On Tue, Aug 9, 2011 at 11:00 AM, Ingo Molnar <mingo@xxxxxxx> wrote: > > * Yu, Fenghua <fenghua.yu@xxxxxxxxx> wrote: > >> > -----Original Message----- >> > From: amluto@xxxxxxxxx [mailto:amluto@xxxxxxxxx] On Behalf Of Andrew >> > Lutomirski >> > Sent: Saturday, August 06, 2011 4:32 PM >> > To: Yu, Fenghua >> > Cc: x86@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Matthew Garrett; Len >> > Brown; linux-acpi@xxxxxxxxxxxxxxx; Ingo Molnar >> > Subject: Re: [PATCH v2 1/2] x86: Enable fast strings on Intel if BIOS >> > hasn't already >> > >> > On Sat, Aug 6, 2011 at 3:33 PM, Yu, Fenghua <fenghua.yu@xxxxxxxxx> >> > wrote: >> > >> -----Original Message----- >> > >> From: Andy Lutomirski [mailto:luto@xxxxxxx] >> > >> Sent: Saturday, August 06, 2011 4:43 AM >> > >> To: x86@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx >> > >> Cc: Yu, Fenghua; Matthew Garrett; Len Brown; linux- >> > >> acpi@xxxxxxxxxxxxxxx; Ingo Molnar; Andy Lutomirski >> > >> Subject: [PATCH v2 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. >> > >> >> > >> Signed-off-by: Andy Lutomirski <luto@xxxxxxx> >> > >> --- >> > >> arch/x86/kernel/cpu/intel.c | 25 ++++++++++++++++++++++--- >> > >> 1 files changed, 22 insertions(+), 3 deletions(-) >> > >> >> > >> diff --git a/arch/x86/kernel/cpu/intel.c >> > b/arch/x86/kernel/cpu/intel.c >> > >> index ed6086e..c80ab41 100644 >> > >> --- a/arch/x86/kernel/cpu/intel.c >> > >> +++ b/arch/x86/kernel/cpu/intel.c >> > >> @@ -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)) { >> > >> @@ -118,8 +119,9 @@ 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"); >> > >> >> > >> @@ -130,11 +132,28 @@ 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(KERN_WARNING FW_WARN "CPU #%d: >> > " >> > >> + >> > "IA32_MISC_ENABLE.FAST_STRING_ENABLE " >> > >> + "was not set", c->cpu_index); >> > > This printk is redundant because the same info is dumped in the below >> > printk. Plus it's not firmware's issue if we can not set fast string >> > bit 0 in MISC_ENABLE register. So I don't think FW_WARN is right. >> > >> > Huh? This is the success path -- the patch prints the warning if >> > flipping the bit worked... >> >> Ok. I see. >> >> Still I would suggest to remove this printk. This info will be >> printed on every single CPU if BIOS doesn't enable fast string. > > just do printk_once(). We want to inform the user that something's > going on. Already there in v3. --Andy > > Thanks, > > Ingo > -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
