Commit 124fe20d authored by Dan Williams's avatar Dan Williams
Browse files

mm: enhance region_is_ram() to region_intersects() 



region_is_ram() is used to prevent the establishment of aliased mappings
to physical "System RAM" with incompatible cache settings.  However, it
uses "-1" to indicate both "unknown" memory ranges (ranges not described
by platform firmware) and "mixed" ranges (where the parameters describe
a range that partially overlaps "System RAM").

Fix this up by explicitly tracking the "unknown" vs "mixed" resource
cases and returning REGION_INTERSECTS, REGION_MIXED, or REGION_DISJOINT.
This re-write also adds support for detecting when the requested region
completely eclipses all of a resource.  Note, the implementation treats
overlaps between "unknown" and the requested memory type as
REGION_INTERSECTS.

Finally, other memory types can be passed in by name, for now the only
usage "System RAM".

Suggested-by: default avatarLuis R. Rodriguez <mcgrof@suse.com>
Reviewed-by: default avatarToshi Kani <toshi.kani@hp.com>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent f6ef5a2a

include/linux/mm.h

+8 −1
Original line number Diff line number Diff line
@@ -369,7 +369,14 @@ static inline int put_page_unless_one(struct page *page) 
}



extern int page_is_ram(unsigned long pfn);

extern int region_is_ram(resource_size_t phys_addr, unsigned long size);



enum {

	REGION_INTERSECTS,

	REGION_DISJOINT,

	REGION_MIXED,

};



int region_intersects(resource_size_t offset, size_t size, const char *type);



/* Support for virtually mapped pages */

struct page *vmalloc_to_page(const void *addr);

kernel/resource.c

+36 −25
Original line number Diff line number Diff line
@@ -492,40 +492,51 @@ int __weak page_is_ram(unsigned long pfn) 
}

EXPORT_SYMBOL_GPL(page_is_ram);



/*

 * Search for a resouce entry that fully contains the specified region.

 * If found, return 1 if it is RAM, 0 if not.

 * If not found, or region is not fully contained, return -1

/**

 * region_intersects() - determine intersection of region with known resources

 * @start: region start address

 * @size: size of region

 * @name: name of resource (in iomem_resource)

 *

 * Check if the specified region partially overlaps or fully eclipses a

 * resource identified by @name.  Return REGION_DISJOINT if the region

 * does not overlap @name, return REGION_MIXED if the region overlaps

 * @type and another resource, and return REGION_INTERSECTS if the

 * region overlaps @type and no other defined resource. Note, that

 * REGION_INTERSECTS is also returned in the case when the specified

 * region overlaps RAM and undefined memory holes.

 *

 * Used by the ioremap functions to ensure the user is not remapping RAM and is

 * a vast speed up over walking through the resource table page by page.

 * region_intersect() is used by memory remapping functions to ensure

 * the user is not remapping RAM and is a vast speed up over walking

 * through the resource table page by page.

 */

int region_is_ram(resource_size_t start, unsigned long size)

int region_intersects(resource_size_t start, size_t size, const char *name)

{

	struct resource *p;

	resource_size_t end = start + size - 1;

	unsigned long flags = IORESOURCE_MEM | IORESOURCE_BUSY;

	const char *name = "System RAM";

	int ret = -1;

	resource_size_t end = start + size - 1;

	int type = 0; int other = 0;

	struct resource *p;



	read_lock(&resource_lock);

	for (p = iomem_resource.child; p ; p = p->sibling) {

		if (p->end < start)

			continue;

		bool is_type = strcmp(p->name, name) == 0 && p->flags == flags;



		if (p->start <= start && end <= p->end) {

			/* resource fully contains region */

			if ((p->flags != flags) || strcmp(p->name, name))

				ret = 0;

			else

				ret = 1;

			break;

		}

		if (end < p->start)

			break;	/* not found */

		if (start >= p->start && start <= p->end)

			is_type ? type++ : other++;

		if (end >= p->start && end <= p->end)

			is_type ? type++ : other++;

		if (p->start >= start && p->end <= end)

			is_type ? type++ : other++;

	}

	read_unlock(&resource_lock);

	return ret;



	if (other == 0)

		return type ? REGION_INTERSECTS : REGION_DISJOINT;



	if (type)

		return REGION_MIXED;



	return REGION_DISJOINT;

}



void __weak arch_remove_reservations(struct resource *avail)

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