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: Steven Price <[email protected]>
---
arch/arm64/kernel/Makefile | 1 +
arch/arm64/kernel/kvm.c | 155 +++++++++++++++++++++++++++++++++++++
include/linux/cpuhotplug.h | 1 +
3 files changed, 157 insertions(+)
create mode 100644 arch/arm64/kernel/kvm.c
diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
index 478491f07b4f..eb36edf9b930 100644
--- a/arch/arm64/kernel/Makefile
+++ b/arch/arm64/kernel/Makefile
@@ -63,6 +63,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o
obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o
obj-$(CONFIG_ARM64_SSBD) += ssbd.o
obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o
+obj-$(CONFIG_PARAVIRT) += kvm.o
obj-y += vdso/ probes/
obj-$(CONFIG_COMPAT_VDSO) += vdso32/
diff --git a/arch/arm64/kernel/kvm.c b/arch/arm64/kernel/kvm.c
new file mode 100644
index 000000000000..245398c79dae
--- /dev/null
+++ b/arch/arm64/kernel/kvm.c
@@ -0,0 +1,155 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2019 Arm Ltd.
+
+#define pr_fmt(fmt) "kvmarm-pv: " fmt
+
+#include <linux/arm-smccc.h>
+#include <linux/cpuhotplug.h>
+#include <linux/io.h>
+#include <linux/printk.h>
+#include <linux/psci.h>
+#include <linux/reboot.h>
+#include <linux/slab.h>
+
+#include <asm/paravirt.h>
+#include <asm/pvclock-abi.h>
+#include <asm/smp_plat.h>
+
+struct kvmarm_stolen_time_region {
+ struct pvclock_vcpu_stolen_time_info *kaddr;
+};
+
+static DEFINE_PER_CPU(struct kvmarm_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 kvm_steal_clock(int cpu)
+{
+ struct kvmarm_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 disable_stolen_time_current_cpu(void)
+{
+ struct kvmarm_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 stolen_time_dying_cpu(unsigned int cpu)
+{
+ return disable_stolen_time_current_cpu();
+}
+
+static int init_stolen_time_cpu(unsigned int cpu)
+{
+ struct kvmarm_stolen_time_region *reg;
+ struct arm_smccc_res res;
+
+ reg = this_cpu_ptr(&stolen_time_region);
+
+ if (reg->kaddr)
+ return 0;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
+
+ if ((long)res.a0 < 0)
+ return -EINVAL;
+
+ reg->kaddr = memremap(res.a0,
+ sizeof(struct pvclock_vcpu_stolen_time_info),
+ MEMREMAP_WB);
+
+ if (reg->kaddr == NULL) {
+ pr_warn("Failed to map stolen time data structure\n");
+ return -EINVAL;
+ }
+
+ if (le32_to_cpu(reg->kaddr->revision) != 0 ||
+ le32_to_cpu(reg->kaddr->attributes) != 0) {
+ pr_warn("Unexpected revision or attributes in stolen time data\n");
+ return -ENXIO;
+ }
+
+ return 0;
+}
+
+static int kvm_arm_init_stolen_time(void)
+{
+ int ret;
+
+ ret = cpuhp_setup_state(CPUHP_AP_ARM_KVMPV_STARTING,
+ "hypervisor/kvmarm/pv:starting",
+ init_stolen_time_cpu, stolen_time_dying_cpu);
+ if (ret < 0)
+ return ret;
+ return 0;
+}
+
+static bool has_kvm_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_FEATURES, &res);
+
+ if (res.a0 != SMCCC_RET_SUCCESS)
+ return false;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_FEATURES,
+ ARM_SMCCC_HV_PV_TIME_ST, &res);
+
+ if (res.a0 != SMCCC_RET_SUCCESS)
+ return false;
+
+ return true;
+}
+
+static int __init kvm_guest_init(void)
+{
+ int ret = 0;
+
+ if (!has_kvm_steal_clock())
+ return 0;
+
+ ret = kvm_arm_init_stolen_time();
+ if (ret)
+ return ret;
+
+ pv_ops.time.steal_clock = kvm_steal_clock;
+
+ static_key_slow_inc(¶virt_steal_enabled);
+ if (steal_acc)
+ static_key_slow_inc(¶virt_steal_rq_enabled);
+
+ pr_info("using stolen time PV\n");
+
+ return 0;
+}
+early_initcall(kvm_guest_init);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 068793a619ca..89d75edb5750 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -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,
--
2.20.1
On Fri, 2 Aug 2019 15:50:17 +0100
Steven Price <[email protected]> wrote:
> 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: Steven Price <[email protected]>
> ---
> arch/arm64/kernel/Makefile | 1 +
> arch/arm64/kernel/kvm.c | 155 +++++++++++++++++++++++++++++++++++++
nit: Why not using paravirt.c, which clearly states what it does? The
alternative would be to name it kvm-pv.c.
