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Wysocki" , Viresh Kumar , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Sudeep Holla , David Dai , Saravana Kannan Cc: Quentin Perret , Masami Hiramatsu , Will Deacon , Peter Zijlstra , Vincent Guittot , Marc Zyngier , Oliver Upton , Dietmar Eggemann , Pavan Kondeti , Gupta Pankaj , Mel Gorman , kernel-team@android.com, linux-pm@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Introduce a virtualized cpufreq driver for guest kernels to improve performance and power of workloads within VMs. This driver does two main things: 1. Sends the frequency of vCPUs as a hint to the host. The host uses the hint to schedule the vCPU threads and decide physical CPU frequency. 2. If a VM does not support a virtualized FIE(like AMUs), it queries the host CPU frequency by reading a MMIO region of a virtual cpufreq device to update the guest's frequency scaling factor periodically. This enables accurate Per-Entity Load Tracking for tasks running in the guest. Co-developed-by: Saravana Kannan Signed-off-by: Saravana Kannan Signed-off-by: David Dai --- drivers/cpufreq/Kconfig | 14 ++ drivers/cpufreq/Makefile | 1 + drivers/cpufreq/virtual-cpufreq.c | 333 ++++++++++++++++++++++++++++++ include/linux/arch_topology.h | 1 + 4 files changed, 349 insertions(+) create mode 100644 drivers/cpufreq/virtual-cpufreq.c diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig index 2561b215432a..92a83a9bb2e1 100644 --- a/drivers/cpufreq/Kconfig +++ b/drivers/cpufreq/Kconfig @@ -217,6 +217,20 @@ config CPUFREQ_DT If in doubt, say N. +config CPUFREQ_VIRT + tristate "Virtual cpufreq driver" + depends on GENERIC_ARCH_TOPOLOGY + help + This adds a virtualized cpufreq driver for guest kernels that + read/writes to a MMIO region for a virtualized cpufreq device to + communicate with the host. It sends performance requests to the host + which gets used as a hint to schedule vCPU threads and select CPU + frequency. If a VM does not support a virtualized FIE such as AMUs, + it updates the frequency scaling factor by polling host CPU frequency + to enable accurate Per-Entity Load Tracking for tasks running in the guest. + + If in doubt, say N. + config CPUFREQ_DT_PLATDEV tristate "Generic DT based cpufreq platdev driver" depends on OF diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile index 0f184031dd12..10d7d6e55da8 100644 --- a/drivers/cpufreq/Makefile +++ b/drivers/cpufreq/Makefile @@ -16,6 +16,7 @@ obj-$(CONFIG_CPU_FREQ_GOV_ATTR_SET) += cpufreq_governor_attr_set.o obj-$(CONFIG_CPUFREQ_DT) += cpufreq-dt.o obj-$(CONFIG_CPUFREQ_DT_PLATDEV) += cpufreq-dt-platdev.o +obj-$(CONFIG_CPUFREQ_VIRT) += virtual-cpufreq.o # Traces CFLAGS_amd-pstate-trace.o := -I$(src) diff --git a/drivers/cpufreq/virtual-cpufreq.c b/drivers/cpufreq/virtual-cpufreq.c new file mode 100644 index 000000000000..a050b3a6737f --- /dev/null +++ b/drivers/cpufreq/virtual-cpufreq.c @@ -0,0 +1,333 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2024 Google LLC + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* + * CPU0..CPUn + * +-------------+-------------------------------+--------+-------+ + * | Register | Description | Offset | Len | + * +-------------+-------------------------------+--------+-------+ + * | cur_perf | read this register to get | 0x0 | 0x4 | + * | | the current perf (integer val | | | + * | | representing perf relative to | | | + * | | max performance) | | | + * | | that vCPU is running at | | | + * +-------------+-------------------------------+--------+-------+ + * | set_perf | write to this register to set | 0x4 | 0x4 | + * | | perf value of the vCPU | | | + * +-------------+-------------------------------+--------+-------+ + * | perftbl_len | number of entries in perf | 0x8 | 0x4 | + * | | table. A single entry in the | | | + * | | perf table denotes no table | | | + * | | and the entry contains | | | + * | | the maximum perf value | | | + * | | that this vCPU supports. | | | + * | | The guest can request any | | | + * | | value between 1 and max perf | | | + * | | when perftbls are not used. | | | + * +---------------------------------------------+--------+-------+ + * | perftbl_sel | write to this register to | 0xc | 0x4 | + * | | select