[PATCH 2/3] mm, x86: Remove region_is_ram() call from ioremap

Toshi Kani
2015-06-19T21:44:43Z

__ioremap_caller() calls region_is_ram() to look up the resource
to check if a target range is RAM, which was added as an additinal
check to improve the lookup performance over page_is_ram() (commit
906e36c5c717 "x86: use optimized ioresource lookup in ioremap
function").

__ioremap_caller() then calls walk_system_ram_range(), which had
replaced page_is_ram() to improve the lookup performance (commit
c81c8a1eeede "x86, ioremap: Speed up check for RAM pages").

Since both functions walk through the resource table, there is
no need to call the two functions. Furthermore, region_is_ram()
has bugs and always returns with -1. This makes
walk_system_ram_range() as the only check being used.

Hence, remove the call to region_is_ram() from __ioremap_caller().

Note, removing the call to region_is_ram() is also necessary
to fix the bugs in region_is_ram(). walk_system_ram_range()
requires RAM ranges aligned by the page size in the resource
table. e820_reserve_setup_data() updates the e820 table by
allocating a separate entry to each data region in setup_data,
which is not page-aligned. Therefore, walk_system_ram_range()
is unable to detect the RAM ranges in setup_data. This
restriction has allowed multiple uses of ioremap() to map
setup_data. Using fixed region_is_ram() will cause these callers
to start failing. After all ioremap to setup_data are converted,
__ioremap_caller() may call region_is_ram() instead.

Signed-off-by: Toshi Kani <toshi.kani@hp.com>
---
arch/x86/mm/ioremap.c | 24 ++++++------------------
1 file changed, 6 insertions(+), 18 deletions(-)

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 56f8af7..928867e 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -89,7 +89,6 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
pgprot_t prot;
int retval;
void __iomem *ret_addr;
- int ram_region;

/* Don't allow wraparound or zero size */
last_addr = phys_addr + size - 1;
@@ -112,26 +111,15 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr,
/*
* Don't allow anybody to remap normal RAM that we're using..
*/
- /* First check if whole region can be identified as RAM or not */
- ram_region = region_is_ram(phys_addr, size);
- if (ram_region > 0) {
- WARN_ONCE(1, "ioremap on RAM at 0x%lx - 0x%lx\n",
- (unsigned long int)phys_addr,
- (unsigned long int)last_addr);
- return NULL;
- }
-
- /* If could not be identified(-1), check page by page */
- if (ram_region < 0) {
- pfn = phys_addr >> PAGE_SHIFT;
- last_pfn = last_addr >> PAGE_SHIFT;
- if (walk_system_ram_range(pfn, last_pfn - pfn + 1, NULL,
+ pfn = phys_addr >> PAGE_SHIFT;
+ last_pfn = last_addr >> PAGE_SHIFT;
+ if (walk_system_ram_range(pfn, last_pfn - pfn + 1, NULL,
__ioremap_check_ram) == 1) {
- WARN_ONCE(1, "ioremap on RAM at 0x%llx - 0x%llx\n",
+ WARN_ONCE(1, "ioremap on RAM at 0x%llx - 0x%llx\n",
phys_addr, last_addr);
- return NULL;
- }
+ return NULL;
}
+
/*
* Mappings have to be page-aligned
*/