;
> >  
> > diff --git a/arch/sparc/kernel/pci_sun4v.c
> > b/arch/sparc/kernel/pci_sun4v.c
> > index 791f0a76665f..2f30eeac4861 100644
> > --- a/arch/sparc/kernel/pci_sun4v.c
> > +++ b/arch/sparc/kernel/pci_sun4v.c
> > @@ -411,7 +411,7 @@ static dma_addr_t dma_4v_map_phys(struct device
> > *dev, phys_addr_t phys,
> >   iommu_batch_start(dev, prot, entry);
> >  
> >   for (i = 0; i < npages; i++, phys += IO_PAGE_SIZE) {
> > - long err = iommu_batch_add(phys, mask);
> > + long err = iommu_batch_add(phys & IO_PAGE_MASK, mask);
> >   if (unlikely(err < 0L))
> >   goto iommu_map_fail;
> >   }
> 
> Looks good to me otherwise.
> 
> Adrian
> 

I’ll send an updated patch (v2) shortly with these changes applied.

Thanks again for reviewing.

-- 
Med vennlig hilsen
Stian Halseth​​
Re: [PATCH] sparc: iommu/pci_sun4v: fix page alignment in dma mapping
Posted by John Paul Adrian Glaubitz 1 month, 2 weeks ago 
Hi Stian,

On Tue, 2026-02-17 at 17:48 +0100, Stian Halseth wrote:
> Thanks for the review and suggestions.
> 
> On Tue, 2026-02-17 at 17:38 +0100, John Paul Adrian Glaubitz wrote:
> > Hi Stian,
> > 
> > please rephrase the subject to:
> > 
> >  sparc: Fix page alignment in dma mapping
> > 
> > Your patch is not specific to sun4v but also fixes generic sparc
> > code,
> > so you should remove the part "iommu/pci_sun4v:" from the subject.
> > 
> Understood — I will update the patch subject as suggested.
> > On Tue, 2026-02-17 at 17:21 +0100, stian@itx.no wrote:
> > > From: Stian Halseth <stian@itx.no>
> > > 
> > > 'phys' may include an offset within the page, while 'base_paddr' is
> > > already page-aligned.
> > > 
> > > This caused incorrect DMA mapping in dma_4u_map_phys and
> > > dma_4v_map_phys.
> > > 
> > > Fix both functions by masking phys with IO_PAGE_MASK or subtracting
> > > the page offset.
> > 
> > Please remove the newlines between your sentences, they're not
> > necessary
> > and also trim the lines at 80 columns.
> 
> Will do — I’ll reformat the commit message to 80-column lines
> and remove extra newlines.

Perfect! I have nothing to add. Let's have Andreas review your patch ;-).

Adrian

-- 
 .''`.  John Paul Adrian Glaubitz
: :' :  Debian Developer
`. `'   Physicist
  `-    GPG: 62FF 8A75 84E0 2956 9546  0006 7426 3B37 F5B5 F913
[PATCH v2] sparc: Fix page alignment in dma mapping
Posted by stian@itx.no 1 month, 2 weeks ago 
From: Stian Halseth <stian@itx.no>

'phys' may include an offset within the page, while 'base_paddr' is already
page-aligned. This caused incorrect DMA mapping in dma_4u_map_phys and
dma_4v_map_phys.

Fix both functions by masking phys with IO_PAGE_MASK or subtracting the
page offset, covering both generic SPARC code and sun4v.

Fixes: 38c0d0ebf520 ("sparc: Use physical address DMA mapping")
Reported-by: Stian Halseth <stian@itx.no>
Closes: https://github.com/sparclinux/issues/issues/75
Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Stian Halseth <stian@itx.no>
---
 arch/sparc/kernel/iommu.c     | 2 ++
 arch/sparc/kernel/pci_sun4v.c | 2 +-
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/sparc/kernel/iommu.c b/arch/sparc/kernel/iommu.c
index 46ef88bc9c26..f3755a388ac7 100644
--- a/arch/sparc/kernel/iommu.c
+++ b/arch/sparc/kernel/iommu.c
@@ -312,6 +312,8 @@ static dma_addr_t dma_4u_map_phys(struct device *dev, phys_addr_t phys,
 	if (direction != DMA_TO_DEVICE)
 		iopte_protection |= IOPTE_WRITE;
 