perf table entry to | | | + * | | read from | | | + * +---------------------------------------------+--------+-------+ + * | perftbl_rd | read this register to get | 0x10 | 0x4 | + * | | perf value of the selected | | | + * | | entry based on perftbl_sel | | | + * +---------------------------------------------+--------+-------+ + * | perf_domain | performance domain number | 0x14 | 0x4 | + * | | that this vCPU belongs to. | | | + * | | vCPUs sharing the same perf | | | + * | | domain number are part of the | | | + * | | same performance domain. | | | + * +-------------+-------------------------------+--------+-------+ + */ + +#define REG_CUR_PERF_STATE_OFFSET 0x0 +#define REG_SET_PERF_STATE_OFFSET 0x4 +#define REG_PERFTBL_LEN_OFFSET 0x8 +#define REG_PERFTBL_SEL_OFFSET 0xc +#define REG_PERFTBL_RD_OFFSET 0x10 +#define REG_PERF_DOMAIN_OFFSET 0x14 +#define PER_CPU_OFFSET 0x1000 + +#define PERFTBL_MAX_ENTRIES 64U + +static void __iomem *base; +static DEFINE_PER_CPU(u32, perftbl_num_entries); + +static void virt_scale_freq_tick(void) +{ + int cpu = smp_processor_id(); + u32 max_freq = (u32)cpufreq_get_hw_max_freq(cpu); + u64 cur_freq; + unsigned long scale; + + cur_freq = (u64)readl_relaxed(base + cpu * PER_CPU_OFFSET + + REG_CUR_PERF_STATE_OFFSET); + + cur_freq <<= SCHED_CAPACITY_SHIFT; + scale = (unsigned long)div_u64(cur_freq, max_freq); + scale = min(scale, SCHED_CAPACITY_SCALE); + + this_cpu_write(arch_freq_scale, scale); +} + +static struct scale_freq_data virt_sfd = { + .source = SCALE_FREQ_SOURCE_VIRT, + .set_freq_scale = virt_scale_freq_tick, +}; + +static unsigned int virt_cpufreq_set_perf(struct cpufreq_policy *policy, + unsigned int target_freq) +{ + writel_relaxed(target_freq, + base + policy->cpu * PER_CPU_OFFSET + REG_SET_PERF_STATE_OFFSET); + return 0; +} + +static unsigned int virt_cpufreq_fast_switch(struct cpufreq_policy *policy, + unsigned int target_freq) +{ + virt_cpufreq_set_perf(policy, target_freq); + return target_freq; +} + +static u32 virt_cpufreq_get_perftbl_entry(int cpu, u32 idx) +{ + writel_relaxed(idx, base + cpu * PER_CPU_OFFSET + + REG_PERFTBL_SEL_OFFSET); + return readl_relaxed(base + cpu * PER_CPU_OFFSET + + REG_PERFTBL_RD_OFFSET); +} + +static int virt_cpufreq_target(struct cpufreq_policy *policy, + unsigned int target_freq, + unsigned int relation) +{ + struct cpufreq_freqs freqs; + int ret = 0; + + freqs.old = policy->cur; + freqs.new = target_freq; + + cpufreq_freq_transition_begin(policy, &freqs); + ret = virt_cpufreq_set_perf(policy, target_freq); + cpufreq_freq_transition_end(policy, &freqs, ret != 0); + + return ret; +} + +static int virt_cpufreq_get_sharing_cpus(struct cpufreq_policy *policy) +{ + u32 cur_perf_domain, perf_domain; + struct device *cpu_dev; + int cpu; + + cur_perf_domain = readl_relaxed(base + policy->cpu * + PER_CPU_OFFSET + REG_PERF_DOMAIN_OFFSET); + + for_each_possible_cpu(cpu) { + cpu_dev = get_cpu_device(cpu); + if (!cpu_dev) + continue; + + perf_domain = readl_relaxed(base + cpu * + PER_CPU_OFFSET + REG_PERF_DOMAIN_OFFSET); + + if (perf_domain == cur_perf_domain) + cpumask_set_cpu(cpu, policy->cpus); + } + + return 0; +} + +static int virt_cpufreq_get_freq_info(struct cpufreq_policy *policy) +{ + struct cpufreq_frequency_table *table; + u32 num_perftbl_entries, idx; + + num_perftbl_entries = per_cpu(perftbl_num_entries, policy->cpu); + + if (num_perftbl_entries == 1) { + policy->cpuinfo.min_freq = 1; + policy->cpuinfo.max_freq = virt_cpufreq_get_perftbl_entry(policy->cpu, 0); + + policy->min = policy->cpuinfo.min_freq; + policy->max = policy->cpuinfo.max_freq; + + policy->cur = policy->max; + return 0; + } + + table = kcalloc(num_perftbl_entries + 1, sizeof(*table), GFP_KERNEL); + if (!table) + return -ENOMEM; + + for (idx = 0; idx < num_perftbl_entries; idx++) + table[idx].frequency = virt_cpufreq_get_perftbl_entry(policy->cpu, idx); + + table[idx].frequency = CPUFREQ_TABLE_END; + policy->freq_table = table; + + return 0; +} + +static int virt_cpufreq_cpu_init(struct cpufreq_policy *policy) +{ + struct device *cpu_dev; + int ret; + + cpu_dev = get_cpu_device(policy->cpu); + if (!cpu_dev) + return -ENODEV; + + ret = virt_cpufreq_get_freq_info(policy); + if (ret) { + dev_warn(cpu_dev, "failed