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Subject[patch] x86, pat: fix warn_on_once() while mapping 0-1MB range with /dev/mem
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Date
From: Suresh Siddha <suresh.b.siddha@intel.com>
Subject: x86, pat: fix warn_on_once() while mapping 0-1MB range
with /dev/mem

Jeff Mahoney reported:
> With Suse's hwinfo tool, on -tip:
> WARNING: at arch/x86/mm/pat.c:637 reserve_pfn_range+0x5b/0x26d()

reserve_pfn_range() is not tracking the memory range below 1MB
as non-RAM and as such is inconsistent with similar checks in
reserve_memtype() and free_memtype()

Rename the pagerange_is_ram() to pat_pagerange_is_ram() and add the
"track legacy 1MB region as non RAM" condition.

And also, fix reserve_pfn_range() to return -EINVAL, when the pfn
range is RAM. This is to be consistent with this API design.

Reported-and-tested-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
---
Index: tip/arch/x86/mm/pat.c
===================================================================
--- tip/arch/x86/mm/pat.c.orig
+++ tip/arch/x86/mm/pat.c
@@ -220,6 +220,33 @@ chk_conflict(struct memtype *new, struct
static struct memtype *cached_entry;
static u64 cached_start;

+static int pat_pagerange_is_ram(unsigned long start, unsigned long end)
+{
+ int ram_page = 0, not_rampage = 0;
+ unsigned long page_nr;
+
+ for (page_nr = (start >> PAGE_SHIFT); page_nr < (end >> PAGE_SHIFT);
+ ++page_nr) {
+ /*
+ * For legacy reasons, physical address range in the legacy ISA
+ * region is tracked as non-RAM. This will allow users of
+ * /dev/mem to map portions of legacy ISA region, even when
+ * some of those portions are listed(or not even listed) with
+ * different e820 types(RAM/reserved/..)
+ */
+ if (page_nr >= (ISA_END_ADDRESS >> PAGE_SHIFT) &&
+ page_is_ram(page_nr))
+ ram_page = 1;
+ else
+ not_rampage = 1;
+
+ if (ram_page == not_rampage)
+ return -1;
+ }
+
+ return ram_page;
+}
+
/*
* For RAM pages, mark the pages as non WB memory type using
* PageNonWB (PG_arch_1). We allow only one set_memory_uc() or
@@ -345,20 +372,12 @@ int reserve_memtype(u64 start, u64 end,
if (new_type)
*new_type = actual_type;

- /*
- * For legacy reasons, some parts of the physical address range in the
- * legacy 1MB region is treated as non-RAM (even when listed as RAM in
- * the e820 tables). So we will track the memory attributes of this
- * legacy 1MB region using the linear memtype_list always.
- */
- if (end >= ISA_END_ADDRESS) {
- is_range_ram = pagerange_is_ram(start, end);
- if (is_range_ram == 1)
- return reserve_ram_pages_type(start, end, req_type,
- new_type);
- else if (is_range_ram < 0)
- return -EINVAL;
- }
+ is_range_ram = pat_pagerange_is_ram(start, end);
+ if (is_range_ram == 1)
+ return reserve_ram_pages_type(start, end, req_type,
+ new_type);
+ else if (is_range_ram < 0)
+ return -EINVAL;

new = kmalloc(sizeof(struct memtype), GFP_KERNEL);
if (!new)
@@ -455,19 +474,11 @@ int free_memtype(u64 start, u64 end)
if (is_ISA_range(start, end - 1))
return 0;

- /*
- * For legacy reasons, some parts of the physical address range in the
- * legacy 1MB region is treated as non-RAM (even when listed as RAM in
- * the e820 tables). So we will track the memory attributes of this
- * legacy 1MB region using the linear memtype_list always.
- */
- if (end >= ISA_END_ADDRESS) {
- is_range_ram = pagerange_is_ram(start, end);
- if (is_range_ram == 1)
- return free_ram_pages_type(start, end);
- else if (is_range_ram < 0)
- return -EINVAL;
- }
+ is_range_ram = pat_pagerange_is_ram(start, end);
+ if (is_range_ram == 1)
+ return free_ram_pages_type(start, end);
+ else if (is_range_ram < 0)
+ return -EINVAL;

spin_lock(&memtype_lock);
list_for_each_entry(entry, &memtype_list, nd) {
@@ -635,17 +646,13 @@ static int reserve_pfn_range(u64 paddr,
unsigned long flags;
unsigned long want_flags = (pgprot_val(*vma_prot) & _PAGE_CACHE_MASK);

- is_ram = pagerange_is_ram(paddr, paddr + size);
+ is_ram = pat_pagerange_is_ram(paddr, paddr + size);

- if (is_ram != 0) {
- /*
- * For mapping RAM pages, drivers need to call
- * set_memory_[uc|wc|wb] directly, for reserve and free, before
- * setting up the PTE.
- */
- WARN_ON_ONCE(1);
- return 0;
- }
+ /*
+ * reserve_pfn_range() doesn't support RAM pages.
+ */
+ if (is_ram != 0)
+ return -EINVAL;

ret = reserve_memtype(paddr, paddr + size, want_flags, &flags);
if (ret)
@@ -702,7 +709,7 @@ static void free_pfn_range(u64 paddr, un
{
int is_ram;

- is_ram = pagerange_is_ram(paddr, paddr + size);
+ is_ram = pat_pagerange_is_ram(paddr, paddr + size);
if (is_ram == 0)
free_memtype(paddr, paddr + size);
}
Index: tip/arch/x86/mm/ioremap.c
===================================================================
--- tip/arch/x86/mm/ioremap.c.orig
+++ tip/arch/x86/mm/ioremap.c
@@ -134,25 +134,6 @@ int page_is_ram(unsigned long pagenr)
return 0;
}

-int pagerange_is_ram(unsigned long start, unsigned long end)
-{
- int ram_page = 0, not_rampage = 0;
- unsigned long page_nr;
-
- for (page_nr = (start >> PAGE_SHIFT); page_nr < (end >> PAGE_SHIFT);
- ++page_nr) {
- if (page_is_ram(page_nr))
- ram_page = 1;
- else
- not_rampage = 1;
-
- if (ram_page == not_rampage)
- return -1;
- }
-
- return ram_page;
-}
-
/*
* Fix up the linear direct mapping of the kernel to avoid cache
attribute
* conflicts.
Index: tip/arch/x86/include/asm/page.h
===================================================================
--- tip/arch/x86/include/asm/page.h.orig
+++ tip/arch/x86/include/asm/page.h
@@ -57,7 +57,6 @@ typedef struct { pgdval_t pgd; } pgd_t;
typedef struct { pgprotval_t pgprot; } pgprot_t;

extern int page_is_ram(unsigned long pagenr);
-extern int pagerange_is_ram(unsigned long start, unsigned long end);
extern int devmem_is_allowed(unsigned long pagenr);
extern void map_devmem(unsigned long pfn, unsigned long size,
pgprot_t vma_prot);



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