Patchwork [v2,04/10] DMA, CMA: support alignment constraint on cma region

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Submitter Joonsoo Kim
Date June 12, 2014, 3:21 a.m.
Message ID <1402543307-29800-5-git-send-email-iamjoonsoo.kim@lge.com>
Download mbox | patch
Permalink /patch/358962/
State New
Headers show

Comments

Joonsoo Kim - June 12, 2014, 3:21 a.m.
ppc kvm's cma area management needs alignment constraint on
cma region. So support it to prepare generalization of cma area
management functionality.

Additionally, add some comments which tell us why alignment
constraint is needed on cma region.

Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Aneesh Kumar K.V - June 12, 2014, 4:50 a.m.
Joonsoo Kim <iamjoonsoo.kim@lge.com> writes:

> ppc kvm's cma area management needs alignment constraint on
> cma region. So support it to prepare generalization of cma area
> management functionality.
>
> Additionally, add some comments which tell us why alignment
> constraint is needed on cma region.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

>
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index 8a44c82..bc4c171 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -32,6 +32,7 @@
>  #include <linux/swap.h>
>  #include <linux/mm_types.h>
>  #include <linux/dma-contiguous.h>
> +#include <linux/log2.h>
>
>  struct cma {
>  	unsigned long	base_pfn;
> @@ -219,6 +220,7 @@ core_initcall(cma_init_reserved_areas);
>   * @size: Size of the reserved area (in bytes),
>   * @base: Base address of the reserved area optional, use 0 for any
>   * @limit: End address of the reserved memory (optional, 0 for any).
> + * @alignment: Alignment for the contiguous memory area, should be power of 2
>   * @res_cma: Pointer to store the created cma region.
>   * @fixed: hint about where to place the reserved area
>   *
> @@ -233,15 +235,15 @@ core_initcall(cma_init_reserved_areas);
>   */
>  static int __init __dma_contiguous_reserve_area(phys_addr_t size,
>  				phys_addr_t base, phys_addr_t limit,
> +				phys_addr_t alignment,
>  				struct cma **res_cma, bool fixed)
>  {
>  	struct cma *cma = &cma_areas[cma_area_count];
> -	phys_addr_t alignment;
>  	int ret = 0;
>
> -	pr_debug("%s(size %lx, base %08lx, limit %08lx)\n", __func__,
> -		 (unsigned long)size, (unsigned long)base,
> -		 (unsigned long)limit);
> +	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
> +		__func__, (unsigned long)size, (unsigned long)base,
> +		(unsigned long)limit, (unsigned long)alignment);
>
>  	/* Sanity checks */
>  	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
> @@ -253,8 +255,17 @@ static int __init __dma_contiguous_reserve_area(phys_addr_t size,
>  	if (!size)
>  		return -EINVAL;
>
> -	/* Sanitise input arguments */
> -	alignment = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
> +	if (alignment && !is_power_of_2(alignment))
> +		return -EINVAL;
> +
> +	/*
> +	 * Sanitise input arguments.
> +	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
> +	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
> +	 * and CMA property will be broken.
> +	 */
> +	alignment = max(alignment,
> +		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
>  	base = ALIGN(base, alignment);
>  	size = ALIGN(size, alignment);
>  	limit &= ~(alignment - 1);
> @@ -302,7 +313,8 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
>  {
>  	int ret;
>
> -	ret = __dma_contiguous_reserve_area(size, base, limit, res_cma, fixed);
> +	ret = __dma_contiguous_reserve_area(size, base, limit, 0,
> +						res_cma, fixed);
>  	if (ret)
>  		return ret;
>
> -- 
> 1.7.9.5

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Minchan Kim - June 12, 2014, 5:52 a.m.
On Thu, Jun 12, 2014 at 12:21:41PM +0900, Joonsoo Kim wrote:
> ppc kvm's cma area management needs alignment constraint on
> cma region. So support it to prepare generalization of cma area
> management functionality.
> 
> Additionally, add some comments which tell us why alignment
> constraint is needed on cma region.
> 
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> 
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index 8a44c82..bc4c171 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -32,6 +32,7 @@
>  #include <linux/swap.h>
>  #include <linux/mm_types.h>
>  #include <linux/dma-contiguous.h>
> +#include <linux/log2.h>
>  
>  struct cma {
>  	unsigned long	base_pfn;
> @@ -219,6 +220,7 @@ core_initcall(cma_init_reserved_areas);
>   * @size: Size of the reserved area (in bytes),
>   * @base: Base address of the reserved area optional, use 0 for any
>   * @limit: End address of the reserved memory (optional, 0 for any).
> + * @alignment: Alignment for the contiguous memory area, should be power of 2
>   * @res_cma: Pointer to store the created cma region.
>   * @fixed: hint about where to place the reserved area
>   *

Pz, move the all description to new API function rather than internal one.

