[v2] dma-mapping: use vmalloc_to_page for vmalloc addresses

[PATCH v2] dma-mapping: use vmalloc_to_page for vmalloc addresses

Posted by Roman Skakun 2 years, 10 months ago

This commit is dedicated to fix incorrect conversion from
cpu_addr to page address in cases when we get virtual
address which allocated in the vmalloc range.
As the result, virt_to_page() cannot convert this address
properly and return incorrect page address.

Need to detect such cases and obtains the page address using
vmalloc_to_page() instead.

Signed-off-by: Roman Skakun <roman_skakun@epam.com>
Reviewed-by: Andrii Anisov <andrii_anisov@epam.com>
---
Hey!
Thanks for suggestions, Christoph!
I updated the patch according to your advice.
But, I'm so surprised because nobody catches this problem
in the common code before. It looks a bit strange as for me. 


 kernel/dma/ops_helpers.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/ops_helpers.c b/kernel/dma/ops_helpers.c
index 910ae69cae77..782728d8a393 100644
--- a/kernel/dma/ops_helpers.c
+++ b/kernel/dma/ops_helpers.c
@@ -5,6 +5,14 @@
  */
 #include <linux/dma-map-ops.h>
 
+static struct page *cpu_addr_to_page(void *cpu_addr)
+{
+	if (is_vmalloc_addr(cpu_addr))
+		return vmalloc_to_page(cpu_addr);
+	else
+		return virt_to_page(cpu_addr);
+}
+
 /*
  * Create scatter-list for the already allocated DMA buffer.
  */
@@ -12,7 +20,7 @@ int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
 		 void *cpu_addr, dma_addr_t dma_addr, size_t size,
 		 unsigned long attrs)
 {
-	struct page *page = virt_to_page(cpu_addr);
+	struct page *page = cpu_addr_to_page(cpu_addr);
 	int ret;
 
 	ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
@@ -43,7 +51,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 		return -ENXIO;
 
 	return remap_pfn_range(vma, vma->vm_start,
-			page_to_pfn(virt_to_page(cpu_addr)) + vma->vm_pgoff,
+			page_to_pfn(cpu_addr_to_page(cpu_addr)) + vma->vm_pgoff,
 			user_count << PAGE_SHIFT, vma->vm_page_prot);
 #else
 	return -ENXIO;
-- 
2.25.1

Re: [PATCH v2] dma-mapping: use vmalloc_to_page for vmalloc addresses

Posted by Stefano Stabellini 2 years, 9 months ago

On Tue, 22 Jun 2021, Roman Skakun wrote:
> This commit is dedicated to fix incorrect conversion from
> cpu_addr to page address in cases when we get virtual
> address which allocated in the vmalloc range.
> As the result, virt_to_page() cannot convert this address
> properly and return incorrect page address.
> 
> Need to detect such cases and obtains the page address using
> vmalloc_to_page() instead.
> 
> Signed-off-by: Roman Skakun <roman_skakun@epam.com>
> Reviewed-by: Andrii Anisov <andrii_anisov@epam.com>
> ---
> Hey!
> Thanks for suggestions, Christoph!
> I updated the patch according to your advice.
> But, I'm so surprised because nobody catches this problem
> in the common code before. It looks a bit strange as for me. 
> 
> 
>  kernel/dma/ops_helpers.c | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/dma/ops_helpers.c b/kernel/dma/ops_helpers.c
> index 910ae69cae77..782728d8a393 100644
> --- a/kernel/dma/ops_helpers.c
> +++ b/kernel/dma/ops_helpers.c
> @@ -5,6 +5,14 @@
>   */
>  #include <linux/dma-map-ops.h>
>  
> +static struct page *cpu_addr_to_page(void *cpu_addr)
> +{
> +	if (is_vmalloc_addr(cpu_addr))
> +		return vmalloc_to_page(cpu_addr);
> +	else
> +		return virt_to_page(cpu_addr);
> +}

We have the same thing in xen_swiotlb_free_coherent. Can we find a way
to call cpu_addr_to_page() from xen_swiotlb_free_coherent? Maybe we can
make cpu_addr_to_page non-static? No problem if it is too much trouble.


