Am Montag, 23. Dezember 2013, 19:27:30 schrieb Richard Weinberger: > Currently we do a read, a dummy write and a final read to fetch the error > code. The value from the final read is taken. > This is not the recommended way and leads to corrupted/lost ESR values. > > Intel(c) 64 and IA-32 Architectures Software Developer's Manual, > > Combined Volumes 1, 2ABC, 3ABC, Section 10.5.3 states: > >>Before attempt to read from the ESR, software should first write to it. > > (The value written does not affect the values read subsequently; > only zero may be written in x2APIC mode.) This write clears > any previously logged errors and updates the ESR with any errors > detected since the last write to the ESR. > This write also rearms the APIC error interrupt triggering mechanism.<< > > This patch removes the first read such that we are conform with the manual. > > On my (very old) Pentium MMX SMP system this patch fixes the issue that > APIC errors a) are not always reported and b) are reported with false > error numbers. > > Signed-off-by: Richard Weinberger <[email protected]> > --- > arch/x86/kernel/apic/apic.c | 17 ++++++++--------- > 1 file changed, 8 insertions(+), 9 deletions(-) > > diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c > index d278736..4ec1dd6 100644 > --- a/arch/x86/kernel/apic/apic.c > +++ b/arch/x86/kernel/apic/apic.c > @@ -1968,7 +1968,7 @@ __visible void smp_trace_spurious_interrupt(struct > pt_regs *regs) */ > static inline void __smp_error_interrupt(struct pt_regs *regs) > { > - u32 v0, v1; > + u32 v; > u32 i = 0; > static const char * const error_interrupt_reason[] = { > "Send CS error", /* APIC Error Bit 0 */ > @@ -1982,21 +1982,20 @@ static inline void __smp_error_interrupt(struct > pt_regs *regs) }; > > /* First tickle the hardware, only then report what went on. -- REW */ > - v0 = apic_read(APIC_ESR); > apic_write(APIC_ESR, 0); > - v1 = apic_read(APIC_ESR); > + v = apic_read(APIC_ESR); > ack_APIC_irq(); > atomic_inc(&irq_err_count); > > - apic_printk(APIC_DEBUG, KERN_DEBUG "APIC error on CPU%d: %02x(%02x)", > - smp_processor_id(), v0 , v1); > + apic_printk(APIC_DEBUG, KERN_DEBUG "APIC error on CPU%d: %02x", > + smp_processor_id(), v); > > - v1 = v1 & 0xff; > - while (v1) { > - if (v1 & 0x1) > + v &= 0xff; > + while (v) { > + if (v & 0x1) > apic_printk(APIC_DEBUG, KERN_CONT " : %s", error_interrupt_reason[i]); > i++; > - v1 >>= 1; > + v >>= 1; > } > > apic_printk(APIC_DEBUG, KERN_CONT "\n");
Any comments on this? Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