> @@ -233,15 +235,15 @@ core_initcall(cma_init_reserved_areas);
>   */
>  static int __init __dma_contiguous_reserve_area(phys_addr_t size,
>  				phys_addr_t base, phys_addr_t limit,
> +				phys_addr_t alignment,
>  				struct cma **res_cma, bool fixed)
>  {
>  	struct cma *cma = &cma_areas[cma_area_count];
> -	phys_addr_t alignment;
>  	int ret = 0;
>  
> -	pr_debug("%s(size %lx, base %08lx, limit %08lx)\n", __func__,
> -		 (unsigned long)size, (unsigned long)base,
> -		 (unsigned long)limit);
> +	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",

Why is it called by "align_order"?

> +		__func__, (unsigned long)size, (unsigned long)base,
> +		(unsigned long)limit, (unsigned long)alignment);
>  
>  	/* Sanity checks */
>  	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
> @@ -253,8 +255,17 @@ static int __init __dma_contiguous_reserve_area(phys_addr_t size,
>  	if (!size)
>  		return -EINVAL;
>  
> -	/* Sanitise input arguments */
> -	alignment = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
> +	if (alignment && !is_power_of_2(alignment))
> +		return -EINVAL;
> +
> +	/*
> +	 * Sanitise input arguments.
> +	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
> +	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism

I'm not a native but try for clear documenation.

         Pages both ends in CMA area could be merged into adjacent unmovable
         migratetype page by page allocator's buddy algorithm. In the case,
         you couldn't get a contiguous memory, which is not what we want.

> +	 * and CMA property will be broken.
> +	 */
> +	alignment = max(alignment,
> +		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
>  	base = ALIGN(base, alignment);
>  	size = ALIGN(size, alignment);
>  	limit &= ~(alignment - 1);
> @@ -302,7 +313,8 @@ int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
>  {
>  	int ret;
>  
> -	ret = __dma_contiguous_reserve_area(size, base, limit, res_cma, fixed);
> +	ret = __dma_contiguous_reserve_area(size, base, limit, 0,
> +						res_cma, fixed);
>  	if (ret)
>  		return ret;
>  
> -- 
> 1.7.9.5
Joonsoo Kim - June 12, 2014, 6:07 a.m.
On Thu, Jun 12, 2014 at 02:52:20PM +0900, Minchan Kim wrote:
> On Thu, Jun 12, 2014 at 12:21:41PM +0900, Joonsoo Kim wrote:
> > ppc kvm's cma area management needs alignment constraint on
> > cma region. So support it to prepare generalization of cma area
> > management functionality.
> > 
> > Additionally, add some comments which tell us why alignment
> > constraint is needed on cma region.
> > 
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> > 
> > diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> > index 8a44c82..bc4c171 100644
> > --- a/drivers/base/dma-contiguous.c
> > +++ b/drivers/base/dma-contiguous.c
> > @@ -32,6 +32,7 @@
> >  #include <linux/swap.h>
> >  #include <linux/mm_types.h>
> >  #include <linux/dma-contiguous.h>
> > +#include <linux/log2.h>
> >  
> >  struct cma {
> >  	unsigned long	base_pfn;
> > @@ -219,6 +220,7 @@ core_initcall(cma_init_reserved_areas);
> >   * @size: Size of the reserved area (in bytes),
> >   * @base: Base address of the reserved area optional, use 0 for any
> >   * @limit: End address of the reserved memory (optional, 0 for any).
> > + * @alignment: Alignment for the contiguous memory area, should be power of 2
> >   * @res_cma: Pointer to store the created cma region.
> >   * @fixed: hint about where to place the reserved area
> >   *
> 
> Pz, move the all description to new API function rather than internal one.

Reason I leave all description as is is that I will remove it in
following patch. I think that moving these makes patch bigger and hard
to review.