+	phys -= offset_in_page(phys);
+
 	for (i = 0; i < npages; i++, base++, phys += IO_PAGE_SIZE)
 		iopte_val(*base) = iopte_protection | phys;
 
diff --git a/arch/sparc/kernel/pci_sun4v.c b/arch/sparc/kernel/pci_sun4v.c
index 791f0a76665f..2f30eeac4861 100644
--- a/arch/sparc/kernel/pci_sun4v.c
+++ b/arch/sparc/kernel/pci_sun4v.c
@@ -411,7 +411,7 @@ static dma_addr_t dma_4v_map_phys(struct device *dev, phys_addr_t phys,
 	iommu_batch_start(dev, prot, entry);
 
 	for (i = 0; i < npages; i++, phys += IO_PAGE_SIZE) {
-		long err = iommu_batch_add(phys, mask);
+		long err = iommu_batch_add(phys & IO_PAGE_MASK, mask);
 		if (unlikely(err < 0L))
 			goto iommu_map_fail;
 	}
-- 
2.53.0
Re: [PATCH v2] sparc: Fix page alignment in dma mapping
Posted by Leon Romanovsky 1 month, 1 week ago 
On Tue, Feb 17, 2026 at 06:10:19PM +0100, stian@itx.no wrote:
> From: Stian Halseth <stian@itx.no>
> 
> 'phys' may include an offset within the page, while 'base_paddr' is already
> page-aligned. This caused incorrect DMA mapping in dma_4u_map_phys and
> dma_4v_map_phys.
> 
> Fix both functions by masking phys with IO_PAGE_MASK or subtracting the
> page offset, covering both generic SPARC code and sun4v.
> 
> Fixes: 38c0d0ebf520 ("sparc: Use physical address DMA mapping")
> Reported-by: Stian Halseth <stian@itx.no>
> Closes: https://github.com/sparclinux/issues/issues/75
> Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Stian Halseth <stian@itx.no>
> ---
>  arch/sparc/kernel/iommu.c     | 2 ++
>  arch/sparc/kernel/pci_sun4v.c | 2 +-
>  2 files changed, 3 insertions(+), 1 deletion(-)
> 

Thanks,
Reviewed-by: Leon Romanovsky <leon@kernel.org>
Re: [PATCH v2] sparc: Fix page alignment in dma mapping
Posted by Marek Szyprowski 1 month, 1 week ago 
On 17.02.2026 18:10, stian@itx.no wrote:
> From: Stian Halseth <stian@itx.no>
>
> 'phys' may include an offset within the page, while 'base_paddr' is already
> page-aligned. This caused incorrect DMA mapping in dma_4u_map_phys and
> dma_4v_map_phys.
>
> Fix both functions by masking phys with IO_PAGE_MASK or subtracting the
> page offset, covering both generic SPARC code and sun4v.
>
> Fixes: 38c0d0ebf520 ("sparc: Use physical address DMA mapping")
> Reported-by: Stian Halseth <stian@itx.no>
> Closes: https://protect2.fireeye.com/v1/url?k=4d8fbc00-1214850c-4d8e374f-000babff3563-ee1be24be576e072&q=1&e=0f8967ce-f558-4339-bddb-f324ec46c035&u=https%3A%2F%2Fgithub.com%2Fsparclinux%2Fissues%2Fissues%2F75
> Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> Signed-off-by: Stian Halseth <stian@itx.no>
> ---
>   arch/sparc/kernel/iommu.c     | 2 ++
>   arch/sparc/kernel/pci_sun4v.c | 2 +-
>   2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/sparc/kernel/iommu.c b/arch/sparc/kernel/iommu.c
> index 46ef88bc9c26..f3755a388ac7 100644
> --- a/arch/sparc/kernel/iommu.c
> +++ b/arch/sparc/kernel/iommu.c
> @@ -312,6 +312,8 @@ static dma_addr_t dma_4u_map_phys(struct device *dev, phys_addr_t phys,
>   	if (direction != DMA_TO_DEVICE)
>   		iopte_protection |= IOPTE_WRITE;
>   
> +	phys -= offset_in_page(phys);
> +

I've just noticed that IO_PAGE_SIZE might not equal to PAGE_SIZE (not 
sure if this is true in case of SPARCs), so it would be better to rely 
on IO_PAGE_MASK or IO_PAGE_SIZE only. Just unify the fix for the both 
affected functions either by masking phys with IO_PAGE_SIZE where it is 
used or by subtracting (phys & ~IO_PAGE_MASK) from it.

