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

Yinghai Lu
2008-08-22T03:24:36Z

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On Thu, Aug 21, 2008 at 7:26 PM, Yinghai Lu <yhlu.kernel@gmail.com> wrote:
> On Thu, Aug 21, 2008 at 7:15 PM, Joshua Hoblitt <josh@hoblitt.com> wrote:
>> On Thu, Aug 21, 2008 at 06:55:58PM -0700, Yinghai Lu wrote:
>> address sizes : 38 bits physical, 48 bits virtual
>
> good, the root cause is your bios not set mask correctly...
>
> it should set var mtrr like
>
> [ 0.429971] MSR00000200: 00000000d0000000
> [ 0.433305] MSR00000201: 0000000ff0000800
> ==> [ 0.433305] MSR00000201: 0000003ff0000800
>
> [ 0.436638] MSR00000202: 00000000e0000000
> [ 0.439971] MSR00000203: 0000000fe0000800
> ==> [ 0.439971] MSR00000203: 0000003fe0000800
>
> [ 0.443304] MSR00000204: 0000000000000006
> [ 0.446637] MSR00000205: 0000000c00000800
> ==> [ 0.446637] MSR00000205: 0000003c00000800
>
> [ 0.449970] MSR00000206: 0000000400000006
> [ 0.453303] MSR00000207: 0000000fe0000800
> ==>[ 0.453303] MSR00000207: 0000003fe0000800
>
> [ 0.456636] MSR00000208: 0000000420000006
> [ 0.459970] MSR00000209: 0000000ff0000800
> ==> [ 0.459970] MSR00000209: 0000003ff0000800
>
> you may talk to your BIOS vendor or system vendor to request one new
> updated BIOS.
>

or please try attached workaround patch. hope it works.

Ingo,
if it works, we need to push it for 2.6.27

YH

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[PATCH] x86: workaroun mtrr mask setting

Some BIOS doesn't set mtrr mask correctly, workaround it be prefix 111

Signed-off-by: Yinghai Lu <yhlu.kernel@gmail.com>

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 509bd3d..a17d5ba 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;
+ /* expend tmp with high bits to all 1s*/
+ hi = fls(tmp);
+ if (hi > 0) {
+ tmp |= ~((1<<(hi - 1)) - 1);
+
+ if (tmp != mask_lo) {
+ WARN_ON("You BIOS mask set is wrong, complain to vendor\n");
+ mask_lo = tmp;
+ }
+ }

/* This works correctly if size is a power of two, i.e. a
contiguous range. */