Re: [PATCH v4 1/4] of: reserved_mem: Restruture how the reserved memory regions are processed

[Oreoluwa Babatunde]

On 3/11/2024 10:13 AM, Rob Herring wrote:
> On Fri, Mar 08, 2024 at 11:12:01AM -0800, Oreoluwa Babatunde wrote:
>> The current implementation processes the reserved memory regions in two
>> stages which are done with two separate functions within the
>> early_init_fdt_scan_reserved_mem() function.
>>
>> Within the two stages of processing, the reserved memory regions are
>> broken up into two groups which are processed differently:
>> i) Statically-placed reserved memory regions
>> i.e. regions defined with a static start address and size using the
>>      "reg" property in the DT.
>> ii) Dynamically-placed reserved memory regions.
>> i.e. regions defined by specifying a range of addresses where they can
>>      be placed in memory using the "alloc_ranges" and "size" properties
>>      in the DT.
>>
>> Stage 1: fdt_scan_reserved_mem()
>> This stage of the reserved memory processing is used to scan through the
>> reserved memory nodes defined in the devicetree and do the following on
>> each of the nodes:
>>
>> 1) If the node represents a statically-placed reserved memory region,
>>    i.e. it is defined using the "reg" property:
>>    - Call memblock_reserve() or memblock_mark_nomap() as needed.
>>    - Add the information for the reserved region to the reserved_mem array.
>>      eg: fdt_reserved_mem_save_node(node, name, base, size);
>>
>> 2) If the node represents a dynamically-placed reserved memory region,
>>    i.e. it is defined using "alloc-ranges" and "size" properties:
>>    - Add the information for the region to the reserved_mem array with
>>      the starting address and size set to 0.
>>      eg: fdt_reserved_mem_save_node(node, name, 0, 0);
>>
>> Stage 2: fdt_init_reserved_mem()
>> This stage of the reserved memory processing is used to iterate through
>> the reserved_mem array which was populated in stage 1 and do the
>> following on each of the entries:
>>
>> 1) If the entry represents a statically-placed reserved memory region:
>>    - Call the region specific init function.
>> 2) If the entry represents a dynamically-placed reserved memory region:
>>    - Call __reserved_mem_alloc_size() which is used to allocate memory
>>      for the region using memblock_phys_alloc_range(), and call
>>      memblock_mark_nomap() on the allocated region if the region is
>>      specified as a no-map region.
>>    - Call the region specific init function.
>>
>> On architectures such as arm64, the dynamic allocation of the
>> reserved_mem array needs to be done after the page tables have been
>> setup because memblock allocated memory is not writable until then. This
>> means that the reserved_mem array will not be available to store any
>> reserved memory information until after the page tables have been setup.
>>
>> It is possible to call memblock_reserve() and memblock_mark_nomap() on
>> the statically-placed reserved memory regions and not need to save them
>> to the reserved_mem array until later. This is because all the
>> information we need is present in the devicetree.
>> Dynamically-placed reserved memory regions on the other hand get assigned
>> a start address only at runtime, and since memblock_reserve() and
>> memblock_mark_nomap() need to be called before the memory mappings are
>> created, the allocation needs to happen before the page tables are setup.
>>
>> To make it easier to handle dynamically-placed reserved memory regions
>> before the page tables are setup, this patch makes changes to the steps
>> above to process the reserved memory regions in the following ways:
>>
>> Step 1: fdt_scan_reserved_mem()
>> This stage of the reserved memory processing is used to scan through the
>> reserved memory nodes defined in the devicetree and do the following on
>> each of the nodes:
>>
>> 1) If the node represents a statically-placed reserved memory region,
>>    i.e. it is defined using the "reg" property:
>>    - Call memblock_reserve() or memblock_mark_nomap() as needed.
>>
>> 2) If the node represents a dynamically-placed reserved memory region,
>>    i.e. it is defined using "alloc-ranges" and "size" properties:
>>    - Call __reserved_mem_alloc_size() which will:
>>      i) Allocate memory for the reserved memory region.
