[PATCH v2 3/8] kvm tools: Allow pausing guests

Sasha Levin
2011-05-30T08:31:41Z

Allow pausing and unpausing guests running on the host.
Pausing a guest means that none of the VCPU threads are running
KVM_RUN until they are unpaused.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
tools/kvm/include/kvm/kvm-cpu.h | 1 +
tools/kvm/include/kvm/kvm.h | 4 +++
tools/kvm/kvm-cpu.c | 20 +++++++++++---
tools/kvm/kvm-run.c | 4 +-
tools/kvm/kvm.c | 54 +++++++++++++++++++++++++++++++++++++++
5 files changed, 76 insertions(+), 7 deletions(-)

diff --git a/tools/kvm/include/kvm/kvm-cpu.h b/tools/kvm/include/kvm/kvm-cpu.h
index b2b6fce..4d99246 100644
--- a/tools/kvm/include/kvm/kvm-cpu.h
+++ b/tools/kvm/include/kvm/kvm-cpu.h
@@ -23,6 +23,7 @@ struct kvm_cpu {
struct kvm_msrs *msrs; /* dynamically allocated */

u8 is_running;
+ u8 paused;
};

struct kvm_cpu *kvm_cpu__init(struct kvm *kvm, unsigned long cpu_id);
diff --git a/tools/kvm/include/kvm/kvm.h b/tools/kvm/include/kvm/kvm.h
index 6a17362..d22a849 100644
--- a/tools/kvm/include/kvm/kvm.h
+++ b/tools/kvm/include/kvm/kvm.h
@@ -12,6 +12,7 @@
#define KVM_32BIT_GAP_START ((1ULL << 32) - KVM_32BIT_GAP_SIZE)

#define SIGKVMEXIT (SIGRTMIN + 0)
+#define SIGKVMPAUSE (SIGRTMIN + 1)

struct kvm {
int sys_fd; /* For system ioctls(), i.e. /dev/kvm */
@@ -50,6 +51,9 @@ bool kvm__emulate_io(struct kvm *kvm, u16 port, void *data, int direction, int s
bool kvm__emulate_mmio(struct kvm *kvm, u64 phys_addr, u8 *data, u32 len, u8 is_write);
bool kvm__register_mmio(u64 phys_addr, u64 phys_addr_len, void (*kvm_mmio_callback_fn)(u64 addr, u8 *data, u32 len, u8 is_write));
bool kvm__deregister_mmio(u64 phys_addr);
+void kvm__pause(void);
+void kvm__continue(void);
+void kvm__notify_paused(void);

/*
* Debugging
diff --git a/tools/kvm/kvm-cpu.c b/tools/kvm/kvm-cpu.c
index de0591f..be0528b 100644
--- a/tools/kvm/kvm-cpu.c
+++ b/tools/kvm/kvm-cpu.c
@@ -383,11 +383,15 @@ void kvm_cpu__run(struct kvm_cpu *vcpu)
die_perror("KVM_RUN failed");
}

-static void kvm_cpu_exit_handler(int signum)
+static void kvm_cpu_signal_handler(int signum)
{
- if (current_kvm_cpu->is_running) {
- current_kvm_cpu->is_running = false;
- pthread_kill(pthread_self(), SIGKVMEXIT);
+ if (signum == SIGKVMEXIT) {
+ if (current_kvm_cpu->is_running) {
+ current_kvm_cpu->is_running = false;
+ pthread_kill(pthread_self(), SIGKVMEXIT);
+ }
+ } else if (signum == SIGKVMPAUSE) {
+ current_kvm_cpu->paused = 1;
}
}

@@ -400,12 +404,18 @@ int kvm_cpu__start(struct kvm_cpu *cpu)

pthread_sigmask(SIG_BLOCK, &sigset, NULL);

