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[PATCH 3/3] cma: move allocation from HIGHMEM to a helper function

Mike Rapoport posted 3 patches 3 months, 1 week ago
[PATCH 3/3] cma: move allocation from HIGHMEM to a helper function
Posted by Mike Rapoport 3 months, 1 week ago 
From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>

When CONFIG_HIGMEM is enabled, __cma_declare_contiguous_nid() first
tries to allocate the area from HIGHMEM and if that fails it falls back
to allocation from low memory.

Split allocation from HIGMEM into a helper function to further decouple
logic related to CONFIG_HIGHMEM.

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
---
 mm/cma.c | 52 +++++++++++++++++++++++++++++-----------------------
 1 file changed, 29 insertions(+), 23 deletions(-)

diff --git a/mm/cma.c b/mm/cma.c
index 1df8ff312d99..0a24c46f3296 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -376,6 +376,30 @@ static int __init cma_fixed_reserve(phys_addr_t base, phys_addr_t size)
 	return 0;
 }
 
+static phys_addr_t __init cma_alloc_highmem(phys_addr_t base, phys_addr_t size,
+			phys_addr_t align, phys_addr_t *limit, int nid)
+{
+	phys_addr_t addr = 0;
+
+	if (IS_ENABLED(CONFIG_HIGHMEM)) {
+		phys_addr_t highmem = __pa(high_memory - 1) + 1;
+
+		/*
+		 * All pages in the reserved area must come from the same zone.
+		 * If the requested region crosses the low/high memory boundary,
+		 * try allocating from high memory first and fall back to low
+		 * memory in case of failure.
+		 */
+		if (base < highmem && *limit > highmem) {
+			addr = memblock_alloc_range_nid(size, align, highmem,
+							*limit, nid, true);
+			*limit = highmem;
+		}
+	}
+
+	return addr;
+}
+
 static int __init __cma_declare_contiguous_nid(phys_addr_t *basep,
 			phys_addr_t size, phys_addr_t limit,
 			phys_addr_t alignment, unsigned int order_per_bit,
@@ -383,19 +407,9 @@ static int __init __cma_declare_contiguous_nid(phys_addr_t *basep,
 			int nid)
 {
 	phys_addr_t memblock_end = memblock_end_of_DRAM();
-	phys_addr_t highmem_start, base = *basep;
+	phys_addr_t base = *basep;
 	int ret;
 
-	/*
-	 * We can't use __pa(high_memory) directly, since high_memory
-	 * isn't a valid direct map VA, and DEBUG_VIRTUAL will (validly)
-	 * complain. Find the boundary by adding one to the last valid
-	 * address.
-	 */
-	if (IS_ENABLED(CONFIG_HIGHMEM))
-		highmem_start = __pa(high_memory - 1) + 1;
-	else
-		highmem_start = memblock_end_of_DRAM();
 	pr_debug("%s(size %pa, base %pa, limit %pa alignment %pa)\n",
 		__func__, &size, &base, &limit, &alignment);
 
@@ -472,18 +486,10 @@ static int __init __cma_declare_contiguous_nid(phys_addr_t *basep,
 		}
 #endif
 