>>      ii) Call memblock_mark_nomap() as needed.
>>      Note: There is no need to explicitly call memblock_reserve() here
>>      because it is already called by memblock when the memory for the
>>      region is being allocated.
>>      iii) Save the information for the region in the reserved_mem array.
>>
>> Step 2: fdt_init_reserved_mem()
>> This stage of the reserved memory processing is used to:
>>
>> 1) Add the information for the statically-placed reserved memory into
>>    the reserved_mem array.
>>
>> 2) Iterate through all the entries in the array and call the region
>>    specific init function for each of them.
>>
>> Signed-off-by: Oreoluwa Babatunde <quic_obabatun@xxxxxxxxxxx>
>> ---
>>  drivers/of/fdt.c                | 84 ++++++++++++++++++++++++++++++---
>>  drivers/of/of_private.h         |  2 +-
>>  drivers/of/of_reserved_mem.c    | 54 +++++++++------------
>>  include/linux/of_fdt.h          |  1 +
>>  include/linux/of_reserved_mem.h |  9 ++++
>>  5 files changed, 111 insertions(+), 39 deletions(-)
>>
>> diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
>> index bf502ba8da95..fe6c75c5a8c0 100644
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -504,7 +504,6 @@ static int __init __reserved_mem_reserve_reg(unsigned long node,
>>  	phys_addr_t base, size;
>>  	int len;
>>  	const __be32 *prop;
>> -	int first = 1;
>>  	bool nomap;
>>  
>>  	prop = of_get_flat_dt_prop(node, "reg", &len);
>> @@ -532,10 +531,6 @@ static int __init __reserved_mem_reserve_reg(unsigned long node,
>>  			       uname, &base, (unsigned long)(size / SZ_1M));
>>  
>>  		len -= t_len;
>> -		if (first) {
>> -			fdt_reserved_mem_save_node(node, uname, base, size);
>> -			first = 0;
>> -		}
>>  	}
>>  	return 0;
>>  }
>> @@ -563,12 +558,70 @@ static int __init __reserved_mem_check_root(unsigned long node)
>>  	return 0;
>>  }
>>  
>> +/**
>> + * fdt_scan_reserved_mem_reg_nodes() - Store info for the "reg" defined
>> + * reserved memory regions.
>> + *
>> + * This function is used to scan through the DT and store the
>> + * information for the reserved memory regions that are defined using
>> + * the "reg" property. The region node number, name, base address, and
>> + * size are all stored in the reserved_mem array by calling the
>> + * fdt_reserved_mem_save_node() function.
>> + */
>> +void __init fdt_scan_reserved_mem_reg_nodes(void)
>> +
>> +{
>> +	int t_len = (dt_root_addr_cells + dt_root_size_cells) * sizeof(__be32);
>> +	const void *fdt = initial_boot_params;
>> +	phys_addr_t base, size;
>> +	const __be32 *prop;
>> +	int node, child;
>> +	int len;
>> +
>> +	node = fdt_path_offset(fdt, "/reserved-memory");
>> +	if (node < 0) {
>> +		pr_err("Reserved memory: Did not find reserved-memory node\n");
> No reserved regions is perfectly valid.
