[PATCH v4 2/7] mtrr, x86: Fix MTRR lookup to handle inclusive entry
From: Toshi Kani <hidden>
Date: 2015-03-24 22:27:53
Also in:
lkml
Subsystem:
the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
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, __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 (!start_state && end_state). With this fix, __mtrr_type_lookup() handles the inclusive case properly. Signed-off-by: Toshi Kani <redacted> --- arch/x86/kernel/cpu/mtrr/generic.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 7d74f7b..a82e370 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;
@@ -166,15 +166,16 @@ 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 or inclusive:1 + * (start:mtrr_start) (mtrr_start: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
@@ -195,7 +196,7 @@ static u8 __mtrr_type_lookup(u64 start, u64 end, u64 *partial_end, int *repeat) *repeat = 1; } - if ((start & mask) != (base & mask)) + if (!start_state) continue; curr_match = mtrr_state.var_ranges[i].base_lo & 0xff; --
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