Commit-ID: 850055f2e850ef3c1d133e024bc98fa97ff30c48
Gitweb: http://git.kernel.org/tip/850055f2e850ef3c1d133e024bc98fa97ff30c48
Author: Andreas Herrmann <andreas.herrmann3@xxxxxxx>
AuthorDate: Thu, 12 Mar 2009 17:39:37 +0100
Commit: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Fri, 13 Mar 2009 02:55:27 +0100
x86: mtrr: don't modify RdDram/WrDram bits of fixed MTRRs
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.
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 <andreas.herrmann3@xxxxxxx>
Cc: trenn@xxxxxxx
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
LKML-Reference: <20090312163937.GH20716@xxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
arch/x86/kernel/cpu/mtrr/generic.c | 51 +++++++++++++++++++++---------------
1 files changed, 30 insertions(+), 21 deletions(-)
diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 9644035..950c434 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -33,6 +33,32 @@ u64 mtrr_tom2;
struct mtrr_state_type mtrr_state = {};
EXPORT_SYMBOL_GPL(mtrr_state);
+/**
+ * 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:
@@ -166,6 +192,8 @@ 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++)
@@ -306,27 +334,10 @@ void mtrr_wrmsr(unsigned msr, unsigned a, unsigned b)
}
/**
- * 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)
{
@@ -335,10 +346,6 @@ static void set_fixed_range(int msr, bool *changed, unsigned int *msrwords)
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;
}
@@ -426,6 +433,8 @@ static int set_fixed_ranges(mtrr_type * frs)
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,
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|