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Commit 9b3aca62 authored by Toshi Kani's avatar Toshi Kani Committed by Ingo Molnar
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x86/mm/mtrr: Fix MTRR state checks in mtrr_type_lookup() 



'mtrr_state.enabled' contains the FE (fixed MTRRs enabled)
and E (MTRRs enabled) flags in MSR_MTRRdefType.  Intel SDM,
section 11.11.2.1, defines these flags as follows:

 - All MTRRs are disabled when the E flag is clear.
   The FE flag has no affect when the E flag is clear.
 - The default type is enabled when the E flag is set.
 - MTRR variable ranges are enabled when the E flag is set.
 - MTRR fixed ranges are enabled when both E and FE flags
   are set.

MTRR state checks in __mtrr_type_lookup() do not match with SDM.

Hence, this patch makes the following changes:
 - The current code detects MTRRs disabled when both E and
   FE flags are clear in mtrr_state.enabled.  Fix to detect
   MTRRs disabled when the E flag is clear.
 - The current code does not check if the FE bit is set in
   mtrr_state.enabled when looking at the fixed entries.
   Fix to check the FE flag.
 - The current code returns the default type when the E flag
   is clear in mtrr_state.enabled. However, the default type
   is UC when the E flag is clear.  Remove the code as this
   case is handled as MTRR disabled with the 1st change.

In addition, this patch defines the E and FE flags in
mtrr_state.enabled as follows.
 - FE flag: MTRR_STATE_MTRR_FIXED_ENABLED
 - E  flag: MTRR_STATE_MTRR_ENABLED

print_mtrr_state() and x86_get_mtrr_mem_range() are also updated
accordingly.

Signed-off-by: default avatarToshi Kani <toshi.kani@hp.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Elliott@hp.com
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luis R. Rodriguez <mcgrof@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dave.hansen@intel.com
Cc: linux-mm <linux-mm@kvack.org>
Cc: pebolle@tiscali.nl
Link: http://lkml.kernel.org/r/1431714237-880-4-git-send-email-toshi.kani@hp.com
Link: http://lkml.kernel.org/r/1432628901-18044-4-git-send-email-bp@alien8.de


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 7f0431e3

arch/x86/include/asm/mtrr.h

+4 −0
Original line number Diff line number Diff line
@@ -127,4 +127,8 @@ struct mtrr_gentry32 { 
				 _IOW(MTRR_IOCTL_BASE,  9, struct mtrr_sentry32)

#endif /* CONFIG_COMPAT */



/* Bit fields for enabled in struct mtrr_state_type */

#define MTRR_STATE_MTRR_FIXED_ENABLED	0x01

#define MTRR_STATE_MTRR_ENABLED		0x02



#endif /* _ASM_X86_MTRR_H */

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

+2 −1
Original line number Diff line number Diff line
@@ -98,7 +98,8 @@ x86_get_mtrr_mem_range(struct range *range, int nr_range, 
			continue;

		base = range_state[i].base_pfn;

		if (base < (1<<(20-PAGE_SHIFT)) && mtrr_state.have_fixed &&

		    (mtrr_state.enabled & 1)) {

		    (mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED) &&

		    (mtrr_state.enabled & MTRR_STATE_MTRR_FIXED_ENABLED)) {

			/* Var MTRR contains UC entry below 1M? Skip it: */

			printk(BIOS_BUG_MSG, i);

			if (base + size <= (1<<(20-PAGE_SHIFT)))

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

+8 −7
Original line number Diff line number Diff line
@@ -119,14 +119,16 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat) 
	if (!mtrr_state_set)

		return 0xFF;



	if (!mtrr_state.enabled)

	if (!(mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED))

		return 0xFF;



	/* Make end inclusive end, instead of exclusive */

	end--;



	/* Look in fixed ranges. Just return the type as per start */

	if (mtrr_state.have_fixed && (start < 0x100000)) {

	if ((start < 0x100000) &&

	    (mtrr_state.have_fixed) &&

	    (mtrr_state.enabled & MTRR_STATE_MTRR_FIXED_ENABLED)) {

		int idx;



		if (start < 0x80000) {
@@ -149,9 +151,6 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat) 
	 * Look of multiple ranges matching this address and pick type

	 * as per MTRR precedence

	 */

	if (!(mtrr_state.enabled & 2))

		return mtrr_state.def_type;



	prev_match = 0xFF;

	for (i = 0; i < num_var_ranges; ++i) {

		unsigned short start_state, end_state, inclusive;
@@ -355,7 +354,9 @@ static void __init print_mtrr_state(void) 
		 mtrr_attrib_to_str(mtrr_state.def_type));

	if (mtrr_state.have_fixed) {

		pr_debug("MTRR fixed ranges %sabled:\n",

			 mtrr_state.enabled & 1 ? "en" : "dis");

			((mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED) &&

			 (mtrr_state.enabled & MTRR_STATE_MTRR_FIXED_ENABLED)) ?

			 "en" : "dis");

		print_fixed(0x00000, 0x10000, mtrr_state.fixed_ranges + 0);

		for (i = 0; i < 2; ++i)

			print_fixed(0x80000 + i * 0x20000, 0x04000,
@@ -368,7 +369,7 @@ static void __init print_mtrr_state(void) 
		print_fixed_last();

	}

	pr_debug("MTRR variable ranges %sabled:\n",

		 mtrr_state.enabled & 2 ? "en" : "dis");

		 mtrr_state.enabled & MTRR_STATE_MTRR_ENABLED ? "en" : "dis");

	high_width = (__ffs64(size_or_mask) - (32 - PAGE_SHIFT) + 3) / 4;



	for (i = 0; i < num_var_ranges; ++i) {