x86/mm/pat: Wrap pat_enabled into a function API
We use pat_enabled in x86-specific code to see if PAT is enabled
or not but we're granting full access to it even though readers
do not need to set it. If, for instance, we granted access to it
to modules later they then could override the variable
setting... no bueno.
This renames pat_enabled to a new static variable __pat_enabled.
Folks are redirected to use pat_enabled() now.
Code that sets this can only be internal to pat.c. Apart from
the early kernel parameter "nopat" to disable PAT, we also have
a few cases that disable it later and make use of a helper
pat_disable(). It is wrapped under an ifdef but since that code
cannot run unless PAT was enabled its not required to wrap it
with ifdefs, unwrap that. Likewise, since "nopat" doesn't really
change non-PAT systems just remove that ifdef as well.
Although we could add and use an early_param_off(), these
helpers don't use __read_mostly but we want to keep
__read_mostly for __pat_enabled as this is a hot path -- upon
boot, for instance, a simple guest may see ~4k accesses to
pat_enabled(). Since __read_mostly early boot params are not
that common we don't add a helper for them just yet.
Signed-off-by: Luis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Walls <awalls@md.metrocast.net>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dave Airlie <airlied@redhat.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Doug Ledford <dledford@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Juergen Gross <jgross@suse.com>
Cc: Kyle McMartin <kyle@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1430425520-22275-3-git-send-email-mcgrof@do-not-panic.com
Link: http://lkml.kernel.org/r/1432628901-18044-13-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h
index 91bc4ba..cdcff7f 100644
--- a/arch/x86/include/asm/pat.h
+++ b/arch/x86/include/asm/pat.h
@@ -4,12 +4,7 @@
#include <linux/types.h>
#include <asm/pgtable_types.h>
-#ifdef CONFIG_X86_PAT
-extern int pat_enabled;
-#else
-static const int pat_enabled;
-#endif
-
+bool pat_enabled(void);
extern void pat_init(void);
void pat_init_cache_modes(void);
diff --git a/arch/x86/kernel/cpu/mtrr/main.c b/arch/x86/kernel/cpu/mtrr/main.c
index 383efb2..e7ed0d8 100644
--- a/arch/x86/kernel/cpu/mtrr/main.c
+++ b/arch/x86/kernel/cpu/mtrr/main.c
@@ -558,7 +558,7 @@
{
int ret;
- if (pat_enabled || !mtrr_enabled())
+ if (pat_enabled() || !mtrr_enabled())
return 0; /* Success! (We don't need to do anything.) */
ret = mtrr_add(base, size, MTRR_TYPE_WRCOMB, true);
diff --git a/arch/x86/mm/iomap_32.c b/arch/x86/mm/iomap_32.c
index 9ca35fc..3a2ec87 100644
--- a/arch/x86/mm/iomap_32.c
+++ b/arch/x86/mm/iomap_32.c
@@ -82,7 +82,7 @@
* MTRR is UC or WC. UC_MINUS gets the real intention, of the
* user, which is "WC if the MTRR is WC, UC if you can't do that."
*/
- if (!pat_enabled && pgprot_val(prot) ==
+ if (!pat_enabled() && pgprot_val(prot) ==
(__PAGE_KERNEL | cachemode2protval(_PAGE_CACHE_MODE_WC)))
prot = __pgprot(__PAGE_KERNEL |
cachemode2protval(_PAGE_CACHE_MODE_UC_MINUS));
diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index a493bb8..82d63ed 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -234,7 +234,7 @@
{
/*
* Ideally, this should be:
- * pat_enabled ? _PAGE_CACHE_MODE_UC : _PAGE_CACHE_MODE_UC_MINUS;
+ * pat_enabled() ? _PAGE_CACHE_MODE_UC : _PAGE_CACHE_MODE_UC_MINUS;
*
* Till we fix all X drivers to use ioremap_wc(), we will use
* UC MINUS. Drivers that are certain they need or can already
@@ -292,7 +292,7 @@
*/
void __iomem *ioremap_wc(resource_size_t phys_addr, unsigned long size)