> include/linux/cpuhotplug.h | 1 +
> 3 files changed, 157 insertions(+)
> create mode 100644 arch/arm64/kernel/kvm.c
>
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index 478491f07b4f..eb36edf9b930 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -63,6 +63,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o
> obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o
> obj-$(CONFIG_ARM64_SSBD) += ssbd.o
> obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o
> +obj-$(CONFIG_PARAVIRT) += kvm.o
>
> obj-y += vdso/ probes/
> obj-$(CONFIG_COMPAT_VDSO) += vdso32/
> diff --git a/arch/arm64/kernel/kvm.c b/arch/arm64/kernel/kvm.c
> new file mode 100644
> index 000000000000..245398c79dae
> --- /dev/null
> +++ b/arch/arm64/kernel/kvm.c
> @@ -0,0 +1,155 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (C) 2019 Arm Ltd.
> +
> +#define pr_fmt(fmt) "kvmarm-pv: " fmt
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/cpuhotplug.h>
> +#include <linux/io.h>
> +#include <linux/printk.h>
> +#include <linux/psci.h>
> +#include <linux/reboot.h>
> +#include <linux/slab.h>
> +
> +#include <asm/paravirt.h>
> +#include <asm/pvclock-abi.h>
> +#include <asm/smp_plat.h>
> +
> +struct kvmarm_stolen_time_region {
> + struct pvclock_vcpu_stolen_time_info *kaddr;
> +};
> +
> +static DEFINE_PER_CPU(struct kvmarm_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 kvm_steal_clock(int cpu)
> +{
> + struct kvmarm_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 disable_stolen_time_current_cpu(void)
> +{
> + struct kvmarm_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 stolen_time_dying_cpu(unsigned int cpu)
> +{
> + return disable_stolen_time_current_cpu();
> +}
> +
> +static int init_stolen_time_cpu(unsigned int cpu)
> +{
> + struct kvmarm_stolen_time_region *reg;
> + struct arm_smccc_res res;
> +
> + reg = this_cpu_ptr(&stolen_time_region);
> +
> + if (reg->kaddr)
> + return 0;
Can this actually happen? It'd take two CPU_UP calls from the HP
notifiers to get in that situation...
> +
> + arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
> +
> + if ((long)res.a0 < 0)
> + return -EINVAL;
> +
> + reg->kaddr = memremap(res.a0,
> + sizeof(struct pvclock_vcpu_stolen_time_info),
> + MEMREMAP_WB);
> +
> + if (reg->kaddr == NULL) {
> + pr_warn("Failed to map stolen time data structure\n");
> + return -EINVAL;
-ENOMEM is the expected return code.
> + }
> +
> + if (le32_to_cpu(reg->kaddr->revision) != 0 ||
> + le32_to_cpu(reg->kaddr->attributes) != 0) {
> + pr_warn("Unexpected revision or attributes in stolen time data\n");
> + return -ENXIO;
> + }
> +
> + return 0;
> +}
> +
> +static int kvm_arm_init_stolen_time(void)
> +{
> + int ret;
> +
> + ret = cpuhp_setup_state(CPUHP_AP_ARM_KVMPV_STARTING,
> + "hypervisor/kvmarm/pv:starting",
> + init_stolen_time_cpu, stolen_time_dying_cpu);
> + if (ret < 0)
> + return ret;
> + return 0;
> +}
> +
> +static bool has_kvm_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_FEATURES, &res);
> +
> + if (res.a0 != SMCCC_RET_SUCCESS)
> + return false;
> +
> + arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_FEATURES,
> + ARM_SMCCC_HV_PV_TIME_ST, &res);
> +
> + if (res.a0 != SMCCC_RET_SUCCESS)
> + return false;
> +
> + return true;
> +}
> +
> +static int __init kvm_guest_init(void)
> +{
> + int ret = 0;
> +
> + if (!has_kvm_steal_clock())
> + return 0;
> +
> + ret = kvm_arm_init_stolen_time();
> + if (ret)
> + return ret;
> +
> + pv_ops.time.steal_clock = kvm_steal_clock;
> +
> + static_key_slow_inc(¶virt_steal_enabled);
> + if (steal_acc)
> + static_key_slow_inc(¶virt_steal_rq_enabled);
> +
> + pr_info("using stolen time PV\n");
> +
> + return 0;
> +}
> +early_initcall(kvm_guest_init);
Is there any reason why we wouldn't directly call into this rather than
using an initcall?
