[RFC PATCH v1 1/2] kvm: Implement guest_exit_last_time()

Leonardo Bras
2024-03-28T17:20:06Z

Keep track of the last time a cpu ran guest_exit(), and provide a helper to
make this information available to other files.

Signed-off-by: Leonardo Bras <leobras@redhat.com>
---
include/linux/kvm_host.h | 13 +++++++++++++
virt/kvm/kvm_main.c | 3 +++
2 files changed, 16 insertions(+)

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 48f31dcd318a..be90d83d631a 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -470,31 +470,44 @@ static __always_inline void guest_state_enter_irqoff(void)
{
instrumentation_begin();
trace_hardirqs_on_prepare();
lockdep_hardirqs_on_prepare();
instrumentation_end();

guest_context_enter_irqoff();
lockdep_hardirqs_on(CALLER_ADDR0);
}

+DECLARE_PER_CPU(unsigned long, kvm_last_guest_exit);
+
+/*
+ * Returns time (jiffies) for the last guest exit in current cpu
+ */
+static inline unsigned long guest_exit_last_time(void)
+{
+ return this_cpu_read(kvm_last_guest_exit);
+}
+
/*
* Exit guest context and exit an RCU extended quiescent state.
*
* Between guest_context_enter_irqoff() and guest_context_exit_irqoff() it is
* unsafe to use any code which may directly or indirectly use RCU, tracing
* (including IRQ flag tracing), or lockdep. All code in this period must be
* non-instrumentable.
*/
static __always_inline void guest_context_exit_irqoff(void)
{
context_tracking_guest_exit();
+
+ /* Keeps track of last guest exit */
+ this_cpu_write(kvm_last_guest_exit, jiffies);
}

/*
* Stop accounting time towards a guest.
* Must be called after exiting guest context.
*/
static __always_inline void guest_timing_exit_irqoff(void)
{
instrumentation_begin();
/* Flush the guest cputime we spent on the guest */
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index fb49c2a60200..732b1ab43ac9 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -103,20 +103,23 @@ EXPORT_SYMBOL_GPL(halt_poll_ns_shrink);
*/

DEFINE_MUTEX(kvm_lock);
LIST_HEAD(vm_list);

static struct kmem_cache *kvm_vcpu_cache;

static __read_mostly struct preempt_ops kvm_preempt_ops;
static DEFINE_PER_CPU(struct kvm_vcpu *, kvm_running_vcpu);

+DEFINE_PER_CPU(unsigned long, kvm_last_guest_exit);
+EXPORT_SYMBOL_GPL(kvm_last_guest_exit);
+
struct dentry *kvm_debugfs_dir;
EXPORT_SYMBOL_GPL(kvm_debugfs_dir);

static const struct file_operations stat_fops_per_vm;

static long kvm_vcpu_ioctl(struct file *file, unsigned int ioctl,
unsigned long arg);
#ifdef CONFIG_KVM_COMPAT
static long kvm_vcpu_compat_ioctl(struct file *file, unsigned int ioctl,
unsigned long arg);
--
2.44.0