to get cpufreq info\n"); + return ret; + } + + ret = virt_cpufreq_get_sharing_cpus(policy); + if (ret) { + dev_warn(cpu_dev, "failed to get sharing cpumask\n"); + return ret; + } + + /* + * To simplify and improve latency of handling frequency requests on + * the host side, this ensures that the vCPU thread triggering the MMIO + * abort is the same thread whose performance constraints (Ex. uclamp + * settings) need to be updated. This simplifies the VMM (Virtual + * Machine Manager) having to find the correct vCPU thread and/or + * facing permission issues when configuring other threads. + */ + policy->dvfs_possible_from_any_cpu = false; + policy->fast_switch_possible = true; + + /* + * Using the default SCALE_FREQ_SOURCE_CPUFREQ is insufficient since + * the actual physical CPU frequency may not match requested frequency + * from the vCPU thread due to frequency update latencies or other + * inputs to the physical CPU frequency selection. This additional FIE + * source allows for more accurate freq_scale updates and only takes + * effect if another FIE source such as AMUs have not been registered. + */ + topology_set_scale_freq_source(&virt_sfd, policy->cpus); + + return 0; +} + +static void virt_cpufreq_cpu_exit(struct cpufreq_policy *policy) +{ + topology_clear_scale_freq_source(SCALE_FREQ_SOURCE_VIRT, policy->related_cpus); + kfree(policy->freq_table); +} + +static int virt_cpufreq_online(struct cpufreq_policy *policy) +{ + /* Nothing to restore. */ + return 0; +} + +static int virt_cpufreq_offline(struct cpufreq_policy *policy) +{ + /* Dummy offline() to avoid exit() being called and freeing resources. */ + return 0; +} + +static int virt_cpufreq_verify_policy(struct cpufreq_policy_data *policy) +{ + if (policy->freq_table) + return cpufreq_frequency_table_verify(policy, policy->freq_table); + + cpufreq_verify_within_cpu_limits(policy); + return 0; +} + +static struct cpufreq_driver cpufreq_virt_driver = { + .name = "virt-cpufreq", + .init = virt_cpufreq_cpu_init, + .exit = virt_cpufreq_cpu_exit, + .online = virt_cpufreq_online, + .offline = virt_cpufreq_offline, + .verify = virt_cpufreq_verify_policy, + .target = virt_cpufreq_target, + .fast_switch = virt_cpufreq_fast_switch, + .attr = cpufreq_generic_attr, +}; + +static int virt_cpufreq_driver_probe(struct platform_device *pdev) +{ + u32 num_perftbl_entries; + int ret, cpu; + + base = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(base)) + return PTR_ERR(base); + + for_each_possible_cpu(cpu) { + num_perftbl_entries = readl_relaxed(base + cpu * PER_CPU_OFFSET + + REG_PERFTBL_LEN_OFFSET); + + if (!num_perftbl_entries || num_perftbl_entries > PERFTBL_MAX_ENTRIES) + return -ENODEV; + + per_cpu(perftbl_num_entries, cpu) = num_perftbl_entries; + } + + ret = cpufreq_register_driver(&cpufreq_virt_driver); + if (ret) { + dev_err(&pdev->dev, "Virtual CPUFreq driver failed to register: %d\n", ret); + return ret; + } + + dev_dbg(&pdev->dev, "Virtual CPUFreq driver initialized\n"); + return 0; +} + +static void virt_cpufreq_driver_remove(struct platform_device *pdev) +{ + cpufreq_unregister_driver(&cpufreq_virt_driver); +} + +static const struct of_device_id virt_cpufreq_match[] = { + { .compatible = "qemu,virtual-cpufreq", .data = NULL}, + {} +}; +MODULE_DEVICE_TABLE(of, virt_cpufreq_match); + +static struct platform_driver virt_cpufreq_driver = { + .probe = virt_cpufreq_driver_probe, + .remove = virt_cpufreq_driver_remove, + .driver = { + .name = "virt-cpufreq", + .of_match_table = virt_cpufreq_match, + }, +}; + +static int __init virt_cpufreq_init(void) +{ + return platform_driver_register(&virt_cpufreq_driver); +} +postcore_initcall(virt_cpufreq_init); + +static void __exit virt_cpufreq_exit(void) +{ + platform_driver_unregister(&virt_cpufreq_driver); +} +module_exit(virt_cpufreq_exit); + +MODULE_DESCRIPTION("Virtual cpufreq driver"); +MODULE_LICENSE("GPL"); diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h index b721f360d759..d5d848849408 100644 --- a/include/linux/arch_topology.h +++ b/include/linux/arch_topology.h @@ -49,6 +49,7 @@ enum scale_freq_source { SCALE_FREQ_SOURCE_CPUFREQ = 0, SCALE_FREQ_SOURCE_ARCH, SCALE_FREQ_SOURCE_CPPC, + SCALE_FREQ_SOURCE_VIRT, }; struct scale_freq_data {