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 068793a619ca..89d75edb5750 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -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,
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
On 08/08/2019 16:29, Steven Price wrote:
> On 04/08/2019 10:53, Marc Zyngier wrote:
>> On Fri, 2 Aug 2019 15:50:17 +0100
>> Steven Price <[email protected]> wrote:
>>
>>> 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: Steven Price <[email protected]>
>>> ---
>>> arch/arm64/kernel/Makefile | 1 +
>>> arch/arm64/kernel/kvm.c | 155 +++++++++++++++++++++++++++++++++++++
[...]
>>> +static int __init kvm_guest_init(void)
>>> +{
>>> + int ret = 0;
>>> +
>>> + if (!has_kvm_steal_clock())
>>> + return 0;
>>> +
>>> + ret = kvm_arm_init_stolen_time();
>>> + if (ret)
>>> + return ret;
>>> +
>>> + pv_ops.time.steal_clock = kvm_steal_clock;
>>> +
>>> + static_key_slow_inc(¶virt_steal_enabled);
>>> + if (steal_acc)
>>> + static_key_slow_inc(¶virt_steal_rq_enabled);
>>> +
>>> + pr_info("using stolen time PV\n");
>>> +
>>> + return 0;
>>> +}
>>> +early_initcall(kvm_guest_init);
>>
>> Is there any reason why we wouldn't directly call into this rather than
>> using an initcall?
>
> I'm not sure where the direct call would go - any pointers?
I'd be temped to say arch/arm64/kernel/time.c:time_init(), provided that
there is no issue with the CPU hotplug lock (I remember hitting that a
while ago).
M.
--
Jazz is not dead, it just smells funny...
On 04/08/2019 10:53, Marc Zyngier wrote:
> On Fri, 2 Aug 2019 15:50:17 +0100
> Steven Price <[email protected]> wrote:
>
>> 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: Steven Price <[email protected]>
>> ---
>> arch/arm64/kernel/Makefile | 1 +
>> arch/arm64/kernel/kvm.c | 155 +++++++++++++++++++++++++++++++++++++
>
> nit: Why not using paravirt.c, which clearly states what it does? The
> alternative would be to name it kvm-pv.c.
I can move it to paravirt.c - seems reasonable.
>> include/linux/cpuhotplug.h | 1 +
>> 3 files changed, 157 insertions(+)
>> create mode 100644 arch/arm64/kernel/kvm.c
>>
>> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
>> index 478491f07b4f..eb36edf9b930 100644
>> --- a/arch/arm64/kernel/Makefile
>> +++ b/arch/arm64/kernel/Makefile
>> @@ -63,6 +63,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o
>> obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o
>> obj-$(CONFIG_ARM64_SSBD) += ssbd.o
>> obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o
>> +obj-$(CONFIG_PARAVIRT) += kvm.o
>>
>> obj-y += vdso/ probes/
>> obj-$(CONFIG_COMPAT_VDSO) += vdso32/
>> diff --git a/arch/arm64/kernel/kvm.c b/arch/arm64/kernel/kvm.c
>> new file mode 100644
>> index 000000000000..245398c79dae
>> --- /dev/null
>> +++ b/arch/arm64/kernel/kvm.c
>> @@ -0,0 +1,155 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +// Copyright (C) 2019 Arm Ltd.