>   	for (i = 0; i < npages; i++, base++, phys += IO_PAGE_SIZE)
>   		iopte_val(*base) = iopte_protection | phys;
>   
> diff --git a/arch/sparc/kernel/pci_sun4v.c b/arch/sparc/kernel/pci_sun4v.c
> index 791f0a76665f..2f30eeac4861 100644
> --- a/arch/sparc/kernel/pci_sun4v.c
> +++ b/arch/sparc/kernel/pci_sun4v.c
> @@ -411,7 +411,7 @@ static dma_addr_t dma_4v_map_phys(struct device *dev, phys_addr_t phys,
>   	iommu_batch_start(dev, prot, entry);
>   
>   	for (i = 0; i < npages; i++, phys += IO_PAGE_SIZE) {
> -		long err = iommu_batch_add(phys, mask);
> +		long err = iommu_batch_add(phys & IO_PAGE_MASK, mask);
>   		if (unlikely(err < 0L))
>   			goto iommu_map_fail;
>   	}

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland
Re: [PATCH v2] sparc: Fix page alignment in dma mapping
Posted by Stian Halseth 1 month, 1 week ago 
On Wed, 2026-02-18 at 11:28 +0100, Marek Szyprowski wrote:
> On 17.02.2026 18:10, stian@itx.no wrote:
> > From: Stian Halseth <stian@itx.no>
> > 
> > 'phys' may include an offset within the page, while 'base_paddr' is
> > already
> > page-aligned. This caused incorrect DMA mapping in dma_4u_map_phys
> > and
> > dma_4v_map_phys.
> > 
> > Fix both functions by masking phys with IO_PAGE_MASK or subtracting
> > the
> > page offset, covering both generic SPARC code and sun4v.
> > 
> > Fixes: 38c0d0ebf520 ("sparc: Use physical address DMA mapping")
> > Reported-by: Stian Halseth <stian@itx.no>
> > Closes: https://protect2.fireeye.com/v1/url?k=4d8fbc00-1214850c-
> > 4d8e374f-000babff3563-ee1be24be576e072&q=1&e=0f8967ce-f558-4339-
> > bddb-
> > f324ec46c035&u=https%3A%2F%2Fgithub.com%2Fsparclinux%2Fissues%2Fiss
> > ues%2F75
> > Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > Signed-off-by: Stian Halseth <stian@itx.no>
> > ---
> >   arch/sparc/kernel/iommu.c     | 2 ++
> >   arch/sparc/kernel/pci_sun4v.c | 2 +-
> >   2 files changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/sparc/kernel/iommu.c b/arch/sparc/kernel/iommu.c
> > index 46ef88bc9c26..f3755a388ac7 100644
> > --- a/arch/sparc/kernel/iommu.c
> > +++ b/arch/sparc/kernel/iommu.c
> > @@ -312,6 +312,8 @@ static dma_addr_t dma_4u_map_phys(struct device
> > *dev, phys_addr_t phys,
> >    if (direction != DMA_TO_DEVICE)
> >    iopte_protection |= IOPTE_WRITE;
> >   
> > + phys -= offset_in_page(phys);
> > +
> 
> I've just noticed that IO_PAGE_SIZE might not equal to PAGE_SIZE (not
> sure if this is true in case of SPARCs), so it would be better to
> rely 
> on IO_PAGE_MASK or IO_PAGE_SIZE only. Just unify the fix for the both
> affected functions either by masking phys with IO_PAGE_SIZE where it
> is 
> used or by subtracting (phys & ~IO_PAGE_MASK) from it.
> 

Good point, and thanks for the review.

I failed to consider that the offset_in_page is based on PAGE_SIZE, not
IO_PAGE_SIZE.

Suggestion, subtract IO_PAGE_MASK in both functions.

arch/sparc/kernel/iommu.c:
 -phys -= offset_in_page(phys)
 +phys &= IO_PAGE_MASK;


arch/sparc/kernel/pci_sun4v.c (better to subtract before loop?):
 +phys &= IO_PAGE_MASK;

 for (i = 0; i < npages; i++, phys += IO_PAGE_SIZE) {
         -long err = iommu_batch_add(phys & IO_PAGE_MASK, mask);
         +long err = iommu_batch_add(phys, mask);
         if (unlikely(err < 0L))
                 goto iommu_map_fail;
 }

Is this acceptable, and in line with kernel coding style?

If yes, I can submit patch v3 with this proposed change.

