Re: [Bug 11388] New: 2.6.27-rc3 warns about MTRR range; only 3 of 16gb of memory is usable

Yinghai Lu
2008-08-22T06:17:16Z

On Thu, Aug 21, 2008 at 8:50 PM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Yinghai Lu <yhlu.kernel@gmail.com> wrote:
>
>> or please try attached workaround patch. hope it works.
>>
>> Ingo,
>> if it works, we need to push it for 2.6.27
>
> i've tidied up your patch (see the commit below) and have queued it up
> in x86/urgent. It seems fairly safe and i guess we can push it to
> v2.6.27 if Joshua reports test success. Joshua, could you give it a go
> please?
>
> Ingo
>
> -------------->
> From 38cc1c3df77c1bb739a4766788eb9fa49f16ffdf Mon Sep 17 00:00:00 2001
> From: Yinghai Lu <yhlu.kernel@gmail.com>
> Date: Thu, 21 Aug 2008 20:24:24 -0700
> Subject: [PATCH] x86: work around MTRR mask setting
>
> Joshua Hoblitt reported that only 3 GB of his 16 GB of RAM is
> usable. Booting with mtrr_show showed us the BIOS-initialized
> MTRR settings - which are all wrong.
>
> So the root cause is that the BIOS has not set the mask correctly:
>
>> [ 0.429971] MSR00000200: 00000000d0000000
>> [ 0.433305] MSR00000201: 0000000ff0000800
>> should be ==> [ 0.433305] MSR00000201: 0000003ff0000800
>>
>> [ 0.436638] MSR00000202: 00000000e0000000
>> [ 0.439971] MSR00000203: 0000000fe0000800
>> should be ==> [ 0.439971] MSR00000203: 0000003fe0000800
>>
>> [ 0.443304] MSR00000204: 0000000000000006
>> [ 0.446637] MSR00000205: 0000000c00000800
>> should be ==> [ 0.446637] MSR00000205: 0000003c00000800
>>
>> [ 0.449970] MSR00000206: 0000000400000006
>> [ 0.453303] MSR00000207: 0000000fe0000800
>> should be ==> [ 0.453303] MSR00000207: 0000003fe0000800
>>
>> [ 0.456636] MSR00000208: 0000000420000006
>> [ 0.459970] MSR00000209: 0000000ff0000800
>> should be ==> [ 0.459970] MSR00000209: 0000003ff0000800
>
> So detect this borkage and add the prefix 111.
>
> Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>
> Cc: <stable@kernel.org>
> Signed-off-by: Ingo Molnar <mingo@elte.hu>
> ---
> arch/x86/kernel/cpu/mtrr/generic.c | 15 +++++++++++++--
> 1 files changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
> index 509bd3d..43102e0 100644
> --- a/arch/x86/kernel/cpu/mtrr/generic.c
> +++ b/arch/x86/kernel/cpu/mtrr/generic.c
> @@ -379,6 +379,7 @@ static void generic_get_mtrr(unsigned int reg, unsigned long *base,
> unsigned long *size, mtrr_type *type)
> {
> unsigned int mask_lo, mask_hi, base_lo, base_hi;
> + unsigned int tmp, hi;
>
> rdmsr(MTRRphysMask_MSR(reg), mask_lo, mask_hi);
> if ((mask_lo & 0x800) == 0) {
> @@ -392,8 +393,18 @@ static void generic_get_mtrr(unsigned int reg, unsigned long *base,
> rdmsr(MTRRphysBase_MSR(reg), base_lo, base_hi);
>
> /* Work out the shifted address mask. */
> - mask_lo = size_or_mask | mask_hi << (32 - PAGE_SHIFT)
> - | mask_lo >> PAGE_SHIFT;
> + tmp = mask_hi << (32 - PAGE_SHIFT) | mask_lo >> PAGE_SHIFT;
> + mask_lo = size_or_mask | tmp;
> + /* Expand tmp with high bits to all 1s*/
> + hi = fls(tmp);
> + if (hi > 0) {
> + tmp |= ~((1<<(hi - 1)) - 1);
> +
> + if (tmp != mask_lo) {
> + WARN_ON("mtrr: your BIOS has set up an incorrect mask, fixing it up.\n");

can you change WARN_ON to WARN_ON_ONCE ?

YH