>> +
>> +#define pr_fmt(fmt) "kvmarm-pv: " fmt
>> +
>> +#include <linux/arm-smccc.h>
>> +#include <linux/cpuhotplug.h>
>> +#include <linux/io.h>
>> +#include <linux/printk.h>
>> +#include <linux/psci.h>
>> +#include <linux/reboot.h>
>> +#include <linux/slab.h>
>> +
>> +#include <asm/paravirt.h>
>> +#include <asm/pvclock-abi.h>
>> +#include <asm/smp_plat.h>
>> +
>> +struct kvmarm_stolen_time_region {
>> + struct pvclock_vcpu_stolen_time_info *kaddr;
>> +};
>> +
>> +static DEFINE_PER_CPU(struct kvmarm_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 kvm_steal_clock(int cpu)
>> +{
>> + struct kvmarm_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 disable_stolen_time_current_cpu(void)
>> +{
>> + struct kvmarm_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 stolen_time_dying_cpu(unsigned int cpu)
>> +{
>> + return disable_stolen_time_current_cpu();
>> +}
>> +
>> +static int init_stolen_time_cpu(unsigned int cpu)
>> +{
>> + struct kvmarm_stolen_time_region *reg;
>> + struct arm_smccc_res res;
>> +
>> + reg = this_cpu_ptr(&stolen_time_region);
>> +
>> + if (reg->kaddr)
>> + return 0;
>
> Can this actually happen? It'd take two CPU_UP calls from the HP
> notifiers to get in that situation...
Yes, something would have to be very broken for that to happen - I'll
remove this check.
>> +
>> + arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
>> +
>> + if ((long)res.a0 < 0)
>> + return -EINVAL;
>> +
>> + reg->kaddr = memremap(res.a0,
>> + sizeof(struct pvclock_vcpu_stolen_time_info),
>> + MEMREMAP_WB);
>> +
>> + if (reg->kaddr == NULL) {
>> + pr_warn("Failed to map stolen time data structure\n");
>> + return -EINVAL;
>
> -ENOMEM is the expected return code.
Ok
>> + }
>> +
>> + if (le32_to_cpu(reg->kaddr->revision) != 0 ||
>> + le32_to_cpu(reg->kaddr->attributes) != 0) {
>> + pr_warn("Unexpected revision or attributes in stolen time data\n");
>> + return -ENXIO;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static int kvm_arm_init_stolen_time(void)
>> +{
>> + int ret;
>> +
>> + ret = cpuhp_setup_state(CPUHP_AP_ARM_KVMPV_STARTING,
>> + "hypervisor/kvmarm/pv:starting",
>> + init_stolen_time_cpu, stolen_time_dying_cpu);
>> + if (ret < 0)
>> + return ret;
>> + return 0;
>> +}
>> +
>> +static bool has_kvm_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_FEATURES, &res);
>> +
>> + if (res.a0 != SMCCC_RET_SUCCESS)
>> + return false;
>> +
>> + arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_FEATURES,
>> + ARM_SMCCC_HV_PV_TIME_ST, &res);
>> +
>> + if (res.a0 != SMCCC_RET_SUCCESS)
>> + return false;
>> +
>> + return true;
>> +}
>> +
>> +static int __init kvm_guest_init(void)
>> +{
>> + int ret = 0;
>> +
>> + if (!has_kvm_steal_clock())
>> + return 0;
>> +
>> + ret = kvm_arm_init_stolen_time();
>> + if (ret)
>> + return ret;
>> +
>> + pv_ops.time.steal_clock = kvm_steal_clock;
>> +
>> + static_key_slow_inc(¶virt_steal_enabled);
>> + if (steal_acc)
>> + static_key_slow_inc(¶virt_steal_rq_enabled);
>> +
>> + pr_info("using stolen time PV\n");
>> +
>> + return 0;
>> +}
>> +early_initcall(kvm_guest_init);
>
> Is there any reason why we wouldn't directly call into this rather than
> using an initcall?
I'm not sure where the direct call would go - any pointers?
Thanks,
Steve
>> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
>> index 068793a619ca..89d75edb5750 100644
>> --- a/include/linux/cpuhotplug.h
>> +++ b/include/linux/cpuhotplug.h
>> @@ -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,
>
>
> Thanks,
>
> M.
