13 files changed, 71 insertions, 7 deletions

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index bde494654bcc..6a79314bc1df 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -148,6 +148,7 @@ struct kvm_vm_stat {
 };
 
 struct kvm_vcpu_stat {
+        u32 halt_successful_poll;
         u32 halt_wakeup;
 };
 
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 2c49aa4ac818..8efde89613f2 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -165,6 +165,7 @@ struct kvm_vm_stat {
 };
 
 struct kvm_vcpu_stat {
+        u32 halt_successful_poll;
         u32 halt_wakeup;
 };
 
diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index f2c249796ea8..ac4fc716062b 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -120,6 +120,7 @@ struct kvm_vcpu_stat {
         u32 resvd_inst_exits;
         u32 break_inst_exits;
         u32 flush_dcache_exits;
+        u32 halt_successful_poll;
         u32 halt_wakeup;
 };
 
diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index e97b90784031..c9eccf5df912 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -49,6 +49,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
         { "resvd_inst",   VCPU_STAT(resvd_inst_exits),   KVM_STAT_VCPU },
         { "break_inst",   VCPU_STAT(break_inst_exits),   KVM_STAT_VCPU },
         { "flush_dcache", VCPU_STAT(flush_dcache_exits), KVM_STAT_VCPU },
+        { "halt_successful_poll", VCPU_STAT(halt_successful_poll), KVM_STAT_VCPU },
         { "halt_wakeup",  VCPU_STAT(halt_wakeup),        KVM_STAT_VCPU },
         {NULL}
 };
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index 7efd666a3fa7..8ef05121d3cd 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -107,6 +107,7 @@ struct kvm_vcpu_stat {
         u32 emulated_inst_exits;
         u32 dec_exits;
         u32 ext_intr_exits;
+        u32 halt_successful_poll;
         u32 halt_wakeup;
         u32 dbell_exits;
         u32 gdbell_exits;
diff --git a/arch/powerpc/kvm/book3s.c b/arch/powerpc/kvm/book3s.c
index 888bf466d8c6..cfbcdc654201 100644
--- a/arch/powerpc/kvm/book3s.c
+++ b/arch/powerpc/kvm/book3s.c
@@ -52,6 +52,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
         { "dec",         VCPU_STAT(dec_exits) },
         { "ext_intr",    VCPU_STAT(ext_intr_exits) },
         { "queue_intr",  VCPU_STAT(queue_intr) },
+        { "halt_successful_poll", VCPU_STAT(halt_successful_poll), },
         { "halt_wakeup", VCPU_STAT(halt_wakeup) },
         { "pf_storage",  VCPU_STAT(pf_storage) },
         { "sp_storage",  VCPU_STAT(sp_storage) },
diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
index 9b55dec2d6cc..6c1316a15a27 100644
--- a/arch/powerpc/kvm/booke.c
+++ b/arch/powerpc/kvm/booke.c
@@ -62,6 +62,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
         { "inst_emu",   VCPU_STAT(emulated_inst_exits) },
         { "dec",        VCPU_STAT(dec_exits) },
         { "ext_intr",   VCPU_STAT(ext_intr_exits) },
+        { "halt_successful_poll", VCPU_STAT(halt_successful_poll) },
         { "halt_wakeup", VCPU_STAT(halt_wakeup) },
         { "doorbell", VCPU_STAT(dbell_exits) },
         { "guest doorbell", VCPU_STAT(gdbell_exits) },
diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
index d1ecc7fd0579..f79058e3fd98 100644
--- a/arch/s390/include/asm/kvm_host.h
+++ b/arch/s390/include/asm/kvm_host.h
@@ -196,6 +196,7 @@ struct kvm_vcpu_stat {
         u32 exit_stop_request;
         u32 exit_validity;
         u32 exit_instruction;
+        u32 halt_successful_poll;
         u32 halt_wakeup;
         u32 instruction_lctl;
         u32 instruction_lctlg;
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index b2371c0fd1f8..1dbab2340a66 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -51,6 +51,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
         { "exit_instruction", VCPU_STAT(exit_instruction) },
         { "exit_program_interruption", VCPU_STAT(exit_program_interruption) },
         { "exit_instr_and_program_int", VCPU_STAT(exit_instr_and_program) },
+        { "halt_successful_poll", VCPU_STAT(halt_successful_poll) },
         { "halt_wakeup", VCPU_STAT(halt_wakeup) },
         { "instruction_lctlg", VCPU_STAT(instruction_lctlg) },
         { "instruction_lctl", VCPU_STAT(instruction_lctl) },
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 848947ac6ade..a236e39cc385 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -655,6 +655,7 @@ struct kvm_vcpu_stat {
         u32 irq_window_exits;
         u32 nmi_window_exits;
         u32 halt_exits;
+        u32 halt_successful_poll;
         u32 halt_wakeup;
         u32 request_irq_exits;
         u32 irq_exits;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1373e04e1f19..bd7a70be41b3 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -145,6 +145,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
         { "irq_window", VCPU_STAT(irq_window_exits) },
         { "nmi_window", VCPU_STAT(nmi_window_exits) },
         { "halt_exits", VCPU_STAT(halt_exits) },
+        { "halt_successful_poll", VCPU_STAT(halt_successful_poll) },
         { "halt_wakeup", VCPU_STAT(halt_wakeup) },
         { "hypercalls", VCPU_STAT(hypercalls) },
         { "request_irq", VCPU_STAT(request_irq_exits) },
diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
index 6edf1f2028cd..6bfe7eec1c2c 100644
--- a/include/trace/events/kvm.h
+++ b/include/trace/events/kvm.h
@@ -37,6 +37,25 @@ TRACE_EVENT(kvm_userspace_exit,
                   __entry->errno < 0 ? -__entry->errno : __entry->reason)
 );
 