-		/*
-		 * All pages in the reserved area must come from the same zone.
-		 * If the requested region crosses the low/high memory boundary,
-		 * try allocating from high memory first and fall back to low
-		 * memory in case of failure.
-		 */
-		if (!addr && base < highmem_start && limit > highmem_start) {
-			addr = memblock_alloc_range_nid(size, alignment,
-					highmem_start, limit, nid, true);
-			limit = highmem_start;
-		}
-
+		/* On systems with HIGHMEM try allocating from there first */
+		if (!addr)
+			addr = cma_alloc_highmem(base, size, alignment, &limit,
+						 nid);
 		if (!addr) {
 			addr = memblock_alloc_range_nid(size, alignment, base,
 					limit, nid, true);
-- 
2.47.2
Re: [PATCH 3/3] cma: move allocation from HIGHMEM to a helper function
Posted by Oscar Salvador 3 months ago 
On Wed, Jul 02, 2025 at 08:36:05PM +0300, Mike Rapoport wrote:
> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> 
> When CONFIG_HIGMEM is enabled, __cma_declare_contiguous_nid() first
> tries to allocate the area from HIGHMEM and if that fails it falls back
> to allocation from low memory.
> 
> Split allocation from HIGMEM into a helper function to further decouple
> logic related to CONFIG_HIGHMEM.
> 
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>  mm/cma.c | 52 +++++++++++++++++++++++++++++-----------------------
>  1 file changed, 29 insertions(+), 23 deletions(-)
> 
> diff --git a/mm/cma.c b/mm/cma.c
> index 1df8ff312d99..0a24c46f3296 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -376,6 +376,30 @@ static int __init cma_fixed_reserve(phys_addr_t base, phys_addr_t size)
>  	return 0;
>  }
>  
> +static phys_addr_t __init cma_alloc_highmem(phys_addr_t base, phys_addr_t size,
> +			phys_addr_t align, phys_addr_t *limit, int nid)
> +{
> +	phys_addr_t addr = 0;
> +
> +	if (IS_ENABLED(CONFIG_HIGHMEM)) {
> +		phys_addr_t highmem = __pa(high_memory - 1) + 1;
> +
> +		/*
> +		 * All pages in the reserved area must come from the same zone.
> +		 * If the requested region crosses the low/high memory boundary,
> +		 * try allocating from high memory first and fall back to low
> +		 * memory in case of failure.
> +		 */
> +		if (base < highmem && *limit > highmem) {
> +			addr = memblock_alloc_range_nid(size, align, highmem,
> +							*limit, nid, true);
> +			*limit = highmem;
> +		}
> +	}

Not a big deal, but maybe better to do it in one function? Maybe even move
the CONFIG_PHYS_ADDR_T_64BIT block in there as well? So memblock_alloc_range_nid()
calls would be contained in one place and the X86_64/HIGHMEM comments as
well.
Just a thought.

 diff --git a/mm/cma.c b/mm/cma.c
 index dd7643fc01db..532b56e6971a 100644
 --- a/mm/cma.c
 +++ b/mm/cma.c
 @@ -377,11 +377,12 @@ static int __init cma_fixed_reserve(phys_addr_t base, phys_addr_t size)
  	return 0;
  }
 
 -static phys_addr_t __init cma_alloc_highmem(phys_addr_t base, phys_addr_t size,
 -			phys_addr_t align, phys_addr_t *limit, int nid)
 +static phys_addr_t __init cma_alloc_mem(phys_addr_t base, phys_addr_t size,
 +			phys_addr_t align, phys_addr_t limit, int nid)
  {
  	phys_addr_t addr = 0;
 
 +	/* On systems with HIGHMEM try allocating from there first */
  	if (IS_ENABLED(CONFIG_HIGHMEM)) {
  		phys_addr_t highmem = __pa(high_memory - 1) + 1;
 
 @@ -393,11 +394,15 @@ static phys_addr_t __init cma_alloc_highmem(phys_addr_t base, phys_addr_t size,
  		 */
  		if (base < highmem && *limit > highmem) {
  			addr = memblock_alloc_range_nid(size, align, highmem,
 -							*limit, nid, true);
 +							limit, nid, true);
  			*limit = highmem;
  		}
  	}
 
 +	if (!addr)
 +		addr = memblock_alloc_range_nid(size, alignment, base,
 +						limit, nid, true);
 +
  	return addr;
  }
 
 @@ -487,16 +492,8 @@ static int __init __cma_declare_contiguous_nid(phys_addr_t *basep,
  		}
  #endif
 
 -		/* On systems with HIGHMEM try allocating from there first */
  		if (!addr)
 -			addr = cma_alloc_highmem(base, size, alignment, &limit,
 -						 nid);
 -		if (!addr) {
 -			addr = memblock_alloc_range_nid(size, alignment, base,
 -					limit, nid, true);
 -			if (!addr)
 -				return -ENOMEM;
 -		}
 +			addr = cma_alloc_mem(base, size, alignment, limit, nid);
 