And Patch v3, should be sent using the message ID of this review
response, right? Still learning :)



> >    for (i = 0; i < npages; i++, base++, phys += IO_PAGE_SIZE)
> >    iopte_val(*base) = iopte_protection | phys;
> >   
> > diff --git a/arch/sparc/kernel/pci_sun4v.c
> > b/arch/sparc/kernel/pci_sun4v.c
> > index 791f0a76665f..2f30eeac4861 100644
> > --- a/arch/sparc/kernel/pci_sun4v.c
> > +++ b/arch/sparc/kernel/pci_sun4v.c
> > @@ -411,7 +411,7 @@ static dma_addr_t dma_4v_map_phys(struct device
> > *dev, phys_addr_t phys,
> >    iommu_batch_start(dev, prot, entry);
> >   
> >    for (i = 0; i < npages; i++, phys += IO_PAGE_SIZE) {
> > - long err = iommu_batch_add(phys, mask);
> > + long err = iommu_batch_add(phys & IO_PAGE_MASK, mask);
> >    if (unlikely(err < 0L))
> >    goto iommu_map_fail;
> >    }
> 
> Best regards

-- 
Med vennlig hilsen
Stian Halseth
Mobile       +47 406 77 777
Office(dir) +47 236 80 400 (402)
E-mail          stian@itx.no
​​
Re: [PATCH v2] sparc: Fix page alignment in dma mapping
Posted by Leon Romanovsky 1 month, 1 week ago 
On Wed, Feb 18, 2026 at 12:09:06PM +0100, Stian Halseth wrote:
> On Wed, 2026-02-18 at 11:28 +0100, Marek Szyprowski wrote:
> > On 17.02.2026 18:10, stian@itx.no wrote:
> > > From: Stian Halseth <stian@itx.no>
> > > 
> > > 'phys' may include an offset within the page, while 'base_paddr' is
> > > already
> > > page-aligned. This caused incorrect DMA mapping in dma_4u_map_phys
> > > and
> > > dma_4v_map_phys.
> > > 
> > > Fix both functions by masking phys with IO_PAGE_MASK or subtracting
> > > the
> > > page offset, covering both generic SPARC code and sun4v.
> > > 
> > > Fixes: 38c0d0ebf520 ("sparc: Use physical address DMA mapping")
> > > Reported-by: Stian Halseth <stian@itx.no>
> > > Closes: https://protect2.fireeye.com/v1/url?k=4d8fbc00-1214850c-
> > > 4d8e374f-000babff3563-ee1be24be576e072&q=1&e=0f8967ce-f558-4339-
> > > bddb-
> > > f324ec46c035&u=https%3A%2F%2Fgithub.com%2Fsparclinux%2Fissues%2Fiss
> > > ues%2F75
> > > Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
> > > Signed-off-by: Stian Halseth <stian@itx.no>
> > > ---
> > >   arch/sparc/kernel/iommu.c     | 2 ++
> > >   arch/sparc/kernel/pci_sun4v.c | 2 +-
> > >   2 files changed, 3 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/sparc/kernel/iommu.c b/arch/sparc/kernel/iommu.c
> > > index 46ef88bc9c26..f3755a388ac7 100644
> > > --- a/arch/sparc/kernel/iommu.c
> > > +++ b/arch/sparc/kernel/iommu.c
> > > @@ -312,6 +312,8 @@ static dma_addr_t dma_4u_map_phys(struct device
> > > *dev, phys_addr_t phys,
> > >    if (direction != DMA_TO_DEVICE)
> > >    iopte_protection |= IOPTE_WRITE;
> > >   
> > > + phys -= offset_in_page(phys);
> > > +
> > 
> > I've just noticed that IO_PAGE_SIZE might not equal to PAGE_SIZE (not
> > sure if this is true in case of SPARCs), so it would be better to
> > rely 
> > on IO_PAGE_MASK or IO_PAGE_SIZE only. Just unify the fix for the both
> > affected functions either by masking phys with IO_PAGE_SIZE where it
> > is 
> > used or by subtracting (phys & ~IO_PAGE_MASK) from it.
> > 
> 
> Good point, and thanks for the review.
> 
> I failed to consider that the offset_in_page is based on PAGE_SIZE, not
> IO_PAGE_SIZE.
> 
> Suggestion, subtract IO_PAGE_MASK in both functions.
> 
> arch/sparc/kernel/iommu.c:
>  -phys -= offset_in_page(phys)
>  +phys &= IO_PAGE_MASK;
> 
> 
> arch/sparc/kernel/pci_sun4v.c (better to subtract before loop?):
>  +phys &= IO_PAGE_MASK;
> 
>  for (i = 0; i < npages; i++, phys += IO_PAGE_SIZE) {
>          -long err = iommu_batch_add(phys & IO_PAGE_MASK, mask);
>          +long err = iommu_batch_add(phys, mask);
>          if (unlikely(err < 0L))
>                  goto iommu_map_fail;
>  }
> 
> Is this acceptable, and in line with kernel coding style?
> 
> If yes, I can submit patch v3 with this proposed change.
> 
> And Patch v3, should be sent using the message ID of this review
> response, right? Still learning :)

No, just send patch v3 without Reply-To field. Add changelog under ---
trailer line and describe changes.