+TRACE_EVENT(kvm_vcpu_wakeup,
+            TP_PROTO(__u64 ns, bool waited),
+            TP_ARGS(ns, waited),
+
+        TP_STRUCT__entry(
+                __field(        __u64,          ns              )
+                __field(        bool,           waited          )
+        ),
+
+        TP_fast_assign(
+                __entry->ns             = ns;
+                __entry->waited         = waited;
+        ),
+
+        TP_printk("%s time %lld ns",
+                  __entry->waited ? "wait" : "poll",
+                  __entry->ns)
+);
+
 #if defined(CONFIG_HAVE_KVM_IRQFD)
 TRACE_EVENT(kvm_set_irq,
         TP_PROTO(unsigned int gsi, int level, int irq_source_id),
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 0c281760a1c5..32449e0e9aa8 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -66,6 +66,9 @@
 MODULE_AUTHOR("Qumranet");
 MODULE_LICENSE("GPL");
 
+unsigned int halt_poll_ns = 0;
+module_param(halt_poll_ns, uint, S_IRUGO | S_IWUSR);
+
 /*
  * Ordering of locks:
  *
@@ -1813,29 +1816,60 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(mark_page_dirty);
 
+static int kvm_vcpu_check_block(struct kvm_vcpu *vcpu)
+{
+        if (kvm_arch_vcpu_runnable(vcpu)) {
+                kvm_make_request(KVM_REQ_UNHALT, vcpu);
+                return -EINTR;
+        }
+        if (kvm_cpu_has_pending_timer(vcpu))
+                return -EINTR;
+        if (signal_pending(current))
+                return -EINTR;
+
+        return 0;
+}
+
 /*
  * The vCPU has executed a HLT instruction with in-kernel mode enabled.
  */
 void kvm_vcpu_block(struct kvm_vcpu *vcpu)
 {
+        ktime_t start, cur;
         DEFINE_WAIT(wait);
+        bool waited = false;
+
+        start = cur = ktime_get();
+        if (halt_poll_ns) {
+                ktime_t stop = ktime_add_ns(ktime_get(), halt_poll_ns);
+                do {
+                        /*
+                         * This sets KVM_REQ_UNHALT if an interrupt
+                         * arrives.
+                         */
+                        if (kvm_vcpu_check_block(vcpu) < 0) {
+                                ++vcpu->stat.halt_successful_poll;
+                                goto out;
+                        }
+                        cur = ktime_get();
+                } while (single_task_running() && ktime_before(cur, stop));
+        }
 
         for (;;) {
                 prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
 
-                if (kvm_arch_vcpu_runnable(vcpu)) {
-                        kvm_make_request(KVM_REQ_UNHALT, vcpu);
-                        break;
-                }
-                if (kvm_cpu_has_pending_timer(vcpu))
-                        break;
-                if (signal_pending(current))
+                if (kvm_vcpu_check_block(vcpu) < 0)
                         break;
 
+                waited = true;
                 schedule();
         }
 
         finish_wait(&vcpu->wq, &wait);
+        cur = ktime_get();
+
+out:
+        trace_kvm_vcpu_wakeup(ktime_to_ns(cur) - ktime_to_ns(start), waited);
 }
 EXPORT_SYMBOL_GPL(kvm_vcpu_block);