diff options
Diffstat (limited to 'drivers/xen/time.c')
-rw-r--r-- | drivers/xen/time.c | 88 |
1 files changed, 88 insertions, 0 deletions
diff --git a/drivers/xen/time.c b/drivers/xen/time.c new file mode 100644 index 000000000..71078425c --- /dev/null +++ b/drivers/xen/time.c @@ -0,0 +1,88 @@ +/* + * Xen stolen ticks accounting. + */ +#include <linux/kernel.h> +#include <linux/kernel_stat.h> +#include <linux/math64.h> +#include <linux/gfp.h> + +#include <asm/xen/hypervisor.h> +#include <asm/xen/hypercall.h> + +#include <xen/events.h> +#include <xen/features.h> +#include <xen/interface/xen.h> +#include <xen/interface/vcpu.h> +#include <xen/xen-ops.h> + +/* runstate info updated by Xen */ +static DEFINE_PER_CPU(struct vcpu_runstate_info, xen_runstate); + +/* return an consistent snapshot of 64-bit time/counter value */ +static u64 get64(const u64 *p) +{ + u64 ret; + + if (BITS_PER_LONG < 64) { + u32 *p32 = (u32 *)p; + u32 h, l, h2; + + /* + * Read high then low, and then make sure high is + * still the same; this will only loop if low wraps + * and carries into high. + * XXX some clean way to make this endian-proof? + */ + do { + h = READ_ONCE(p32[1]); + l = READ_ONCE(p32[0]); + h2 = READ_ONCE(p32[1]); + } while(h2 != h); + + ret = (((u64)h) << 32) | l; + } else + ret = READ_ONCE(*p); + + return ret; +} + +/* + * Runstate accounting + */ +void xen_get_runstate_snapshot(struct vcpu_runstate_info *res) +{ + u64 state_time; + struct vcpu_runstate_info *state; + + BUG_ON(preemptible()); + + state = this_cpu_ptr(&xen_runstate); + + /* + * The runstate info is always updated by the hypervisor on + * the current CPU, so there's no need to use anything + * stronger than a compiler barrier when fetching it. + */ + do { + state_time = get64(&state->state_entry_time); + *res = READ_ONCE(*state); + } while (get64(&state->state_entry_time) != state_time); +} + +/* return true when a vcpu could run but has no real cpu to run on */ +bool xen_vcpu_stolen(int vcpu) +{ + return per_cpu(xen_runstate, vcpu).state == RUNSTATE_runnable; +} + +void xen_setup_runstate_info(int cpu) +{ + struct vcpu_register_runstate_memory_area area; + + area.addr.v = &per_cpu(xen_runstate, cpu); + + if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area, + cpu, &area)) + BUG(); +} + |