>
On 2019/8/2 22:50, Steven Price wrote:
> 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: Steven Price <[email protected]>
> ---
> arch/arm64/kernel/Makefile | 1 +
> arch/arm64/kernel/kvm.c | 155 +++++++++++++++++++++++++++++++++++++
> include/linux/cpuhotplug.h | 1 +
> 3 files changed, 157 insertions(+)
> create mode 100644 arch/arm64/kernel/kvm.c
>
> diff --git a/arch/arm64/kernel/Makefile b/arch/arm64/kernel/Makefile
> index 478491f07b4f..eb36edf9b930 100644
> --- a/arch/arm64/kernel/Makefile
> +++ b/arch/arm64/kernel/Makefile
> @@ -63,6 +63,7 @@ obj-$(CONFIG_CRASH_CORE) += crash_core.o
> obj-$(CONFIG_ARM_SDE_INTERFACE) += sdei.o
> obj-$(CONFIG_ARM64_SSBD) += ssbd.o
> obj-$(CONFIG_ARM64_PTR_AUTH) += pointer_auth.o
> +obj-$(CONFIG_PARAVIRT) += kvm.o
>
> obj-y += vdso/ probes/
> obj-$(CONFIG_COMPAT_VDSO) += vdso32/
> diff --git a/arch/arm64/kernel/kvm.c b/arch/arm64/kernel/kvm.c
> new file mode 100644
> index 000000000000..245398c79dae
> --- /dev/null
> +++ b/arch/arm64/kernel/kvm.c
> @@ -0,0 +1,155 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (C) 2019 Arm Ltd.
> +
> +#define pr_fmt(fmt) "kvmarm-pv: " fmt
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/cpuhotplug.h>
> +#include <linux/io.h>
> +#include <linux/printk.h>
> +#include <linux/psci.h>
> +#include <linux/reboot.h>
> +#include <linux/slab.h>
> +
> +#include <asm/paravirt.h>
> +#include <asm/pvclock-abi.h>
> +#include <asm/smp_plat.h>
> +
> +struct kvmarm_stolen_time_region {
> + struct pvclock_vcpu_stolen_time_info *kaddr;
> +};
> +
> +static DEFINE_PER_CPU(struct kvmarm_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 kvm_steal_clock(int cpu)
> +{
> + struct kvmarm_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 disable_stolen_time_current_cpu(void)
> +{
> + struct kvmarm_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 stolen_time_dying_cpu(unsigned int cpu)
> +{
> + return disable_stolen_time_current_cpu();
> +}
> +
> +static int init_stolen_time_cpu(unsigned int cpu)
> +{
> + struct kvmarm_stolen_time_region *reg;
> + struct arm_smccc_res res;
> +
> + reg = this_cpu_ptr(&stolen_time_region);
> +
> + if (reg->kaddr)
> + return 0;
> +
> + arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_TIME_ST, &res);
> +
> + if ((long)res.a0 < 0)
> + return -EINVAL;
Hi Steven,
Since userspace is not involved yet (right?), no one will create the
PV_TIME device for guest (and no one will specify the IPA of the shared
stolen time region), and I guess we will get a "not supported" error
here.
So what should we do if we want to test this series now? Any userspace
tools? If no, do you have any plans for userspace developing? ;-)
Thanks,
zenghui
> +
> + reg->kaddr = memremap(res.a0,
> + sizeof(struct pvclock_vcpu_stolen_time_info),
> + MEMREMAP_WB);
> +
> + if (reg->kaddr == NULL) {
> + pr_warn("Failed to map stolen time data structure\n");
> + return -EINVAL;
> + }
> +
> + if (le32_to_cpu(reg->kaddr->revision) != 0 ||
> + le32_to_cpu(reg->kaddr->attributes) != 0) {
> + pr_warn("Unexpected revision or attributes in stolen time data\n");
> + return -ENXIO;
> + }
> +
> + return 0;
> +}
> +
> +static int kvm_arm_init_stolen_time(void)
> +{
> + int ret;
> +
> + ret = cpuhp_setup_state(CPUHP_AP_ARM_KVMPV_STARTING,
> + "hypervisor/kvmarm/pv:starting",
> + init_stolen_time_cpu, stolen_time_dying_cpu);
> + if (ret < 0)
> + return ret;
> + return 0;
> +}
> +
> +static bool has_kvm_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_FEATURES, &res);
> +
> + if (res.a0 != SMCCC_RET_SUCCESS)
> + return false;
> +
> + arm_smccc_1_1_invoke(ARM_SMCCC_HV_PV_FEATURES,
> + ARM_SMCCC_HV_PV_TIME_ST, &res);
> +
> + if (res.a0 != SMCCC_RET_SUCCESS)
> + return false;
> +
> + return true;
> +}
> +
> +static int __init kvm_guest_init(void)
> +{
> + int ret = 0;
> +
> + if (!has_kvm_steal_clock())
> + return 0;
> +
> + ret = kvm_arm_init_stolen_time();
> + if (ret)
> + return ret;
> +
> + pv_ops.time.steal_clock = kvm_steal_clock;
> +
> + static_key_slow_inc(¶virt_steal_enabled);
> + if (steal_acc)
> + static_key_slow_inc(¶virt_steal_rq_enabled);
> +
> + pr_info("using stolen time PV\n");
> +
> + return 0;
> +}
> +early_initcall(kvm_guest_init);
> diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
> index 068793a619ca..89d75edb5750 100644
> --- a/include/linux/cpuhotplug.h
> +++ b/include/linux/cpuhotplug.h
> @@ -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,
>
On 09/08/2019 14:51, Zenghui Yu wrote:
[...]