- signal(SIGKVMEXIT, kvm_cpu_exit_handler);
+ signal(SIGKVMEXIT, kvm_cpu_signal_handler);
+ signal(SIGKVMPAUSE, kvm_cpu_signal_handler);

kvm_cpu__setup_cpuid(cpu);
kvm_cpu__reset_vcpu(cpu);

for (;;) {
+ if (cpu->paused) {
+ kvm__notify_paused();
+ cpu->paused = 0;
+ }
+
kvm_cpu__run(cpu);

switch (cpu->kvm_run->exit_reason) {
diff --git a/tools/kvm/kvm-run.c b/tools/kvm/kvm-run.c
index 48b8e70..761ac0d 100644
--- a/tools/kvm/kvm-run.c
+++ b/tools/kvm/kvm-run.c
@@ -47,8 +47,8 @@
#define MIN_RAM_SIZE_MB (64ULL)
#define MIN_RAM_SIZE_BYTE (MIN_RAM_SIZE_MB << MB_SHIFT)

-static struct kvm *kvm;
-static struct kvm_cpu *kvm_cpus[KVM_NR_CPUS];
+struct kvm *kvm;
+struct kvm_cpu *kvm_cpus[KVM_NR_CPUS];
__thread struct kvm_cpu *current_kvm_cpu;

static u64 ram_size;
diff --git a/tools/kvm/kvm.c b/tools/kvm/kvm.c
index 1d756e0..54e3203 100644
--- a/tools/kvm/kvm.c
+++ b/tools/kvm/kvm.c
@@ -6,6 +6,8 @@
#include "kvm/interrupt.h"
#include "kvm/mptable.h"
#include "kvm/util.h"
+#include "kvm/mutex.h"
+#include "kvm/kvm-cpu.h"

#include <linux/kvm.h>

@@ -25,6 +27,7 @@
#include <stdio.h>
#include <fcntl.h>
#include <time.h>
+#include <sys/eventfd.h>

#define DEFINE_KVM_EXIT_REASON(reason) [reason] = #reason

@@ -68,6 +71,11 @@ struct {
{ DEFINE_KVM_EXT(KVM_CAP_EXT_CPUID) },
};

+extern struct kvm *kvm;
+extern struct kvm_cpu *kvm_cpus[KVM_NR_CPUS];
+static int pause_event;
+static DEFINE_MUTEX(pause_lock);
+
static bool kvm__supports_extension(struct kvm *kvm, unsigned int extension)
{
int ret;
@@ -575,3 +583,49 @@ void kvm__dump_mem(struct kvm *kvm, unsigned long addr, unsigned long size)
p[n + 4], p[n + 5], p[n + 6], p[n + 7]);
}
}
+
+void kvm__pause(void)
+{
+ int i, paused_vcpus = 0;
+
+ /* Check if the guest is running */
+ if (!kvm_cpus[0] || kvm_cpus[0]->thread == 0)
+ return;
+
+ mutex_lock(&pause_lock);
+
+ pause_event = eventfd(0, 0);
+ if (pause_event < 0)
+ die("Failed creating pause notification event");
+ for (i = 0; i < kvm->nrcpus; i++)
+ pthread_kill(kvm_cpus[i]->thread, SIGKVMPAUSE);
+
+ while (paused_vcpus < kvm->nrcpus) {
+ u64 cur_read;
+
+ if (read(pause_event, &cur_read, sizeof(cur_read)) < 0)
+ die("Failed reading pause event");
+ paused_vcpus += cur_read;
+ }
+ close(pause_event);
+}
+
+void kvm__continue(void)
+{
+ /* Check if the guest is running */
+ if (!kvm_cpus[0] || kvm_cpus[0]->thread == 0)
+ return;
+
+ mutex_unlock(&pause_lock);
+}
+
+void kvm__notify_paused(void)
+{
+ u64 p = 1;
+
+ if (write(pause_event, &p, sizeof(p)) < 0)
+ die("Failed notifying of paused VCPU.");
+
+ mutex_lock(&pause_lock);
+ mutex_unlock(&pause_lock);
+}
--
1.7.5.rc3