Forcibly enable some MISC_ENABLE features on Intel
v4 cover Forcibly enable some MISC_ENABLE features on Intel
Intel allows BIOS or the OS to enable or disable some CPU fueatures via IA32_MISC_ENABLE. I have machines that don't enable fast strings or monitor/mwait in BIOS, so do it on bootup instead.
Changes from v3:
- Don't display CPU index (and therefore don't break !SMP build)
- Don't display "Failed to enable..." when kmemcheck is on
Changes from v2:
- Don't linebreak printk messages (for ease of grepping)
- Use printk_once
- Update the "Disabled fast string operations" message
Changes from v1:
- Display FW_WARN messages.
- Don't change the kmemcheck message.
- Improve the fast string comment.
- Improve the changelogs.
Andy Lutomirski (2):
x86: Enable fast strings on Intel if BIOS hasn't already
x86: Enable monitor/mwait on Intel if BIOS hasn't already
arch/x86/kernel/cpu/intel.c | 51 ++++++++++++++++++++++++++++++++++++++---- 1 files changed, 46 insertions(+), 5 deletions(-)
Signature · 1 line
1.7.6
PATCH v4 1/2 x86: Enable fast strings on Intel if BIOS hasn't already
Intel SDM volume 3A, 8.4.2 says:
Software can disable fast-string operation by clearing the fast-string-enable bit (bit 0) of IA32_MISC_ENABLE MSR. However, Intel recomments that system software always enable fast-string operation.
The Intel DQ67SW board (with latest BIOS) disables fast string operations if TXT is enabled. A Lenovo X220 disables it regardless of TXT setting. I doubt I'm the only person with a dumb BIOS like this.
--- arch/x86/kernel/cpu/intel.c | 28 +++++++++++++++++++++++----- 1 files changed, 23 insertions(+), 5 deletions(-)
arch/x86/kernel/cpu/intel.c +23 -5
@@ -30,6 +30,7 @@static void __cpuinit early_init_intel (struct cpuinfo_x86 *c) {u64 misc_enable; +bool allow_fast_string = true;/* Unmask CPUID levels if masked: */ if (c->x86 >6 || (c->x86 ==6 && c->x86_model >=0xd )) {
@@ -118,10 +119,11 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c)* (model 2) with the same problem. */ if (c->x86 ==15 ) { -rdmsrl (MSR_IA32_MISC_ENABLE , misc_enable); + allow_fast_string = false; +rdmsrl (MSR_IA32_MISC_ENABLE , misc_enable);if (misc_enable &MSR_IA32_MISC_ENABLE_FAST_STRING ) { -printk (KERN_INFO "kmemcheck: Disabling fast string operations\n" ); +printk_once (KERN_INFO "kmemcheck: Disabling fast string operations\n" ); misc_enable &= ~MSR_IA32_MISC_ENABLE_FAST_STRING ;wrmsrl (MSR_IA32_MISC_ENABLE , misc_enable);
@@ -130,13 +132,29 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c)#endif /* -* If fast string is not enabled in IA32_MISC_ENABLE for any reason, -* clear the fast string and enhanced fast string CPU capabilities. +* If BIOS didn't enable fast string operation, try to enable +* it ourselves. If that fails, then clear the fast string +* and enhanced fast string CPU capabilities. */ if (c->x86 >6 || (c->x86 ==6 && c->x86_model >=0xd )) {rdmsrl (MSR_IA32_MISC_ENABLE , misc_enable); + +if (allow_fast_string && + !(misc_enable &MSR_IA32_MISC_ENABLE_FAST_STRING )) { + misc_enable |=MSR_IA32_MISC_ENABLE_FAST_STRING ; +wrmsr_safe (MSR_IA32_MISC_ENABLE , (u32 )misc_enable, + (u32)(misc_enable >>32 )); + +/* Re-read to make sure it stuck. */ +rdmsrl (MSR_IA32_MISC_ENABLE , misc_enable); + +if (misc_enable &MSR_IA32_MISC_ENABLE_FAST_STRING ) + printk_once(KERN_INFO FW_WARN "IA32_MISC_ENABLE.FAST_STRING_ENABLE was not set\n"); + } +if (!(misc_enable &MSR_IA32_MISC_ENABLE_FAST_STRING )) { -printk (KERN_INFO "Disabled fast string operations\n" ); +if (allow_fast_string) +printk_once (KERN_INFO "Failed to enable fast string operations\n" );setup_clear_cpu_cap (X86_FEATURE_REP_GOOD );setup_clear_cpu_cap (X86_FEATURE_ERMS ); }
Signature · 1 line
1.7.6
RE: [PATCH v4 1/2] x86: Enable fast strings on Intel if BIOS hasn't already
Quoted 16 lines
-----Original Message-----
From: Andy Lutomirski [mailto:[email protected]]
Sent: Wednesday, August 17, 2011 7:03 AM
To: [email protected]; [email protected]
Cc: Yu, Fenghua; Matthew Garrett; Len Brown; linux- [email protected]; Ingo Molnar; Andy Lutomirski
Subject: [PATCH v4 1/2] x86: Enable fast strings on Intel if BIOS hasn't alreadyIntel SDM volume 3A, 8.4.2 says:
Software can disable fast-string operation by clearing the fast-string-enable bit (bit 0) of
IA32_MISC_ENABLEMSR. However, Intel recomments that system software always enable fast-string operation.
Quoted 6 lines
The Intel DQ67SW board (with latest BIOS) disables fast string operations if TXT is enabled. A Lenovo X220 disables it regardless of TXT setting. I doubt I'm the only person with a dumb BIOS like this.
Signed-off-by Andy Lutomirski <[email protected]>
PATCH v4 2/2 x86: Enable monitor/mwait on Intel if BIOS hasn't already
In reply to Andy LutomirskiMy Intel DQ67SW (latest BIOS) disables monitor/mwait on the boot CPU if TXT is enabled. We're lucky that the system works at all, since the feature is still enabled on other CPUs.
The obvious fix is to just re-enable it ourselves.
--- arch/x86/kernel/cpu/intel.c | 23 +++++++++++++++++++++++ 1 files changed, 23 insertions(+), 0 deletions(-)
arch/x86/kernel/cpu/intel.c +23 -0
@@ -492,6 +492,29 @@ static void __cpuinit init_intel(struct cpuinfo_x86 *c)wrmsrl (MSR_IA32_ENERGY_PERF_BIAS , epb); } } + +/* Enable monitor/mwait if BIOS didn't do it for us. */ +if (!cpu_has (c,X86_FEATURE_MWAIT ) &&cpu_has (c,X86_FEATURE_XMM3 ) + && c->x86 >=6 && !(c->x86 ==6 && c->x86_model <0x1c ) + && !(c->x86 ==0xf && c->x86_model <3 )) { +u64 misc_enable; +rdmsrl (MSR_IA32_MISC_ENABLE , misc_enable); + misc_enable |=MSR_IA32_MISC_ENABLE_MWAIT ; + +/* +* Some non-SSE3 cpus will #GP. We check for that, +* but it can't hurt to be safe. +*/ +wrmsr_safe (MSR_IA32_MISC_ENABLE , (u32 )misc_enable, + (u32)(misc_enable >>32 )); + +/* Re-read monitor capability. */ +if (cpuid_ecx (1 ) &0x8 ) { +set_cpu_cap (c,X86_FEATURE_MWAIT ); + + printk(KERN_WARNING FW_WARN "IA32_MISC_ENABLE.ENABLE_MONITOR_FSM was not set\n"); + } + } }#ifdef CONFIG_X86_32
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1.7.6