> Hi Steven,
>
> Since userspace is not involved yet (right?), no one will create the
> PV_TIME device for guest (and no one will specify the IPA of the shared
> stolen time region), and I guess we will get a "not supported" error
> here.
>
> So what should we do if we want to test this series now? Any userspace
> tools? If no, do you have any plans for userspace developing? ;-)
At the moment I have the following patch to kvmtool which creates the
PV_TIME device - this isn't in a state to go upstream, and Marc has
asked that I rework the memory allocation, so this will need to change.
It's a little ugly as it simply reserves the first page of RAM to use
for the PV time structures.
----8<----
diff --git a/Makefile b/Makefile
index 3862112..a79956b 100644
--- a/Makefile
+++ b/Makefile
@@ -158,7 +158,7 @@ endif
# ARM
OBJS_ARM_COMMON := arm/fdt.o arm/gic.o arm/gicv2m.o arm/ioport.o \
arm/kvm.o arm/kvm-cpu.o arm/pci.o arm/timer.o \
- arm/pmu.o
+ arm/pmu.o arm/pvtime.o
HDRS_ARM_COMMON := arm/include
ifeq ($(ARCH), arm)
DEFINES += -DCONFIG_ARM
diff --git a/arm/fdt.c b/arm/fdt.c
index c80e6da..19eccbc 100644
--- a/arm/fdt.c
+++ b/arm/fdt.c
@@ -119,6 +119,7 @@ static int setup_fdt(struct kvm *kvm)
/* Create new tree without a reserve map */
_FDT(fdt_create(fdt, FDT_MAX_SIZE));
+ _FDT(fdt_add_reservemap_entry(fdt, kvm->arch.memory_guest_start, 4096));
_FDT(fdt_finish_reservemap(fdt));
/* Header */
diff --git a/arm/kvm.c b/arm/kvm.c
index 1f85fc6..8bbfef1 100644
--- a/arm/kvm.c
+++ b/arm/kvm.c
@@ -11,6 +11,8 @@
#include <linux/kvm.h>
#include <linux/sizes.h>
+int pvtime_create(struct kvm *kvm);
+
struct kvm_ext kvm_req_ext[] = {
{ DEFINE_KVM_EXT(KVM_CAP_IRQCHIP) },
{ DEFINE_KVM_EXT(KVM_CAP_ONE_REG) },
@@ -86,6 +88,10 @@ void kvm__arch_init(struct kvm *kvm, const char *hugetlbfs_path, u64 ram_size)
/* Create the virtual GIC. */
if (gic__create(kvm, kvm->cfg.arch.irqchip))
die("Failed to create virtual GIC");
+
+ /* Setup PV time */
+ if (pvtime_create(kvm))
+ die("Failed to initialise PV time");
}
#define FDT_ALIGN SZ_2M
diff --git a/arm/pvtime.c b/arm/pvtime.c
new file mode 100644
index 0000000..abcaab3
--- /dev/null
+++ b/arm/pvtime.c
@@ -0,0 +1,77 @@
+#include "kvm/kvm.h"
+
+#define KVM_DEV_TYPE_ARM_PV_TIME (KVM_DEV_TYPE_ARM_VGIC_ITS+2)
+
+/* Device Control API: PV_TIME */
+#define KVM_DEV_ARM_PV_TIME_PADDR 0
+#define KVM_DEV_ARM_PV_TIME_FREQUENCY 3
+
+#define KVM_DEV_ARM_PV_TIME_ST 0
+#define KVM_DEV_ARM_PV_TIME_LPT 1
+
+static int pvtime_fd;
+