Thanks
Re: [PATCH v2] sparc: Fix page alignment in dma mapping
Posted by Marek Szyprowski 1 month, 1 week ago 
On 18.02.2026 12:09, Stian Halseth wrote:
> On Wed, 2026-02-18 at 11:28 +0100, Marek Szyprowski wrote:
>> On 17.02.2026 18:10, stian@itx.no wrote:
>>> From: Stian Halseth <stian@itx.no>
>>>
>>> 'phys' may include an offset within the page, while 'base_paddr' is
>>> already
>>> page-aligned. This caused incorrect DMA mapping in dma_4u_map_phys
>>> and
>>> dma_4v_map_phys.
>>>
>>> Fix both functions by masking phys with IO_PAGE_MASK or subtracting
>>> the
>>> page offset, covering both generic SPARC code and sun4v.
>>>
>>> Fixes: 38c0d0ebf520 ("sparc: Use physical address DMA mapping")
>>> Reported-by: Stian Halseth <stian@itx.no>
>>> Closes: https://protect2.fireeye.com/v1/url?k=4d8fbc00-1214850c-
>>> 4d8e374f-000babff3563-ee1be24be576e072&q=1&e=0f8967ce-f558-4339-
>>> bddb-
>>> f324ec46c035&u=https%3A%2F%2Fgithub.com%2Fsparclinux%2Fissues%2Fiss
>>> ues%2F75
>>> Suggested-by: Marek Szyprowski <m.szyprowski@samsung.com>
>>> Signed-off-by: Stian Halseth <stian@itx.no>
>>> ---
>>>    arch/sparc/kernel/iommu.c     | 2 ++
>>>    arch/sparc/kernel/pci_sun4v.c | 2 +-
>>>    2 files changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/arch/sparc/kernel/iommu.c b/arch/sparc/kernel/iommu.c
>>> index 46ef88bc9c26..f3755a388ac7 100644
>>> --- a/arch/sparc/kernel/iommu.c
>>> +++ b/arch/sparc/kernel/iommu.c
>>> @@ -312,6 +312,8 @@ static dma_addr_t dma_4u_map_phys(struct device
>>> *dev, phys_addr_t phys,
>>>     if (direction != DMA_TO_DEVICE)
>>>     iopte_protection |= IOPTE_WRITE;
>>>    
>>> + phys -= offset_in_page(phys);
>>> +
>> I've just noticed that IO_PAGE_SIZE might not equal to PAGE_SIZE (not
>> sure if this is true in case of SPARCs), so it would be better to
>> rely
>> on IO_PAGE_MASK or IO_PAGE_SIZE only. Just unify the fix for the both
>> affected functions either by masking phys with IO_PAGE_SIZE where it
>> is
>> used or by subtracting (phys & ~IO_PAGE_MASK) from it.
>>
> Good point, and thanks for the review.
>
> I failed to consider that the offset_in_page is based on PAGE_SIZE, not
> IO_PAGE_SIZE.
>
> Suggestion, subtract IO_PAGE_MASK in both functions.
>
> arch/sparc/kernel/iommu.c:
>   -phys -= offset_in_page(phys)
>   +phys &= IO_PAGE_MASK;
>
>
> arch/sparc/kernel/pci_sun4v.c (better to subtract before loop?):
>   +phys &= IO_PAGE_MASK;
>
>   for (i = 0; i < npages; i++, phys += IO_PAGE_SIZE) {
>           -long err = iommu_batch_add(phys & IO_PAGE_MASK, mask);
>           +long err = iommu_batch_add(phys, mask);
>           if (unlikely(err < 0L))
>                   goto iommu_map_fail;
>   }
>
> Is this acceptable, and in line with kernel coding style?

Yes, that's fine.

> If yes, I can submit patch v3 with this proposed change.
>
> And Patch v3, should be sent using the message ID of this review
> response, right? Still learning :)

Usually the next version is being sent as a new thread. Just add a few 
lines of history and links to the previous attempt(s) to it, like for 
example here: 
https://lore.kernel.org/all/20260203102133.1478331-1-m.szyprowski@samsung.com/

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

Patchew 2.1-devel-ea86937

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