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: Luis R. Rodriguez <mcgrof@suse.com> Reviewed-by: Toshi Kani <toshi.kani@hp.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
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2 changed files with 43 additions and 25 deletions
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@ -369,7 +369,14 @@ static inline int put_page_unless_one(struct page *page)
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}
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}
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extern int page_is_ram(unsigned long pfn);
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extern int page_is_ram(unsigned long pfn);
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extern int region_is_ram(resource_size_t phys_addr, unsigned long size);
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enum {
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REGION_INTERSECTS,
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REGION_DISJOINT,
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REGION_MIXED,
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};
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int region_intersects(resource_size_t offset, size_t size, const char *type);
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/* Support for virtually mapped pages */
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/* Support for virtually mapped pages */
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struct page *vmalloc_to_page(const void *addr);
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struct page *vmalloc_to_page(const void *addr);
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@ -492,40 +492,51 @@ int __weak page_is_ram(unsigned long pfn)
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}
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}
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EXPORT_SYMBOL_GPL(page_is_ram);
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EXPORT_SYMBOL_GPL(page_is_ram);
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/*
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/**
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* Search for a resouce entry that fully contains the specified region.
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* region_intersects() - determine intersection of region with known resources
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* If found, return 1 if it is RAM, 0 if not.
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* @start: region start address
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* If not found, or region is not fully contained, return -1
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* @size: size of region
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* @name: name of resource (in iomem_resource)
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*
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*
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* Used by the ioremap functions to ensure the user is not remapping RAM and is
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* Check if the specified region partially overlaps or fully eclipses a
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* a vast speed up over walking through the resource table page by page.
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* resource identified by @name. Return REGION_DISJOINT if the region
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* does not overlap @name, return REGION_MIXED if the region overlaps
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* @type and another resource, and return REGION_INTERSECTS if the
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* region overlaps @type and no other defined resource. Note, that
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* REGION_INTERSECTS is also returned in the case when the specified
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* region overlaps RAM and undefined memory holes.
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*
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* region_intersect() is used by memory remapping functions to ensure
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* the user is not remapping RAM and is a vast speed up over walking
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* through the resource table page by page.
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*/
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*/
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int region_is_ram(resource_size_t start, unsigned long size)
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int region_intersects(resource_size_t start, size_t size, const char *name)
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{
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{
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struct resource *p;
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resource_size_t end = start + size - 1;
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unsigned long flags = IORESOURCE_MEM | IORESOURCE_BUSY;
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unsigned long flags = IORESOURCE_MEM | IORESOURCE_BUSY;
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const char *name = "System RAM";
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resource_size_t end = start + size - 1;
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int ret = -1;
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int type = 0; int other = 0;
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struct resource *p;
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read_lock(&resource_lock);
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read_lock(&resource_lock);
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for (p = iomem_resource.child; p ; p = p->sibling) {
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for (p = iomem_resource.child; p ; p = p->sibling) {
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if (p->end < start)
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bool is_type = strcmp(p->name, name) == 0 && p->flags == flags;
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continue;
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if (p->start <= start && end <= p->end) {
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if (start >= p->start && start <= p->end)
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/* resource fully contains region */
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is_type ? type++ : other++;
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if ((p->flags != flags) || strcmp(p->name, name))
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if (end >= p->start && end <= p->end)
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ret = 0;
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is_type ? type++ : other++;
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else
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if (p->start >= start && p->end <= end)
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ret = 1;
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is_type ? type++ : other++;
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break;
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}
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if (end < p->start)
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break; /* not found */
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}
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}
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read_unlock(&resource_lock);
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read_unlock(&resource_lock);
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return ret;
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if (other == 0)
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return type ? REGION_INTERSECTS : REGION_DISJOINT;
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if (type)
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return REGION_MIXED;
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return REGION_DISJOINT;
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}
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}
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void __weak arch_remove_reservations(struct resource *avail)
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void __weak arch_remove_reservations(struct resource *avail)
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