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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20080822035024.GB30284@elte.hu>
Date:	Fri, 22 Aug 2008 05:50:24 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Joshua Hoblitt <josh@...litt.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	bugme-daemon@...zilla.kernel.org, linux-kernel@...r.kernel.org,
	j_kernel@...litt.com
Subject: Re: [Bug 11388] New: 2.6.27-rc3 warns about MTRR range; only 3 of
	16gb of memory is usable


* Yinghai Lu <yhlu.kernel@...il.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@...il.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@...il.com>
Cc: <stable@...nel.org>
Signed-off-by: Ingo Molnar <mingo@...e.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");
+			mask_lo = tmp;
+		}
+	}
 
 	/* This works correctly if size is a power of two, i.e. a
 	   contiguous range. */
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/