{
- if (pat_enabled)
+ if (pat_enabled())
return __ioremap_caller(phys_addr, size, _PAGE_CACHE_MODE_WC,
__builtin_return_address(0));
else
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 397838e..70d221f 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -1571,7 +1571,7 @@
{
int ret;
- if (!pat_enabled)
+ if (!pat_enabled())
return set_memory_uc(addr, numpages);
ret = reserve_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE,
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 8c50b9b..484dce7 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -36,12 +36,11 @@
#undef pr_fmt
#define pr_fmt(fmt) "" fmt
-#ifdef CONFIG_X86_PAT
-int __read_mostly pat_enabled = 1;
+static int __read_mostly __pat_enabled = IS_ENABLED(CONFIG_X86_PAT);
static inline void pat_disable(const char *reason)
{
- pat_enabled = 0;
+ __pat_enabled = 0;
pr_info("x86/PAT: %s\n", reason);
}
@@ -51,13 +50,11 @@
return 0;
}
early_param("nopat", nopat);
-#else
-static inline void pat_disable(const char *reason)
-{
- (void)reason;
-}
-#endif
+bool pat_enabled(void)
+{
+ return !!__pat_enabled;
+}
int pat_debug_enable;
@@ -201,7 +198,7 @@
u64 pat;
bool boot_cpu = !boot_pat_state;
- if (!pat_enabled)
+ if (!pat_enabled())
return;
if (!cpu_has_pat) {
@@ -402,7 +399,7 @@
BUG_ON(start >= end); /* end is exclusive */
- if (!pat_enabled) {
+ if (!pat_enabled()) {
/* This is identical to page table setting without PAT */
if (new_type) {
if (req_type == _PAGE_CACHE_MODE_WC)
@@ -477,7 +474,7 @@
int is_range_ram;
struct memtype *entry;
- if (!pat_enabled)
+ if (!pat_enabled())
return 0;
/* Low ISA region is always mapped WB. No need to track */
@@ -625,7 +622,7 @@
u64 to = from + size;
u64 cursor = from;
- if (!pat_enabled)
+ if (!pat_enabled())
return 1;
while (cursor < to) {
@@ -661,7 +658,7 @@
* caching for the high addresses through the KEN pin, but
* we maintain the tradition of paranoia in this code.
*/
- if (!pat_enabled &&
+ if (!pat_enabled() &&
!(boot_cpu_has(X86_FEATURE_MTRR) ||
boot_cpu_has(X86_FEATURE_K6_MTRR) ||
boot_cpu_has(X86_FEATURE_CYRIX_ARR) ||
@@ -730,7 +727,7 @@
* the type requested matches the type of first page in the range.
*/
if (is_ram) {
- if (!pat_enabled)
+ if (!pat_enabled())
return 0;
pcm = lookup_memtype(paddr);
@@ -844,7 +841,7 @@
return ret;
}
- if (!pat_enabled)
+ if (!pat_enabled())
return 0;
/*
@@ -872,7 +869,7 @@
{
enum page_cache_mode pcm;
- if (!pat_enabled)
+ if (!pat_enabled())
return 0;
/* Set prot based on lookup */
@@ -913,7 +910,7 @@
pgprot_t pgprot_writecombine(pgprot_t prot)
{
- if (pat_enabled)
+ if (pat_enabled())
return __pgprot(pgprot_val(prot) |
cachemode2protval(_PAGE_CACHE_MODE_WC));
else
@@ -996,7 +993,7 @@
static int __init pat_memtype_list_init(void)
{
- if (pat_enabled) {
+ if (pat_enabled()) {
debugfs_create_file("pat_memtype_list", S_IRUSR,
arch_debugfs_dir, NULL, &memtype_fops);
}
diff --git a/arch/x86/pci/i386.c b/arch/x86/pci/i386.c
index 349c0d3..0a9f2ca 100644
--- a/arch/x86/pci/i386.c
+++ b/arch/x86/pci/i386.c
@@ -429,12 +429,12 @@
* Caller can followup with UC MINUS request and add a WC mtrr if there
* is a free mtrr slot.
*/
- if (!pat_enabled && write_combine)
+ if (!pat_enabled() && write_combine)
return -EINVAL;
- if (pat_enabled && write_combine)
+ if (pat_enabled() && write_combine)
prot |= cachemode2protval(_PAGE_CACHE_MODE_WC);
- else if (pat_enabled || boot_cpu_data.x86 > 3)
+ else if (pat_enabled() || boot_cpu_data.x86 > 3)
/*
* ioremap() and ioremap_nocache() defaults to UC MINUS for now.
* To avoid attribute conflicts, request UC MINUS here