But, if it is necessary, I will do it. :)

> 
> > @@ -233,15 +235,15 @@ core_initcall(cma_init_reserved_areas);
> >   */
> >  static int __init __dma_contiguous_reserve_area(phys_addr_t size,
> >  				phys_addr_t base, phys_addr_t limit,
> > +				phys_addr_t alignment,
> >  				struct cma **res_cma, bool fixed)
> >  {
> >  	struct cma *cma = &cma_areas[cma_area_count];
> > -	phys_addr_t alignment;
> >  	int ret = 0;
> >  
> > -	pr_debug("%s(size %lx, base %08lx, limit %08lx)\n", __func__,
> > -		 (unsigned long)size, (unsigned long)base,
> > -		 (unsigned long)limit);
> > +	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
> 
> Why is it called by "align_order"?

Oops... mistake.
I will fix it.

Thanks.

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Michal Nazarewicz - June 12, 2014, 10:02 a.m.
On Thu, Jun 12 2014, Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:
> ppc kvm's cma area management needs alignment constraint on

I've noticed it earlier and cannot seem to get to terms with this.  It
should IMO be PPC, KVM and CMA since those are acronyms.  But if you
have strong feelings, it's not a big issue.

> cma region. So support it to prepare generalization of cma area
> management functionality.
>
> Additionally, add some comments which tell us why alignment
> constraint is needed on cma region.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Acked-by: Michal Nazarewicz <mina86@mina86.com>

> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index 8a44c82..bc4c171 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -219,6 +220,7 @@ core_initcall(cma_init_reserved_areas);
>   * @size: Size of the reserved area (in bytes),
>   * @base: Base address of the reserved area optional, use 0 for any
>   * @limit: End address of the reserved memory (optional, 0 for any).
> + * @alignment: Alignment for the contiguous memory area, should be
>  	power of 2

“must be power of 2 or zero”.

>   * @res_cma: Pointer to store the created cma region.
>   * @fixed: hint about where to place the reserved area
>   *
> @@ -233,15 +235,15 @@ core_initcall(cma_init_reserved_areas);
>   */
>  static int __init __dma_contiguous_reserve_area(phys_addr_t size,
>  				phys_addr_t base, phys_addr_t limit,
> +				phys_addr_t alignment,
>  				struct cma **res_cma, bool fixed)
>  {
>  	struct cma *cma = &cma_areas[cma_area_count];
> -	phys_addr_t alignment;
>  	int ret = 0;
>  
> -	pr_debug("%s(size %lx, base %08lx, limit %08lx)\n", __func__,
> -		 (unsigned long)size, (unsigned long)base,
> -		 (unsigned long)limit);
> +	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
> +		__func__, (unsigned long)size, (unsigned long)base,
> +		(unsigned long)limit, (unsigned long)alignment);

Nit: Align with the rest of the arguments, i.e.:

+	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
+		 __func__, (unsigned long)size, (unsigned long)base,
+		 (unsigned long)limit, (unsigned long)alignment);

>  
>  	/* Sanity checks */
>  	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
Joonsoo Kim - June 16, 2014, 5:19 a.m.
On Thu, Jun 12, 2014 at 12:02:38PM +0200, Michal Nazarewicz wrote:
> On Thu, Jun 12 2014, Joonsoo Kim <iamjoonsoo.kim@lge.com> wrote:
> > ppc kvm's cma area management needs alignment constraint on
> 
> I've noticed it earlier and cannot seem to get to terms with this.  It
> should IMO be PPC, KVM and CMA since those are acronyms.  But if you
> have strong feelings, it's not a big issue.

Yes, I will fix it.

> 
> > cma region. So support it to prepare generalization of cma area
> > management functionality.
> >
> > Additionally, add some comments which tell us why alignment
> > constraint is needed on cma region.
> >
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> 
> Acked-by: Michal Nazarewicz <mina86@mina86.com>
> 
> > diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> > index 8a44c82..bc4c171 100644
> > --- a/drivers/base/dma-contiguous.c
> > +++ b/drivers/base/dma-contiguous.c
> > @@ -219,6 +220,7 @@ core_initcall(cma_init_reserved_areas);
> >   * @size: Size of the reserved area (in bytes),
> >   * @base: Base address of the reserved area optional, use 0 for any
> >   * @limit: End address of the reserved memory (optional, 0 for any).
> > + * @alignment: Alignment for the contiguous memory area, should be
> >  	power of 2
> 
> “must be power of 2 or zero”.