+int pvtime_create(struct kvm *kvm);
+
+int pvtime_create(struct kvm *kvm)
+{
+ int err;
+ u64 lpt_paddr = 0x10000000;
+ u64 st_paddr = lpt_paddr + 4096;
+ u32 frequency = 100 * 1000 * 1000;
+
+ printf("lpt_paddr=%llx\n", lpt_paddr);
+
+ struct kvm_create_device pvtime_device = {
+ .type = KVM_DEV_TYPE_ARM_PV_TIME,
+ .flags = 0,
+ };
+
+ err = ioctl(kvm->vm_fd, KVM_CREATE_DEVICE, &pvtime_device);
+ if (err) {
+ printf("Failed to create PV device\n");
+ return 0;
+ }
+
+ pvtime_fd = pvtime_device.fd;
+
+ struct kvm_device_attr lpt_base = {
+ .group = KVM_DEV_ARM_PV_TIME_PADDR,
+ .attr = KVM_DEV_ARM_PV_TIME_LPT,
+ .addr = (u64)(unsigned long)&lpt_paddr
+ };
+ struct kvm_device_attr st_base = {
+ .group = KVM_DEV_ARM_PV_TIME_PADDR,
+ .attr = KVM_DEV_ARM_PV_TIME_ST,
+ .addr = (u64)(unsigned long)&st_paddr
+ };
+
+ struct kvm_device_attr lpt_freq = {
+ .group = KVM_DEV_ARM_PV_TIME_FREQUENCY,
+ .attr = KVM_DEV_ARM_PV_TIME_LPT,
+ .addr = (u64)(unsigned long)&frequency
+ };
+
+ err = ioctl(pvtime_fd, KVM_SET_DEVICE_ATTR, &lpt_base);
+ if (err) {
+ perror("ioctl lpt_base failed");
+ printf("Ignoring LPT...\n");
+ }
+ err = ioctl(pvtime_fd, KVM_SET_DEVICE_ATTR, &st_base);
+ if (err) {
+ perror("ioctl st_base failed");
+ goto out_err;
+ }
+ err = ioctl(pvtime_fd, KVM_SET_DEVICE_ATTR, &lpt_freq);
+ if (err) {
+ perror("ioctl lpt_freq failed");
+ printf("Ignoring LPT...\n");
+ }
+
+ printf("PV time setup\n");
+
+ return 0;
+out_err:
+ close(pvtime_fd);
+ return err;
+}
On 2019/8/12 18:39, Steven Price wrote:
> On 09/08/2019 14:51, Zenghui Yu wrote:
> [...]
>> Hi Steven,
>>
>> Since userspace is not involved yet (right?), no one will create the
>> PV_TIME device for guest (and no one will specify the IPA of the shared
>> stolen time region), and I guess we will get a "not supported" error
>> here.
>>
>> So what should we do if we want to test this series now? Any userspace
>> tools? If no, do you have any plans for userspace developing? ;-)
>
> At the moment I have the following patch to kvmtool which creates the
> PV_TIME device - this isn't in a state to go upstream, and Marc has
> asked that I rework the memory allocation, so this will need to change.
>
> It's a little ugly as it simply reserves the first page of RAM to use
> for the PV time structures.
Thanks for sharing the code. It's good enough to show what is required
in user-space.
(I'm not familiar with kvmtool. I will first take some time to move the
steal time part to Qemu and see what will happen.)
