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

["Yinghai Lu" <yhlu.kernel@gmail.com>]

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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. */