Okay.

> >   * @res_cma: Pointer to store the created cma region.
> >   * @fixed: hint about where to place the reserved area
> >   *
> > @@ -233,15 +235,15 @@ core_initcall(cma_init_reserved_areas);
> >   */
> >  static int __init __dma_contiguous_reserve_area(phys_addr_t size,
> >  				phys_addr_t base, phys_addr_t limit,
> > +				phys_addr_t alignment,
> >  				struct cma **res_cma, bool fixed)
> >  {
> >  	struct cma *cma = &cma_areas[cma_area_count];
> > -	phys_addr_t alignment;
> >  	int ret = 0;
> >  
> > -	pr_debug("%s(size %lx, base %08lx, limit %08lx)\n", __func__,
> > -		 (unsigned long)size, (unsigned long)base,
> > -		 (unsigned long)limit);
> > +	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
> > +		__func__, (unsigned long)size, (unsigned long)base,
> > +		(unsigned long)limit, (unsigned long)alignment);
> 
> Nit: Align with the rest of the arguments, i.e.:
> 
> +	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
> +		 __func__, (unsigned long)size, (unsigned long)base,
> +		 (unsigned long)limit, (unsigned long)alignment);

What's the difference between mine and yours?

Thanks.
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Patch

diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
index 8a44c82..bc4c171 100644
--- a/drivers/base/dma-contiguous.c
+++ b/drivers/base/dma-contiguous.c
@@ -32,6 +32,7 @@ 
 #include <linux/swap.h>
 #include <linux/mm_types.h>
 #include <linux/dma-contiguous.h>
+#include <linux/log2.h>
 
 struct cma {
 	unsigned long	base_pfn;
@@ -219,6 +220,7 @@  core_initcall(cma_init_reserved_areas);
  * @size: Size of the reserved area (in bytes),
  * @base: Base address of the reserved area optional, use 0 for any
  * @limit: End address of the reserved memory (optional, 0 for any).
+ * @alignment: Alignment for the contiguous memory area, should be power of 2
  * @res_cma: Pointer to store the created cma region.
  * @fixed: hint about where to place the reserved area
  *
@@ -233,15 +235,15 @@  core_initcall(cma_init_reserved_areas);
  */
 static int __init __dma_contiguous_reserve_area(phys_addr_t size,
 				phys_addr_t base, phys_addr_t limit,
+				phys_addr_t alignment,
 				struct cma **res_cma, bool fixed)
 {
 	struct cma *cma = &cma_areas[cma_area_count];
-	phys_addr_t alignment;
 	int ret = 0;
 
-	pr_debug("%s(size %lx, base %08lx, limit %08lx)\n", __func__,
-		 (unsigned long)size, (unsigned long)base,
-		 (unsigned long)limit);
+	pr_debug("%s(size %lx, base %08lx, limit %08lx align_order %08lx)\n",
+		__func__, (unsigned long)size, (unsigned long)base,
+		(unsigned long)limit, (unsigned long)alignment);
 
 	/* Sanity checks */
 	if (cma_area_count == ARRAY_SIZE(cma_areas)) {
@@ -253,8 +255,17 @@  static int __init __dma_contiguous_reserve_area(phys_addr_t size,
 	if (!size)
 		return -EINVAL;
 
-	/* Sanitise input arguments */
-	alignment = PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order);
+	if (alignment && !is_power_of_2(alignment))
+		return -EINVAL;
+
+	/*
+	 * Sanitise input arguments.
+	 * CMA area should be at least MAX_ORDER - 1 aligned. Otherwise,
+	 * CMA area could be merged into other MIGRATE_TYPE by buddy mechanism
+	 * and CMA property will be broken.
+	 */
+	alignment = max(alignment,
+		(phys_addr_t)PAGE_SIZE << max(MAX_ORDER - 1, pageblock_order));
 	base = ALIGN(base, alignment);
 	size = ALIGN(size, alignment);
 	limit &= ~(alignment - 1);
@@ -302,7 +313,8 @@  int __init dma_contiguous_reserve_area(phys_addr_t size, phys_addr_t base,
 {
 	int ret;
 
-	ret = __dma_contiguous_reserve_area(size, base, limit, res_cma, fixed);
+	ret = __dma_contiguous_reserve_area(size, base, limit, 0,
+						res_cma, fixed);
 	if (ret)
 		return ret;