Thanks,
zenghui
> ----8<----
> diff --git a/Makefile b/Makefile
> index 3862112..a79956b 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -158,7 +158,7 @@ endif
> # ARM
> OBJS_ARM_COMMON := arm/fdt.o arm/gic.o arm/gicv2m.o arm/ioport.o \
> arm/kvm.o arm/kvm-cpu.o arm/pci.o arm/timer.o \
> - arm/pmu.o
> + arm/pmu.o arm/pvtime.o
> HDRS_ARM_COMMON := arm/include
> ifeq ($(ARCH), arm)
> DEFINES += -DCONFIG_ARM
> diff --git a/arm/fdt.c b/arm/fdt.c
> index c80e6da..19eccbc 100644
> --- a/arm/fdt.c
> +++ b/arm/fdt.c
> @@ -119,6 +119,7 @@ static int setup_fdt(struct kvm *kvm)
>
> /* Create new tree without a reserve map */
> _FDT(fdt_create(fdt, FDT_MAX_SIZE));
> + _FDT(fdt_add_reservemap_entry(fdt, kvm->arch.memory_guest_start, 4096));
> _FDT(fdt_finish_reservemap(fdt));
>
> /* Header */
> diff --git a/arm/kvm.c b/arm/kvm.c
> index 1f85fc6..8bbfef1 100644
> --- a/arm/kvm.c
> +++ b/arm/kvm.c
> @@ -11,6 +11,8 @@
> #include <linux/kvm.h>
> #include <linux/sizes.h>
>
> +int pvtime_create(struct kvm *kvm);
> +
> struct kvm_ext kvm_req_ext[] = {
> { DEFINE_KVM_EXT(KVM_CAP_IRQCHIP) },
> { DEFINE_KVM_EXT(KVM_CAP_ONE_REG) },
> @@ -86,6 +88,10 @@ void kvm__arch_init(struct kvm *kvm, const char *hugetlbfs_path, u64 ram_size)
> /* Create the virtual GIC. */
> if (gic__create(kvm, kvm->cfg.arch.irqchip))
> die("Failed to create virtual GIC");
> +
> + /* Setup PV time */
> + if (pvtime_create(kvm))
> + die("Failed to initialise PV time");
> }
>
> #define FDT_ALIGN SZ_2M
> diff --git a/arm/pvtime.c b/arm/pvtime.c
> new file mode 100644
> index 0000000..abcaab3
> --- /dev/null
> +++ b/arm/pvtime.c
> @@ -0,0 +1,77 @@
> +#include "kvm/kvm.h"
> +
> +#define KVM_DEV_TYPE_ARM_PV_TIME (KVM_DEV_TYPE_ARM_VGIC_ITS+2)
> +
> +/* Device Control API: PV_TIME */
> +#define KVM_DEV_ARM_PV_TIME_PADDR 0
> +#define KVM_DEV_ARM_PV_TIME_FREQUENCY 3
> +
> +#define KVM_DEV_ARM_PV_TIME_ST 0
> +#define KVM_DEV_ARM_PV_TIME_LPT 1
> +
> +static int pvtime_fd;
> +
> +int pvtime_create(struct kvm *kvm);
> +
> +int pvtime_create(struct kvm *kvm)
> +{
> + int err;
> + u64 lpt_paddr = 0x10000000;
> + u64 st_paddr = lpt_paddr + 4096;
> + u32 frequency = 100 * 1000 * 1000;
> +
> + printf("lpt_paddr=%llx\n", lpt_paddr);
> +
> + struct kvm_create_device pvtime_device = {
> + .type = KVM_DEV_TYPE_ARM_PV_TIME,
> + .flags = 0,
> + };
> +
> + err = ioctl(kvm->vm_fd, KVM_CREATE_DEVICE, &pvtime_device);
> + if (err) {
> + printf("Failed to create PV device\n");
> + return 0;
> + }
> +
> + pvtime_fd = pvtime_device.fd;
> +
> + struct kvm_device_attr lpt_base = {
> + .group = KVM_DEV_ARM_PV_TIME_PADDR,
> + .attr = KVM_DEV_ARM_PV_TIME_LPT,
> + .addr = (u64)(unsigned long)&lpt_paddr
> + };
> + struct kvm_device_attr st_base = {
> + .group = KVM_DEV_ARM_PV_TIME_PADDR,
> + .attr = KVM_DEV_ARM_PV_TIME_ST,
> + .addr = (u64)(unsigned long)&st_paddr
> + };
> +
> + struct kvm_device_attr lpt_freq = {
> + .group = KVM_DEV_ARM_PV_TIME_FREQUENCY,
> + .attr = KVM_DEV_ARM_PV_TIME_LPT,
> + .addr = (u64)(unsigned long)&frequency
> + };
> +
> + err = ioctl(pvtime_fd, KVM_SET_DEVICE_ATTR, &lpt_base);
> + if (err) {
> + perror("ioctl lpt_base failed");
> + printf("Ignoring LPT...\n");
> + }
> + err = ioctl(pvtime_fd, KVM_SET_DEVICE_ATTR, &st_base);
> + if (err) {
> + perror("ioctl st_base failed");
> + goto out_err;
> + }
> + err = ioctl(pvtime_fd, KVM_SET_DEVICE_ATTR, &lpt_freq);
> + if (err) {
> + perror("ioctl lpt_freq failed");
> + printf("Ignoring LPT...\n");
> + }
> +
> + printf("PV time setup\n");
> +
> + return 0;
> +out_err:
> + close(pvtime_fd);
> + return err;
> +}