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Commit cb32edf6 authored by Luis R. Rodriguez's avatar Luis R. Rodriguez Committed by Ingo Molnar
Browse files

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: default avatarLuis R. Rodriguez <mcgrof@suse.com>
Signed-off-by: default avatarBorislav 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: default avatarIngo Molnar <mingo@kernel.org>
parent f9626104

arch/x86/include/asm/pat.h

+1 −6
Original line number Diff line number Diff line
@@ -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);

arch/x86/kernel/cpu/mtrr/main.c

+1 −1
Original line number Diff line number Diff line
@@ -558,7 +558,7 @@ int arch_phys_wc_add(unsigned long base, unsigned long size) 
{

	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);

arch/x86/mm/iomap_32.c

+1 −1
Original line number Diff line number Diff line
@@ -82,7 +82,7 @@ iomap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot) 
	 * 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));

arch/x86/mm/ioremap.c

+2 −2
Original line number Diff line number Diff line
@@ -234,7 +234,7 @@ void __iomem *ioremap_nocache(resource_size_t phys_addr, unsigned long size) 
{

	/*

	 * 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 @@ EXPORT_SYMBOL_GPL(ioremap_uc); 
 */

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

arch/x86/mm/pageattr.c

+1 −1
Original line number Diff line number Diff line
@@ -1571,7 +1571,7 @@ int set_memory_wc(unsigned long addr, int numpages) 
{

	int ret;



	if (!pat_enabled)

	if (!pat_enabled())

		return set_memory_uc(addr, numpages);



	ret = reserve_memtype(__pa(addr), __pa(addr) + numpages * PAGE_SIZE,