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Subject[tip:x86/urgent] x86, amd: Restrict usage of c1e_idle()
Commit-ID:  035a02c1e1de31888e8b6adac0ff667971ac04db
Gitweb: http://git.kernel.org/tip/035a02c1e1de31888e8b6adac0ff667971ac04db
Author: Andreas Herrmann <andreas.herrmann3@amd.com>
AuthorDate: Fri, 19 Mar 2010 12:09:22 +0100
Committer: H. Peter Anvin <hpa@zytor.com>
CommitDate: Fri, 19 Mar 2010 14:43:36 -0700

x86, amd: Restrict usage of c1e_idle()

Currently c1e_idle returns true for all CPUs greater than or equal to
family 0xf model 0x40. This covers too many CPUs.

Meanwhile a respective erratum for the underlying problem was filed
(#400). This patch adds the logic to check whether erratum #400
applies to a given CPU.
Especially for CPUs where SMI/HW triggered C1e is not supported,
c1e_idle() doesn't need to be used. We can check this by looking at
the respective OSVW bit for erratum #400.

Cc: <stable@kernel.org> # .32.x .33.x
Signed-off-by: Andreas Herrmann <andreas.herrmann3@amd.com>
LKML-Reference: <20100319110922.GA19614@alberich.amd.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
---
arch/x86/include/asm/msr-index.h | 2 ++
arch/x86/kernel/process.c | 32 ++++++++++++++++++++++++--------
2 files changed, 26 insertions(+), 8 deletions(-)
diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 1cd58cd..4604e6a 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -105,6 +105,8 @@
#define MSR_AMD64_PATCH_LEVEL 0x0000008b
#define MSR_AMD64_NB_CFG 0xc001001f
#define MSR_AMD64_PATCH_LOADER 0xc0010020
+#define MSR_AMD64_OSVW_ID_LENGTH 0xc0010140
+#define MSR_AMD64_OSVW_STATUS 0xc0010141
#define MSR_AMD64_IBSFETCHCTL 0xc0011030
#define MSR_AMD64_IBSFETCHLINAD 0xc0011031
#define MSR_AMD64_IBSFETCHPHYSAD 0xc0011032
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index ad95406..28ad9f4 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -526,21 +526,37 @@ static int __cpuinit mwait_usable(const struct cpuinfo_x86 *c)
}

/*
- * Check for AMD CPUs, which have potentially C1E support
+ * Check for AMD CPUs, where APIC timer interrupt does not wake up CPU from C1e.
+ * For more information see
+ * - Erratum #400 for NPT family 0xf and family 0x10 CPUs
+ * - Erratum #365 for family 0x11 (not affected because C1e not in use)
*/
static int __cpuinit check_c1e_idle(const struct cpuinfo_x86 *c)
{
+ u64 val;
if (c->x86_vendor != X86_VENDOR_AMD)
- return 0;
-
- if (c->x86 < 0x0F)
- return 0;
+ goto no_c1e_idle;

/* Family 0x0f models < rev F do not have C1E */
- if (c->x86 == 0x0f && c->x86_model < 0x40)
- return 0;
+ if (c->x86 == 0x0F && c->x86_model >= 0x40)
+ return 1;

- return 1;
+ if (c->x86 == 0x10) {
+ /*
+ * check OSVW bit for CPUs that are not affected
+ * by erratum #400
+ */
+ rdmsrl(MSR_AMD64_OSVW_ID_LENGTH, val);
+ if (val >= 2) {
+ rdmsrl(MSR_AMD64_OSVW_STATUS, val);
+ if (!(val & BIT(1)))
+ goto no_c1e_idle;
+ }
+ return 1;
+ }
+
+no_c1e_idle:
+ return 0;
}

static cpumask_var_t c1e_mask;

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