>  /*
>   * Create scatter-list for the already allocated DMA buffer.
>   */
> @@ -12,7 +20,7 @@ int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
>  		 void *cpu_addr, dma_addr_t dma_addr, size_t size,
>  		 unsigned long attrs)
>  {
> -	struct page *page = virt_to_page(cpu_addr);
> +	struct page *page = cpu_addr_to_page(cpu_addr);
>  	int ret;
>  
>  	ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
> @@ -43,7 +51,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
>  		return -ENXIO;
>  
>  	return remap_pfn_range(vma, vma->vm_start,
> -			page_to_pfn(virt_to_page(cpu_addr)) + vma->vm_pgoff,
> +			page_to_pfn(cpu_addr_to_page(cpu_addr)) + vma->vm_pgoff,
>  			user_count << PAGE_SHIFT, vma->vm_page_prot);
>  #else
>  	return -ENXIO;
> -- 
> 2.25.1
>

Re: [PATCH v2] dma-mapping: use vmalloc_to_page for vmalloc addresses

Posted by Roman Skakun 2 years, 9 months ago

Hi, Stefano!

> We have the same thing in xen_swiotlb_free_coherent. Can we find a way
> to call cpu_addr_to_page() from xen_swiotlb_free_coherent?
> Maybe we can make cpu_addr_to_page non-static?

Yes, right, If we want to reuse this helper instead of the same code
block in xen_swiotlb_free_coherent() need to make cpu_addr_to_page() as
global and add a new declaration for this helper in include/linux/dma-map-ops.h.
What do you think?

Cheers!

ср, 14 июл. 2021 г. в 04:23, Stefano Stabellini <sstabellini@kernel.org>:
>
> On Tue, 22 Jun 2021, Roman Skakun wrote:
> > This commit is dedicated to fix incorrect conversion from
> > cpu_addr to page address in cases when we get virtual
> > address which allocated in the vmalloc range.
> > As the result, virt_to_page() cannot convert this address
> > properly and return incorrect page address.
> >
> > Need to detect such cases and obtains the page address using
> > vmalloc_to_page() instead.
> >
> > Signed-off-by: Roman Skakun <roman_skakun@epam.com>
> > Reviewed-by: Andrii Anisov <andrii_anisov@epam.com>
> > ---
> > Hey!
> > Thanks for suggestions, Christoph!
> > I updated the patch according to your advice.
> > But, I'm so surprised because nobody catches this problem
> > in the common code before. It looks a bit strange as for me.
> >
> >
> >  kernel/dma/ops_helpers.c | 12 ++++++++++--
> >  1 file changed, 10 insertions(+), 2 deletions(-)
> >
> > diff --git a/kernel/dma/ops_helpers.c b/kernel/dma/ops_helpers.c
> > index 910ae69cae77..782728d8a393 100644
> > --- a/kernel/dma/ops_helpers.c
> > +++ b/kernel/dma/ops_helpers.c
> > @@ -5,6 +5,14 @@
> >   */
> >  #include <linux/dma-map-ops.h>
> >
> > +static struct page *cpu_addr_to_page(void *cpu_addr)
> > +{
> > +     if (is_vmalloc_addr(cpu_addr))
> > +             return vmalloc_to_page(cpu_addr);
> > +     else
> > +             return virt_to_page(cpu_addr);
> > +}
>
> We have the same thing in xen_swiotlb_free_coherent. Can we find a way
> to call cpu_addr_to_page() from xen_swiotlb_free_coherent? Maybe we can
> make cpu_addr_to_page non-static? No problem if it is too much trouble.
>
>
> >  /*
> >   * Create scatter-list for the already allocated DMA buffer.
> >   */
> > @@ -12,7 +20,7 @@ int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
> >                void *cpu_addr, dma_addr_t dma_addr, size_t size,
> >                unsigned long attrs)
> >  {
> > -     struct page *page = virt_to_page(cpu_addr);
> > +     struct page *page = cpu_addr_to_page(cpu_addr);
> >       int ret;
> >
> >       ret = sg_alloc_table(sgt, 1, GFP_KERNEL);
> > @@ -43,7 +51,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
> >               return -ENXIO;
> >
> >       return remap_pfn_range(vma, vma->vm_start,
> > -                     page_to_pfn(virt_to_page(cpu_addr)) + vma->vm_pgoff,
> > +                     page_to_pfn(cpu_addr_to_page(cpu_addr)) + vma->vm_pgoff,
> >                       user_count << PAGE_SHIFT, vma->vm_page_prot);
> >  #else
> >       return -ENXIO;
> > --
> > 2.25.1
> >



-- 
Best Regards, Roman.