-stable review patch. If anyone has any objections, please let us know.
---------------------
From: Andreas Herrmann <[email protected]>
upstream commit: 3ff42da5048649503e343a32be37b14a6a4e8aaf
Impact: bug fix + BIOS workaround
BIOS is expected to clear the SYSCFG[MtrrFixDramModEn] on AMD CPUs
after fixed MTRRs are configured.
Some BIOSes do not clear SYSCFG[MtrrFixDramModEn] on BP (and on APs).
This can lead to obfuscation in Linux when this bit is not cleared on
BP but cleared on APs. A consequence of this is that the saved
fixed-MTRR state (from BP) differs from the fixed-MTRRs of APs --
because RdDram/WrDram bits are read as zero when
SYSCFG[MtrrFixDramModEn] is cleared -- and Linux tries to sync
fixed-MTRR state from BP to AP. This implies that Linux sets
SYSCFG[MtrrFixDramEn] and activates those bits.
More important is that (some) systems change these bits in SMM when
ACPI is enabled. Hence it is racy if Linux modifies RdMem/WrMem bits,
too.
(1) The patch modifies an old fix from Bernhard Kaindl to get
suspend/resume working on some Acer Laptops. Bernhard's patch
tried to sync RdMem/WrMem bits of fixed MTRR registers and that
helped on those old Laptops. (Don't ask me why -- can't test it
myself). But this old problem was not the motivation for the
patch. (See http://lkml.org/lkml/2007/4/3/110)
(2) The more important effect is to fix issues on some more current systems.
On those systems Linux panics or just freezes, see
http://bugzilla.kernel.org/show_bug.cgi?id=11541
(and also duplicates of this bug:
http://bugzilla.kernel.org/show_bug.cgi?id=11737
http://bugzilla.kernel.org/show_bug.cgi?id=11714)
The affected systems boot only using acpi=ht, acpi=off or
when the kernel is built with CONFIG_MTRR=n.
The acpi options prevent full enablement of ACPI. Obviously when
ACPI is enabled the BIOS/SMM modfies RdMem/WrMem bits. When
CONFIG_MTRR=y Linux also accesses and modifies those bits when it
needs to sync fixed-MTRRs across cores (Bernhard's fix, see (1)).
How do you synchronize that? You can't. As a consequence Linux
shouldn't touch those bits at all (Rationale are AMD's BKDGs which
recommend to clear the bit that makes RdMem/WrMem accessible).
This is the purpose of this patch. And (so far) this suffices to
fix (1) and (2).
I suggest not to touch RdDram/WrDram bits of fixed-MTRRs and
SYSCFG[MtrrFixDramEn] and to clear SYSCFG[MtrrFixDramModEn] as
suggested by AMD K8, and AMD family 10h/11h BKDGs.
BIOS is expected to do this anyway. This should avoid that
Linux and SMM tread on each other's toes ...
Signed-off-by: Andreas Herrmann <[email protected]>
Cc: [email protected]
Cc: Yinghai Lu <[email protected]>
LKML-Reference: <[email protected]>
Cc: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Signed-off-by: Chris Wright <[email protected]>
---
arch/x86/kernel/cpu/mtrr/generic.c | 51 +++++++++++++++++++++----------------
1 file changed, 30 insertions(+), 21 deletions(-)
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -41,6 +41,32 @@ static int __init mtrr_debug(char *opt)
}
early_param("mtrr.show", mtrr_debug);
+/**
+ * BIOS is expected to clear MtrrFixDramModEn bit, see for example
+ * "BIOS and Kernel Developer's Guide for the AMD Athlon 64 and AMD
+ * Opteron Processors" (26094 Rev. 3.30 February 2006), section
+ * "13.2.1.2 SYSCFG Register": "The MtrrFixDramModEn bit should be set
+ * to 1 during BIOS initalization of the fixed MTRRs, then cleared to
+ * 0 for operation."
+ */
+static inline void k8_check_syscfg_dram_mod_en(void)
+{
+ u32 lo, hi;
+
+ if (!((boot_cpu_data.x86_vendor == X86_VENDOR_AMD) &&
+ (boot_cpu_data.x86 >= 0x0f)))
+ return;
+
+ rdmsr(MSR_K8_SYSCFG, lo, hi);
+ if (lo & K8_MTRRFIXRANGE_DRAM_MODIFY) {
+ printk(KERN_ERR FW_WARN "MTRR: CPU %u: SYSCFG[MtrrFixDramModEn]"
+ " not cleared by BIOS, clearing this bit\n",
+ smp_processor_id());
+ lo &= ~K8_MTRRFIXRANGE_DRAM_MODIFY;
+ mtrr_wrmsr(MSR_K8_SYSCFG, lo, hi);
+ }
+}
+
/*
* Returns the effective MTRR type for the region
* Error returns:
@@ -174,6 +200,8 @@ get_fixed_ranges(mtrr_type * frs)
unsigned int *p = (unsigned int *) frs;
int i;
+ k8_check_syscfg_dram_mod_en();
+
rdmsr(MTRRfix64K_00000_MSR, p[0], p[1]);
for (i = 0; i < 2; i++)
@@ -308,27 +336,10 @@ void mtrr_wrmsr(unsigned msr, unsigned a
}
/**
- * Enable and allow read/write of extended fixed-range MTRR bits on K8 CPUs
- * see AMD publication no. 24593, chapter 3.2.1 for more information
- */
-static inline void k8_enable_fixed_iorrs(void)
-{
- unsigned lo, hi;
-
- rdmsr(MSR_K8_SYSCFG, lo, hi);
- mtrr_wrmsr(MSR_K8_SYSCFG, lo
- | K8_MTRRFIXRANGE_DRAM_ENABLE
- | K8_MTRRFIXRANGE_DRAM_MODIFY, hi);
-}
-
-/**
* set_fixed_range - checks & updates a fixed-range MTRR if it differs from the value it should have
* @msr: MSR address of the MTTR which should be checked and updated
* @changed: pointer which indicates whether the MTRR needed to be changed
* @msrwords: pointer to the MSR values which the MSR should have
- *
- * If K8 extentions are wanted, update the K8 SYSCFG MSR also.
- * See AMD publication no. 24593, chapter 7.8.1, page 233 for more information.
*/
static void set_fixed_range(int msr, bool *changed, unsigned int *msrwords)
{
@@ -337,10 +348,6 @@ static void set_fixed_range(int msr, boo
rdmsr(msr, lo, hi);
if (lo != msrwords[0] || hi != msrwords[1]) {
- if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
- (boot_cpu_data.x86 >= 0x0f && boot_cpu_data.x86 <= 0x11) &&
- ((msrwords[0] | msrwords[1]) & K8_MTRR_RDMEM_WRMEM_MASK))
- k8_enable_fixed_iorrs();
mtrr_wrmsr(msr, msrwords[0], msrwords[1]);
*changed = true;
}
@@ -419,6 +426,8 @@ static int set_fixed_ranges(mtrr_type *
bool changed = false;
int block=-1, range;
+ k8_check_syscfg_dram_mod_en();
+
while (fixed_range_blocks[++block].ranges)
for (range=0; range < fixed_range_blocks[block].ranges; range++)
set_fixed_range(fixed_range_blocks[block].base_msr + range,