ack
>> +		return;
>> +	}
>> +
>> +	if (__reserved_mem_check_root(node)) {
>> +		pr_err("Reserved memory: unsupported node format, ignoring\n");
>> +		return;
>> +	}
>> +
>> +	fdt_for_each_subnode(child, fdt, node) {
>> +		const char *uname;
>> +
>> +		prop = of_get_flat_dt_prop(child, "reg", &len);
>> +		if (!prop)
>> +			continue;
>> +
>> +		if (!of_fdt_device_is_available(fdt, child))
>> +			continue;
>> +
>> +		uname = fdt_get_name(fdt, child, NULL);
>> +		if (len && len % t_len != 0) {
>> +			pr_err("Reserved memory: invalid reg property in '%s', skipping node.\n",
>> +			       uname);
>> +			continue;
>> +		}
>> +
>> +		base = dt_mem_next_cell(dt_root_addr_cells, &prop);
>> +		size = dt_mem_next_cell(dt_root_size_cells, &prop);
>> +
>> +		if (size)
>> +			fdt_reserved_mem_save_node(child, uname, base, size);
>> +	}
>> +}
>> +
>>  /*
>>   * fdt_scan_reserved_mem() - scan a single FDT node for reserved memory
>>   */
>>  static int __init fdt_scan_reserved_mem(void)
>>  {
>>  	int node, child;
>> +	int dynamic_nodes_cnt = 0;
>> +	int dynamic_nodes[MAX_RESERVED_REGIONS];
>>  	const void *fdt = initial_boot_params;
>>  
>>  	node = fdt_path_offset(fdt, "/reserved-memory");
>> @@ -590,8 +643,25 @@ static int __init fdt_scan_reserved_mem(void)
>>  		uname = fdt_get_name(fdt, child, NULL);
>>  
>>  		err = __reserved_mem_reserve_reg(child, uname);
>> -		if (err == -ENOENT && of_get_flat_dt_prop(child, "size", NULL))
>> -			fdt_reserved_mem_save_node(child, uname, 0, 0);
>> +
>> +		/*
>> +		 * Delay allocation of the dynamically-placed regions
>> +		 * until after all other statically-placed regions have
>> +		 * been reserved or marked as nomap
>> +		 */
>> +		if (err == -ENOENT && of_get_flat_dt_prop(child, "size", NULL)) {
>> +			dynamic_nodes[dynamic_nodes_cnt] = child;
>> +			dynamic_nodes_cnt++;
> Can't you just call __reserved_mem_alloc_size() here instead of looping 
> twice?
The reason for looping twice here is in the comment right above the
if-statement; "Delay allocation of the dynamically-placed regions until
after all other statically-placed regions have been reserved or marked
as nomap".

If we call "__reserved_mem_alloc_size()" at this point then there is a
possibility of allocating memory from one of the statically-placed
reserved memory regions since not all of them have been marked as
reserved or nomap yet.
>> +		}
>> +	}
>> +
>> +	for (int i = 0; i < dynamic_nodes_cnt; i++) {
>> +		const char *uname;
>> +
>> +		child = dynamic_nodes[i];
>> +		uname = fdt_get_name(fdt, child, NULL);
>> +
>> +		__reserved_mem_alloc_size(child, uname);
>>  	}
>>  	return 0;
>>  }
>> diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
>> index f38397c7b582..542e37a37a24 100644
>> --- a/drivers/of/of_private.h
>> +++ b/drivers/of/of_private.h
>> @@ -36,6 +36,7 @@ struct alias_prop {
>>  #endif
>>  
>>  #define OF_ROOT_NODE_SIZE_CELLS_DEFAULT 1
>> +#define MAX_RESERVED_REGIONS    64
>>  
>>  extern struct mutex of_mutex;
>>  extern raw_spinlock_t devtree_lock;
>> @@ -175,7 +176,6 @@ static inline struct device_node *__of_get_dma_parent(const struct device_node *
>>  }
>>  #endif
>>  
>> -void fdt_init_reserved_mem(void);
> I don't see why this is moved.
True, there is no need for this anymore.
Will revert it in the next revision.
>> [...]
