Commit e0685fa2 authored by Steven Price's avatar Steven Price Committed by Marc Zyngier

arm64: Retrieve stolen time as paravirtualized guest

Enable paravirtualization features when running under a hypervisor
supporting the PV_TIME_ST hypercall.

For each (v)CPU, we ask the hypervisor for the location of a shared
page which the hypervisor will use to report stolen time to us. We set
pv_time_ops to the stolen time function which simply reads the stolen
value from the shared page for a VCPU. We guarantee single-copy
atomicity using READ_ONCE which means we can also read the stolen
time for another VCPU than the currently running one while it is
potentially being updated by the hypervisor.
Signed-off-by: default avatarSteven Price <steven.price@arm.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
parent ce4d5ca2
......@@ -3083,9 +3083,9 @@
[X86,PV_OPS] Disable paravirtualized VMware scheduler
clock and use the default one.
no-steal-acc [X86,KVM] Disable paravirtualized steal time accounting.
steal time is computed, but won't influence scheduler
behaviour
no-steal-acc [X86,KVM,ARM64] Disable paravirtualized steal time
accounting. steal time is computed, but won't
influence scheduler behaviour
nolapic [X86-32,APIC] Do not enable or use the local APIC.
......
......@@ -21,6 +21,13 @@ static inline u64 paravirt_steal_clock(int cpu)
{
return pv_ops.time.steal_clock(cpu);
}
#endif
int __init pv_time_init(void);
#else
#define pv_time_init() do {} while (0)
#endif // CONFIG_PARAVIRT
#endif
......@@ -6,13 +6,153 @@
* Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
*/
#define pr_fmt(fmt) "arm-pv: " fmt
#include <linux/arm-smccc.h>
#include <linux/cpuhotplug.h>
#include <linux/export.h>
#include <linux/io.h>
#include <linux/jump_label.h>
#include <linux/printk.h>
#include <linux/psci.h>
#include <linux/reboot.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <asm/paravirt.h>
#include <asm/pvclock-abi.h>
#include <asm/smp_plat.h>
struct static_key paravirt_steal_enabled;
struct static_key paravirt_steal_rq_enabled;
struct paravirt_patch_template pv_ops;
EXPORT_SYMBOL_GPL(pv_ops);
struct pv_time_stolen_time_region {
struct pvclock_vcpu_stolen_time *kaddr;
};
static DEFINE_PER_CPU(struct pv_time_stolen_time_region, stolen_time_region);
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);
/* return stolen time in ns by asking the hypervisor */
static u64 pv_steal_clock(int cpu)
{
struct pv_time_stolen_time_region *reg;
reg = per_cpu_ptr(&stolen_time_region, cpu);
if (!reg->kaddr) {
pr_warn_once("stolen time enabled but not configured for cpu %d\n",
cpu);
return 0;
}
return le64_to_cpu(READ_ONCE(reg->kaddr->stolen_time));
}
static int stolen_time_dying_cpu(unsigned int cpu)
{
struct pv_time_stolen_time_region *reg;
reg = this_cpu_ptr(&stolen_time_region);
if (!reg->kaddr)
return 0;
memunmap(reg->kaddr);
memset(reg, 0, sizeof(*reg));
return 0;
}
static int init_stolen_time_cpu(unsigned int cpu)
{
struct pv_time_stolen_time_region *reg;
struct arm_smccc_res res;
reg = this_cpu_ptr(&stolen_time_region);
arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
return -EINVAL;
reg->kaddr = memremap(res.a0,
sizeof(struct pvclock_vcpu_stolen_time),
MEMREMAP_WB);
if (!reg->kaddr) {
pr_warn("Failed to map stolen time data structure\n");
return -ENOMEM;
}
if (le32_to_cpu(reg->kaddr->revision) != 0 ||
le32_to_cpu(reg->kaddr->attributes) != 0) {
pr_warn_once("Unexpected revision or attributes in stolen time data\n");
return -ENXIO;
}
return 0;
}
static int pv_time_init_stolen_time(void)
{
int ret;
ret = cpuhp_setup_state(CPUHP_AP_ARM_KVMPV_STARTING,
"hypervisor/arm/pvtime:starting",
init_stolen_time_cpu, stolen_time_dying_cpu);
if (ret < 0)
return ret;
return 0;
}
static bool has_pv_steal_clock(void)
{
struct arm_smccc_res res;
/* To detect the presence of PV time support we require SMCCC 1.1+ */
if (psci_ops.smccc_version < SMCCC_VERSION_1_1)
return false;
arm_smccc_1_1_invoke(ARM_SMCCC_ARCH_FEATURES_FUNC_ID,
ARM_SMCCC_HV_PV_TIME_FEATURES, &res);
if (res.a0 != SMCCC_RET_SUCCESS)
return false;
arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_FEATURES,
ARM_SMCCC_HV_PV_TIME_ST, &res);
return (res.a0 == SMCCC_RET_SUCCESS);
}
int __init pv_time_init(void)
{
int ret;
if (!has_pv_steal_clock())
return 0;
ret = pv_time_init_stolen_time();
if (ret)
return ret;
pv_ops.time.steal_clock = pv_steal_clock;
static_key_slow_inc(&paravirt_steal_enabled);
if (steal_acc)
static_key_slow_inc(&paravirt_steal_rq_enabled);
pr_info("using stolen time PV\n");
return 0;
}
......@@ -30,6 +30,7 @@
#include <asm/thread_info.h>
#include <asm/stacktrace.h>
#include <asm/paravirt.h>
unsigned long profile_pc(struct pt_regs *regs)
{
......@@ -65,4 +66,6 @@ void __init time_init(void)
/* Calibrate the delay loop directly */
lpj_fine = arch_timer_rate / HZ;
pv_time_init();
}
......@@ -136,6 +136,7 @@ enum cpuhp_state {
/* Must be the last timer callback */
CPUHP_AP_DUMMY_TIMER_STARTING,
CPUHP_AP_ARM_XEN_STARTING,
CPUHP_AP_ARM_KVMPV_STARTING,
CPUHP_AP_ARM_CORESIGHT_STARTING,
CPUHP_AP_ARM64_ISNDEP_STARTING,
CPUHP_AP_SMPCFD_DYING,
......
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