Re: [PATCH v4 4/7] mtrr, x86: Fix MTRR state checks in mtrr_type_lookup()

Borislav Petkov
2015-05-06T11:47:15Z

On Tue, Mar 24, 2015 at 04:08:38PM -0600, Toshi Kani wrote:
> '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 into 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 also disabled when the E flag is clear. Fix to 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() is also updated accordingly.
>
> Signed-off-by: Toshi Kani <toshi.kani@hp.com>
> ---
> arch/x86/include/uapi/asm/mtrr.h | 4 ++++
> arch/x86/kernel/cpu/mtrr/generic.c | 15 ++++++++-------
> 2 files changed, 12 insertions(+), 7 deletions(-)

You missed a spot in the conversion in
arch/x86/kernel/cpu/mtrr/cleanup.c::x86_get_mtrr_mem_range():

There we have

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

which should be mtrr_state.enabled & MTRR_STATE_MTRR_FIXED_ENABLED.

> diff --git a/arch/x86/include/uapi/asm/mtrr.h b/arch/x86/include/uapi/asm/mtrr.h
> index d0acb65..66ba88d 100644
> --- a/arch/x86/include/uapi/asm/mtrr.h
> +++ b/arch/x86/include/uapi/asm/mtrr.h
> @@ -88,6 +88,10 @@ struct mtrr_state_type {
> mtrr_type def_type;
> };
>
> +/* Bit fields for enabled in struct mtrr_state_type */
> +#define MTRR_STATE_MTRR_FIXED_ENABLED 0x01
> +#define MTRR_STATE_MTRR_ENABLED 0x02
> +
> #define MTRRphysBase_MSR(reg) (0x200 + 2 * (reg))
> #define MTRRphysMask_MSR(reg) (0x200 + 2 * (reg) + 1)

Please add those to arch/x86/include/asm/mtrr.h instead. They have no
place in the uapi header.

--
Regards/Gruss,
Boris.

ECO tip #101: Trim your mails when you reply.
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