>>
>> @@ -328,30 +325,25 @@ void __init fdt_init_reserved_mem(void)
>>  		if (prop)
>>  			rmem->phandle = of_read_number(prop, len/4);
>>  
>> -		if (rmem->size == 0)
>> -			err = __reserved_mem_alloc_size(node, rmem->name,
>> -						 &rmem->base, &rmem->size);
>> -		if (err == 0) {
>> -			err = __reserved_mem_init_node(rmem);
>> -			if (err != 0 && err != -ENOENT) {
>> -				pr_info("node %s compatible matching fail\n",
>> -					rmem->name);
>> -				if (nomap)
>> -					memblock_clear_nomap(rmem->base, rmem->size);
>> -				else
>> -					memblock_phys_free(rmem->base,
>> -							   rmem->size);
>> -			} else {
>> -				phys_addr_t end = rmem->base + rmem->size - 1;
>> -				bool reusable =
>> -					(of_get_flat_dt_prop(node, "reusable", NULL)) != NULL;
>> -
>> -				pr_info("%pa..%pa (%lu KiB) %s %s %s\n",
>> -					&rmem->base, &end, (unsigned long)(rmem->size / SZ_1K),
>> -					nomap ? "nomap" : "map",
>> -					reusable ? "reusable" : "non-reusable",
>> -					rmem->name ? rmem->name : "unknown");
>> -			}
>> +		err = __reserved_mem_init_node(rmem);
>> +		if (err != 0 && err != -ENOENT) {
>> +			pr_info("node %s compatible matching fail\n",
>> +				rmem->name);
> Can be 1 line now.
ack.
>> +			if (nomap)
>> +				memblock_clear_nomap(rmem->base, rmem->size);
>> +			else
>> +				memblock_phys_free(rmem->base,
>> +						   rmem->size);
> Can be 1 line now.
ack.
>> +		} else {
>> +			phys_addr_t end = rmem->base + rmem->size - 1;
>> +			bool reusable =
>> +				(of_get_flat_dt_prop(node, "reusable", NULL)) != NULL;
>> +
>> +			pr_info("%pa..%pa (%lu KiB) %s %s %s\n",
>> +				&rmem->base, &end, (unsigned long)(rmem->size / SZ_1K),
>> +				nomap ? "nomap" : "map",
>> +				reusable ? "reusable" : "non-reusable",
>> +				rmem->name ? rmem->name : "unknown");
>>  		}
>>  	}
>>  }
>> diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
>> index d69ad5bb1eb1..7b2a5d93d719 100644
>> --- a/include/linux/of_fdt.h
>> +++ b/include/linux/of_fdt.h
>> @@ -73,6 +73,7 @@ extern int early_init_dt_scan_root(void);
>>  extern bool early_init_dt_scan(void *params);
>>  extern bool early_init_dt_verify(void *params);
>>  extern void early_init_dt_scan_nodes(void);
>> +extern void fdt_scan_reserved_mem_reg_nodes(void);
> This is internal to drivers/of/, so it goes in of_private.h
ack.
>>  
>>  extern const char *of_flat_dt_get_machine_name(void);
>>  extern const void *of_flat_dt_match_machine(const void *default_match,
>> diff --git a/include/linux/of_reserved_mem.h b/include/linux/of_reserved_mem.h
>> index 4de2a24cadc9..2a3178920bae 100644
>> --- a/include/linux/of_reserved_mem.h
>> +++ b/include/linux/of_reserved_mem.h
>> @@ -32,12 +32,14 @@ typedef int (*reservedmem_of_init_fn)(struct reserved_mem *rmem);
>>  #define RESERVEDMEM_OF_DECLARE(name, compat, init)			\
>>  	_OF_DECLARE(reservedmem, name, compat, init, reservedmem_of_init_fn)
>>  
>> +void fdt_init_reserved_mem(void);
>>  int of_reserved_mem_device_init_by_idx(struct device *dev,
>>  				       struct device_node *np, int idx);
>>  int of_reserved_mem_device_init_by_name(struct device *dev,
>>  					struct device_node *np,
>>  					const char *name);
>>  void of_reserved_mem_device_release(struct device *dev);
>> +int __reserved_mem_alloc_size(unsigned long node, const char *uname);
> This is internal to drivers/of/, so it goes in of_private.h
ack.
>
> But really, I think fdt_scan_reserved_mem() should move to 
> of_reserved_mem.c first. Then everything you add to fdt.c goes there 
> too.
ack.



Regards,

Oreoluwa