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x86: add x2apic_wrmsr_fence() to x2apic flush tlb paths 

Impact: optimize APIC IPI related barriers

Uncached MMIO accesses for xapic are inherently serializing and hence
we don't need explicit barriers for xapic IPI paths.

x2apic MSR writes/reads don't have serializing semantics and hence need
a serializing instruction or mfence, to make all the previous memory
stores globally visisble before the x2apic msr write for IPI.

Add x2apic_wrmsr_fence() in flush tlb path to x2apic specific paths.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: "steiner@sgi.com" <steiner@sgi.com>
Cc: Nick Piggin <npiggin@suse.de>
LKML-Reference: <1237313814.27006.203.camel@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Suresh Siddha 2009-03-17 10:16:54 -08:00 committed by Ingo Molnar
parent fa4b57cc04
commit ce4e240c27
4 changed files with 22 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
arch/x86/include/asm/apic.h
View File

@ -108,6 +108,16 @@ extern void native_apic_icr_write(u32 low, u32 id);
extern u64 native_apic_icr_read(void);
#ifdef CONFIG_X86_X2APIC
/*
* Make previous memory operations globally visible before
* sending the IPI through x2apic wrmsr. We need a serializing instruction or
* mfence for this.
*/
static inline void x2apic_wrmsr_fence(void)
{
asm volatile("mfence" : : : "memory");
}
static inline void native_apic_msr_write(u32 reg, u32 v)
{
if (reg == APIC_DFR || reg == APIC_ID || reg == APIC_LDR ||

6
arch/x86/kernel/apic/x2apic_cluster.c
View File

@ -57,6 +57,8 @@ static void x2apic_send_IPI_mask(const struct cpumask *mask, int vector)
unsigned long query_cpu;
unsigned long flags;
x2apic_wrmsr_fence();
local_irq_save(flags);
for_each_cpu(query_cpu, mask) {
__x2apic_send_IPI_dest(
@ -73,6 +75,8 @@ static void
unsigned long query_cpu;
unsigned long flags;
x2apic_wrmsr_fence();
local_irq_save(flags);
for_each_cpu(query_cpu, mask) {
if (query_cpu == this_cpu)
@ -90,6 +94,8 @@ static void x2apic_send_IPI_allbutself(int vector)
unsigned long query_cpu;
unsigned long flags;
x2apic_wrmsr_fence();
local_irq_save(flags);
for_each_online_cpu(query_cpu) {
if (query_cpu == this_cpu)

6
arch/x86/kernel/apic/x2apic_phys.c
View File

@ -58,6 +58,8 @@ static void x2apic_send_IPI_mask(const struct cpumask *mask, int vector)
unsigned long query_cpu;
unsigned long flags;
x2apic_wrmsr_fence();
local_irq_save(flags);
for_each_cpu(query_cpu, mask) {
__x2apic_send_IPI_dest(per_cpu(x86_cpu_to_apicid, query_cpu),
@ -73,6 +75,8 @@ static void
unsigned long query_cpu;
unsigned long flags;
x2apic_wrmsr_fence();
local_irq_save(flags);
for_each_cpu(query_cpu, mask) {
if (query_cpu != this_cpu)
@ -89,6 +93,8 @@ static void x2apic_send_IPI_allbutself(int vector)
unsigned long query_cpu;
unsigned long flags;
x2apic_wrmsr_fence();
local_irq_save(flags);
for_each_online_cpu(query_cpu) {
if (query_cpu == this_cpu)

5
arch/x86/mm/tlb.c
View File

@ -186,11 +186,6 @@ static void flush_tlb_others_ipi(const struct cpumask *cpumask,
cpumask_andnot(to_cpumask(f->flush_cpumask),
cpumask, cpumask_of(smp_processor_id()));
/*
* Make the above memory operations globally visible before
* sending the IPI.
*/
smp_mb();
/*
* We have to send the IPI only to
* CPUs affected.