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authorLuis R. Rodriguez <mcgrof@suse.com>2015-05-26 10:28:15 +0200
committerIngo Molnar <mingo@kernel.org>2015-05-27 14:41:01 +0200
commitcb32edf65bf2197a2d2226e94c7602dc92e295bb (patch)
treee75ba97e6fce4d3467f9cfe8423249f3743d33b5 /arch/x86/include/asm/pat.h
parentf9626104a5b6815ec7d65789dfb900af5fa51e64 (diff)
downloadlinux-cb32edf65bf2197a2d2226e94c7602dc92e295bb.tar.bz2
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>
Diffstat (limited to 'arch/x86/include/asm/pat.h')
-rw-r--r--arch/x86/include/asm/pat.h7
1 files changed, 1 insertions, 6 deletions
diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h
index 91bc4ba95f91..cdcff7f7f694 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);