@@ -4057,7 +4057,7 @@
prediction) vulnerability. System may allow data
leaks with this option.
- no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,EARLY] Disable
+ no-steal-acc [X86,PV_OPS,ARM64,PPC/PSERIES,RISCV,LOONGARCH,EARLY] Disable
paravirtualized steal time accounting. steal time is
computed, but won't influence scheduler behaviour
@@ -641,6 +641,17 @@ config PARAVIRT
over full virtualization. However, when run without a hypervisor
the kernel is theoretically slower and slightly larger.
+config PARAVIRT_TIME_ACCOUNTING
+ bool "Paravirtual steal time accounting"
+ select PARAVIRT
+ help
+ Select this option to enable fine granularity task steal time
+ accounting. Time spent executing other tasks in parallel with
+ the current vCPU is discounted from the vCPU power. To account for
+ that, there can be a small performance impact.
+
+ If in doubt, say N here.
+
endmenu
config ARCH_SELECT_MEMORY_MODEL
@@ -18,6 +18,7 @@ static inline u64 paravirt_steal_clock(int cpu)
}
int __init pv_ipi_init(void);
+int __init pv_time_init(void);
#else
@@ -26,5 +27,9 @@ static inline int pv_ipi_init(void)
return 0;
}
+static inline int pv_time_init(void)
+{
+ return 0;
+}
#endif // CONFIG_PARAVIRT
#endif
@@ -4,11 +4,14 @@
#include <linux/interrupt.h>
#include <linux/jump_label.h>
#include <linux/kvm_para.h>
+#include <linux/reboot.h>
#include <linux/static_call.h>
#include <asm/paravirt.h>
struct static_key paravirt_steal_enabled;
struct static_key paravirt_steal_rq_enabled;
+static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64);
+static int has_steal_clock;
static u64 native_steal_clock(int cpu)
{
@@ -17,6 +20,57 @@ static u64 native_steal_clock(int cpu)
DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
+static bool steal_acc = true;
+static int __init parse_no_stealacc(char *arg)
+{
+ steal_acc = false;
+ return 0;
+}
+early_param("no-steal-acc", parse_no_stealacc);
+
+static u64 para_steal_clock(int cpu)
+{
+ u64 steal;
+ struct kvm_steal_time *src;
+ int version;
+
+ src = &per_cpu(steal_time, cpu);
+ do {
+
+ version = src->version;
+ /* Make sure that the version is read before the steal */
+ virt_rmb();
+ steal = src->steal;
+ /* Make sure that the steal is read before the next version */
+ virt_rmb();
+
+ } while ((version & 1) || (version != src->version));
+ return steal;
+}
+
+static int pv_enable_steal_time(void)
+{
+ int cpu = smp_processor_id();
+ struct kvm_steal_time *st;
+ unsigned long addr;
+
+ if (!has_steal_clock)
+ return -EPERM;
+
+ st = &per_cpu(steal_time, cpu);
+ addr = per_cpu_ptr_to_phys(st);
+
+ /* The whole structure kvm_steal_time should be one page */
+ if (PFN_DOWN(addr) != PFN_DOWN(addr + sizeof(*st))) {
+ pr_warn("Illegal PV steal time addr %lx\n", addr);
+ return -EFAULT;
+ }
+
+ addr |= KVM_STEAL_PHYS_VALID;
+ kvm_hypercall2(KVM_HCALL_FUNC_NOTIFY, KVM_FEATURE_STEAL_TIME, addr);
+ return 0;
+}
+
#ifdef CONFIG_SMP
static void pv_send_ipi_single(int cpu, unsigned int action)
{
@@ -112,6 +166,32 @@ static void pv_init_ipi(void)
if (r < 0)
panic("SWI0 IRQ request failed\n");
}
+
+static void pv_disable_steal_time(void)
+{
+ if (has_steal_clock)
+ kvm_hypercall2(KVM_HCALL_FUNC_NOTIFY, KVM_FEATURE_STEAL_TIME, 0);
