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

Wanpeng Li
2015-05-13T08:27:17Z

On Wed, May 13, 2015 at 02:42:19PM +0800, Xiao Guangrong wrote:
>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>

Reviewed-by: Wanpeng Li <wanpeng.li@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
>
>--
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