[PATCH v6 2/2] KVM: Using workqueue for WBINVD

Sheng Yang
2010-06-30T04:27:15Z

It would buy us the ability to schedule compared to smp_call_function().

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---

But I am not sure if it worth the complexity. Anyway WBINVD itself can't be
interrupted, so the benefit should come to the caller cpu I think. And that
would extended the waiting time for the caller cpu, for we still need to wait
other cpus to complete their works.

arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/x86.c | 35 ++++++++++++++++++++++++++++-------
2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 2bda624..6e0b793 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -16,6 +16,7 @@
#include <linux/mmu_notifier.h>
#include <linux/tracepoint.h>
#include <linux/cpumask.h>
+#include <linux/workqueue.h>

#include <linux/kvm.h>
#include <linux/kvm_para.h>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index eea75f5..13f7c88 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -153,6 +153,9 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {

u64 __read_mostly host_xcr0;

+static struct workqueue_struct *wbinvd_wq;
+static DEFINE_PER_CPU(struct work_struct, wbinvd_work);
+
static inline u32 bit(int bitno)
{
return 1 << (bitno & 31);
@@ -1783,7 +1786,7 @@ out:
return r;
}

-static void wbinvd_ipi(void *garbage)
+static void wbinvd_do_work(struct work_struct *work)
{
wbinvd();
}
@@ -1800,9 +1803,11 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
if (need_emulate_wbinvd(vcpu)) {
if (kvm_x86_ops->has_wbinvd_exit())
cpumask_set_cpu(cpu, vcpu->arch.wbinvd_dirty_mask);
- else if (vcpu->cpu != -1 && vcpu->cpu != cpu)
- smp_call_function_single(vcpu->cpu,
- wbinvd_ipi, NULL, 1);
+ else if (vcpu->cpu != -1 && vcpu->cpu != cpu) {
+ queue_work_on(vcpu->cpu, wbinvd_wq,
+ &per_cpu(wbinvd_work, vcpu->cpu));
+ flush_workqueue(wbinvd_wq);
+ }
}

kvm_x86_ops->vcpu_load(vcpu, cpu);
@@ -3672,12 +3677,16 @@ int emulate_invlpg(struct kvm_vcpu *vcpu, gva_t address)

int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu)
{
+ int cpu;
+
if (!need_emulate_wbinvd(vcpu))
return X86EMUL_CONTINUE;

if (kvm_x86_ops->has_wbinvd_exit()) {
- smp_call_function_many(vcpu->arch.wbinvd_dirty_mask,
- wbinvd_ipi, NULL, 1);
+ for_each_cpu(cpu, vcpu->arch.wbinvd_dirty_mask)
+ queue_work_on(cpu, wbinvd_wq,
+ &per_cpu(wbinvd_work, cpu));
+ flush_workqueue(wbinvd_wq);
cpumask_clear(vcpu->arch.wbinvd_dirty_mask);
}
wbinvd();
@@ -4179,7 +4188,7 @@ EXPORT_SYMBOL_GPL(kvm_after_handle_nmi);

int kvm_arch_init(void *opaque)
{
- int r;
+ int r, cpu;
struct kvm_x86_ops *ops = (struct kvm_x86_ops *)opaque;

if (kvm_x86_ops) {
@@ -4218,6 +4227,16 @@ int kvm_arch_init(void *opaque)
if (cpu_has_xsave)
host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);

+ for_each_possible_cpu(cpu) {
+ INIT_WORK(&per_cpu(wbinvd_work, cpu), wbinvd_do_work);
+ }
+
+ wbinvd_wq = create_workqueue("kvm_wbinvd");
+ if (!wbinvd_wq) {
+ r = -ENOMEM;
+ goto out;
+ }
+
return 0;

out:
@@ -4226,6 +4245,8 @@ out:

void kvm_arch_exit(void)
{
+ destroy_workqueue(wbinvd_wq);
+
perf_unregister_guest_info_callbacks(&kvm_guest_cbs);

if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
--
1.7.0.1