From: Toshi Kani <toshi.k...@hp.com> When an MTRR entry is inclusive to a requested range, i.e. the start and end of the request are not within the MTRR entry range but the range contains the MTRR entry entirely:
range_start ... [mtrr_start ... mtrr_end] ... range_end __mtrr_type_lookup() ignores such a case because both start_state and end_state are set to zero. This bug can cause the following issues: 1) reserve_memtype() tracks an effective memory type in case a request type is WB (ex. /dev/mem blindly uses WB). Missing to track with its effective type causes a subsequent request to map the same range with the effective type to fail. 2) pud_set_huge() and pmd_set_huge() check if a requested range has any overlap with MTRRs. Missing to detect an overlap may cause a performance penalty or undefined behavior. This patch fixes the bug by adding a new flag, 'inclusive', to detect the inclusive case. This case is then handled in the same way as end_state:1 since the first region is the same. With this fix, __mtrr_type_lookup() handles the inclusive case properly. Signed-off-by: Toshi Kani <toshi.k...@hp.com> Cc: dave.han...@intel.com Cc: elli...@hp.com Cc: pebo...@tiscali.nl Cc: Luis R. Rodriguez <mcg...@suse.com> Cc: Andrew Morton <a...@linux-foundation.org> Cc: H. Peter Anvin <h...@zytor.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Ingo Molnar <mi...@kernel.org> Cc: linux-mm <linux...@kvack.org> Cc: x86-ml <x...@kernel.org> Cc: lkml <linux-kernel@vger.kernel.org> Link: http://lkml.kernel.org/r/1431714237-880-3-git-send-email-toshi.k...@hp.com Signed-off-by: Borislav Petkov <b...@suse.de> --- arch/x86/kernel/cpu/mtrr/generic.c | 28 ++++++++++++++++++---------- 1 file changed, 18 insertions(+), 10 deletions(-) diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c index 5b239679cfc9..e202d26f64a2 100644 --- a/arch/x86/kernel/cpu/mtrr/generic.c +++ b/arch/x86/kernel/cpu/mtrr/generic.c @@ -154,7 +154,7 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat) prev_match = 0xFF; for (i = 0; i < num_var_ranges; ++i) { - unsigned short start_state, end_state; + unsigned short start_state, end_state, inclusive; if (!(mtrr_state.var_ranges[i].mask_lo & (1 << 11))) continue; @@ -166,19 +166,27 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat) start_state = ((start & mask) == (base & mask)); end_state = ((end & mask) == (base & mask)); + inclusive = ((start < base) && (end > base)); - if (start_state != end_state) { + if ((start_state != end_state) || inclusive) { /* * We have start:end spanning across an MTRR. - * We split the region into - * either - * (start:mtrr_end) (mtrr_end:end) - * or - * (start:mtrr_start) (mtrr_start:end) + * We split the region into either + * + * - start_state:1 + * (start:mtrr_end)(mtrr_end:end) + * - end_state:1 + * (start:mtrr_start)(mtrr_start:end) + * - inclusive:1 + * (start:mtrr_start)(mtrr_start:mtrr_end)(mtrr_end:end) + * * depending on kind of overlap. - * Return the type for first region and a pointer to - * the start of second region so that caller will - * lookup again on the second region. + * + * Return the type of the first region and a pointer + * to the start of next region so that caller will be + * advised to lookup again after having adjusted start + * and end. + * * Note: This way we handle multiple overlaps as well. */ if (start_state) -- 1.9.0.258.g00eda23 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
