* 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. 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