+}
+
+static int pv_time_cpu_online(unsigned int cpu)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ pv_enable_steal_time();
+ local_irq_restore(flags);
+ return 0;
+}
+
+static int pv_time_cpu_down_prepare(unsigned int cpu)
+{
+ unsigned long flags;
+
+ local_irq_save(flags);
+ pv_disable_steal_time();
+ local_irq_restore(flags);
+ return 0;
+}
#endif
static bool kvm_para_available(void)
@@ -149,3 +229,56 @@ int __init pv_ipi_init(void)
return 0;
}
+
+static void pv_cpu_reboot(void *unused)
+{
+ pv_disable_steal_time();
+}
+
+static int pv_reboot_notify(struct notifier_block *nb, unsigned long code,
+ void *unused)
+{
+ on_each_cpu(pv_cpu_reboot, NULL, 1);
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block pv_reboot_nb = {
+ .notifier_call = pv_reboot_notify,
+};
+
+int __init pv_time_init(void)
+{
+ int feature;
+
+ if (!cpu_has_hypervisor)
+ return 0;
+ if (!kvm_para_available())
+ return 0;
+
+ feature = read_cpucfg(CPUCFG_KVM_FEATURE);
+ if (!(feature & KVM_FEATURE_STEAL_TIME))
+ return 0;
+
+ has_steal_clock = 1;
+ if (pv_enable_steal_time()) {
+ has_steal_clock = 0;
+ return 0;
+ }
+
+ register_reboot_notifier(&pv_reboot_nb);
+ static_call_update(pv_steal_clock, para_steal_clock);
+ static_key_slow_inc(¶virt_steal_enabled);
+#ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING
+ if (steal_acc)
+ static_key_slow_inc(¶virt_steal_rq_enabled);
+#endif
+
+#ifdef CONFIG_SMP
+ if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
+ "loongarch/pvi_time:online",
+ pv_time_cpu_online, pv_time_cpu_down_prepare) < 0)
+ pr_err("Failed to install cpu hotplug callbacks\n");
+#endif
+ pr_info("Using stolen time PV\n");
+ return 0;
+}
@@ -15,6 +15,7 @@
#include <asm/cpu-features.h>
#include <asm/loongarch.h>
+#include <asm/paravirt.h>
#include <asm/time.h>
u64 cpu_clock_freq;
@@ -214,4 +215,5 @@ void __init time_init(void)
constant_clockevent_init();
constant_clocksource_init();
+ pv_time_init();
}
Percpu struct kvm_steal_time is added here, its size is 64 bytes and also defined as 64 bytes, so that the whole structure is in one physical page. When vcpu is onlined, function pv_enable_steal_time() is called. This function will pass guest physical address of struct kvm_steal_time and tells hypervisor to enable steal time. When vcpu is offline, physical address is set as 0 and tells hypervisor to disable steal time. Here is output of vmstat on guest when there is workload on both host and guest. It shows steal time stat information. procs -----------memory---------- -----io---- -system-- ------cpu----- r b swpd free inact active bi bo in cs us sy id wa st 15 1 0 7583616 184112 72208 20 0 162 52 31 6 43 0 20 17 0 0 7583616 184704 72192 0 0 6318 6885 5 60 8 5 22 16 0 0 7583616 185392 72144 0 0 1766 1081 0 49 0 1 50 16 0 0 7583616 184816 72304 0 0 6300 6166 4 62 12 2 20 18 0 0 7583632 184480 72240 0 0 2814 1754 2 58 4 1 35 Signed-off-by: Bibo Mao <maobibo@loongson.cn> --- .../admin-guide/kernel-parameters.txt | 2 +- arch/loongarch/Kconfig | 11 ++ arch/loongarch/include/asm/paravirt.h | 5 + arch/loongarch/kernel/paravirt.c | 133 ++++++++++++++++++ arch/loongarch/kernel/time.c | 2 + 5 files changed, 152 insertions(+), 1 deletion(-)