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From: Zenghui Yu <yuzenghui@huawei.com>
To: Steven Price <steven.price@arm.com>
Cc: kvm@vger.kernel.org, linux-doc@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Russell King <linux@armlinux.org.uk>,
	linux-kernel@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Will Deacon <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 9/9] arm64: Retrieve stolen time as paravirtualized guest
Date: Fri, 9 Aug 2019 21:51:39 +0800
Message-ID: <5d763c8e-9c06-c448-2644-25bfa0e57e8c@huawei.com> (raw)
In-Reply-To: <20190802145017.42543-10-steven.price@arm.com>

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 <steven.price@arm.com>
> ---
>   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(&paravirt_steal_enabled);
> +	if (steal_acc)
> +		static_key_slow_inc(&paravirt_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,
> 

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  parent reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-02 14:50 [PATCH 0/9] arm64: Stolen time support Steven Price
2019-08-02 14:50 ` [PATCH 1/9] KVM: arm64: Document PV-time interface Steven Price
2019-08-03 11:13   ` Marc Zyngier
2019-08-05 13:06     ` Steven Price
2019-08-05  3:23   ` Zenghui Yu
2019-08-05 13:06     ` Steven Price
2019-08-05 16:40   ` Christophe de Dinechin
2019-08-07 13:21     ` Steven Price
2019-08-07 14:28       ` Christophe de Dinechin
2019-08-07 15:26         ` Steven Price
2019-08-02 14:50 ` [PATCH 2/9] KVM: arm/arm64: Factor out hypercall handling from PSCI code Steven Price
2019-08-02 14:50 ` [PATCH 3/9] KVM: arm64: Implement PV_FEATURES call Steven Price
2019-08-03 11:21   ` Marc Zyngier
2019-08-05 13:14     ` Steven Price
2019-08-02 14:50 ` [PATCH 4/9] KVM: arm64: Support stolen time reporting via shared structure Steven Price
2019-08-03 11:55   ` Marc Zyngier
2019-08-05 14:09     ` Steven Price
2019-08-03 17:58   ` Marc Zyngier
2019-08-03 18:13     ` Marc Zyngier
2019-08-05 14:18       ` Steven Price
2019-08-02 14:50 ` [PATCH 5/9] KVM: Allow kvm_device_ops to be const Steven Price
2019-08-02 14:50 ` [PATCH 6/9] KVM: arm64: Provide a PV_TIME device to user space Steven Price
2019-08-03 12:51   ` Marc Zyngier
2019-08-03 17:34     ` Marc Zyngier
2019-08-07 13:39       ` Steven Price
2019-08-07 13:51         ` Marc Zyngier
2019-08-05 16:10     ` Steven Price
2019-08-05 16:28       ` Marc Zyngier
2019-08-02 14:50 ` [PATCH 7/9] arm/arm64: Provide a wrapper for SMCCC 1.1 calls Steven Price
2019-08-05 10:03   ` Will Deacon
2019-08-02 14:50 ` [PATCH 8/9] arm/arm64: Make use of the SMCCC 1.1 wrapper Steven Price
2019-08-02 14:50 ` [PATCH 9/9] arm64: Retrieve stolen time as paravirtualized guest Steven Price
2019-08-04  9:53   ` Marc Zyngier
2019-08-08 15:29     ` Steven Price
2019-08-08 15:49       ` Marc Zyngier
2019-08-09 13:51   ` Zenghui Yu [this message]
2019-08-12 10:39     ` Steven Price
2019-08-13  6:06       ` Zenghui Yu
2019-08-03 18:05 ` [PATCH 0/9] arm64: Stolen time support Marc Zyngier
2019-08-05 13:06   ` Steven Price
2019-08-05 13:26     ` Marc Zyngier
2019-08-14 13:02     ` Alexander Graf
2019-08-14 14:19       ` Marc Zyngier
2019-08-14 14:52         ` [UNVERIFIED SENDER] " Alexander Graf
2019-08-16 10:23           ` Steven Price

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