[PATCH v3 01/10] KVM: MMU: fix decoding cache type from MTRR

Xiao Guangrong
2015-05-13T06:50:12Z

There are some bugs in current get_mtrr_type();
1: bit 1 of mtrr_state->enabled is corresponding bit 11 of
IA32_MTRR_DEF_TYPE MSR which completely control MTRR's enablement
that means other bits are ignored if it is cleared

2: the fixed MTRR ranges are controlled by bit 0 of
mtrr_state->enabled (bit 10 of IA32_MTRR_DEF_TYPE)

3: if MTRR is disabled, UC is applied to all of physical memory rather
than mtrr_state->def_type

Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
---
arch/x86/kvm/mmu.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index b78e83f..d00cebd 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -2393,19 +2393,20 @@ EXPORT_SYMBOL_GPL(kvm_mmu_unprotect_page);
static int get_mtrr_type(struct mtrr_state_type *mtrr_state,
u64 start, u64 end)
{
- int i;
u64 base, mask;
u8 prev_match, curr_match;
- int num_var_ranges = KVM_NR_VAR_MTRR;
+ int i, num_var_ranges = KVM_NR_VAR_MTRR;

- if (!mtrr_state->enabled)
- return 0xFF;
+ /* MTRR is completely disabled, use UC for all of physical memory. */
+ if (!(mtrr_state->enabled & 0x2))
+ return MTRR_TYPE_UNCACHABLE;

/* 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 (mtrr_state->have_fixed && (mtrr_state->enabled & 0x1) &&
+ (start < 0x100000)) {
int idx;

if (start < 0x80000) {
@@ -2428,9 +2429,6 @@ static int get_mtrr_type(struct mtrr_state_type *mtrr_state,
* 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;
--
2.1.0