  		/*
  		 * kmemleak scans/reads tracked objects for pointers to other



-- 
Oscar Salvador
SUSE Labs
Re: [PATCH 3/3] cma: move allocation from HIGHMEM to a helper function
Posted by Mike Rapoport 3 months ago 
On Thu, Jul 03, 2025 at 11:53:06AM +0200, Oscar Salvador wrote:
> On Wed, Jul 02, 2025 at 08:36:05PM +0300, Mike Rapoport wrote:
> > From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
> > 
> > When CONFIG_HIGMEM is enabled, __cma_declare_contiguous_nid() first
> > tries to allocate the area from HIGHMEM and if that fails it falls back
> > to allocation from low memory.
> > 
> > Split allocation from HIGMEM into a helper function to further decouple
> > logic related to CONFIG_HIGHMEM.
> > 
> > Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> > ---
> >  mm/cma.c | 52 +++++++++++++++++++++++++++++-----------------------
> >  1 file changed, 29 insertions(+), 23 deletions(-)
> > 
> > diff --git a/mm/cma.c b/mm/cma.c
> > index 1df8ff312d99..0a24c46f3296 100644
> > --- a/mm/cma.c
> > +++ b/mm/cma.c
> > @@ -376,6 +376,30 @@ static int __init cma_fixed_reserve(phys_addr_t base, phys_addr_t size)
> >  	return 0;
> >  }
> >  
> > +static phys_addr_t __init cma_alloc_highmem(phys_addr_t base, phys_addr_t size,
> > +			phys_addr_t align, phys_addr_t *limit, int nid)
> > +{
> > +	phys_addr_t addr = 0;
> > +
> > +	if (IS_ENABLED(CONFIG_HIGHMEM)) {
> > +		phys_addr_t highmem = __pa(high_memory - 1) + 1;
> > +
> > +		/*
> > +		 * All pages in the reserved area must come from the same zone.
> > +		 * If the requested region crosses the low/high memory boundary,
> > +		 * try allocating from high memory first and fall back to low
> > +		 * memory in case of failure.
> > +		 */
> > +		if (base < highmem && *limit > highmem) {
> > +			addr = memblock_alloc_range_nid(size, align, highmem,
> > +							*limit, nid, true);
> > +			*limit = highmem;
> > +		}
> > +	}
> 
> Not a big deal, but maybe better to do it in one function? Maybe even move
> the CONFIG_PHYS_ADDR_T_64BIT block in there as well? So memblock_alloc_range_nid()
> calls would be contained in one place and the X86_64/HIGHMEM comments as
> well.
> Just a thought.

Yeah, this will be neater, thanks!
Will send v2 shortly.

> -- 
> Oscar Salvador
> SUSE Labs

-- 
Sincerely yours,
Mike.
Re: [PATCH 3/3] cma: move allocation from HIGHMEM to a helper function
Posted by David Hildenbrand 3 months ago 
On 03.07.25 11:53, Oscar Salvador wrote:
> On Wed, Jul 02, 2025 at 08:36:05PM +0300, Mike Rapoport wrote:
>> From: "Mike Rapoport (Microsoft)" <rppt@kernel.org>
>>
>> When CONFIG_HIGMEM is enabled, __cma_declare_contiguous_nid() first
>> tries to allocate the area from HIGHMEM and if that fails it falls back
>> to allocation from low memory.
>>
>> Split allocation from HIGMEM into a helper function to further decouple
>> logic related to CONFIG_HIGHMEM.
>>
>> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
>> ---
>>   mm/cma.c | 52 +++++++++++++++++++++++++++++-----------------------
>>   1 file changed, 29 insertions(+), 23 deletions(-)
>>
>> diff --git a/mm/cma.c b/mm/cma.c
>> index 1df8ff312d99..0a24c46f3296 100644
>> --- a/mm/cma.c
>> +++ b/mm/cma.c
>> @@ -376,6 +376,30 @@ static int __init cma_fixed_reserve(phys_addr_t base, phys_addr_t size)
>>   	return 0;
>>   }
>>   
>> +static phys_addr_t __init cma_alloc_highmem(phys_addr_t base, phys_addr_t size,
>> +			phys_addr_t align, phys_addr_t *limit, int nid)
>> +{
>> +	phys_addr_t addr = 0;
>> +
>> +	if (IS_ENABLED(CONFIG_HIGHMEM)) {
>> +		phys_addr_t highmem = __pa(high_memory - 1) + 1;
>> +
>> +		/*
>> +		 * All pages in the reserved area must come from the same zone.
>> +		 * If the requested region crosses the low/high memory boundary,
>> +		 * try allocating from high memory first and fall back to low
>> +		 * memory in case of failure.
>> +		 */
>> +		if (base < highmem && *limit > highmem) {
>> +			addr = memblock_alloc_range_nid(size, align, highmem,
>> +							*limit, nid, true);
>> +			*limit = highmem;
>> +		}
>> +	}
> 
> Not a big deal, but maybe better to do it in one function? 

Yes, same thought here.

-- 
Cheers,

David / dhildenb

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