On Tue, Jul 9, 2024 at 5:08 PM Saravana Kannan <saravanak@xxxxxxxxxx> wrote: > > On Fri, Jun 28, 2024 at 5:01 AM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: > > > > Hi, > > > > On Thu, Jun 27, 2024 at 11:22 PM David Dai <davidai@xxxxxxxxxx> wrote: > > > > > > Hi folks, > > > > > > Gentle nudge on this patch to see if there's any remaining concerns? > > > > Yes, there are. > > > > The dependency of OF is pretty much a no-go from my perspective. > > If you are talking about the "depends on OF" I think that can and > should be dropped. > > There's nothing really OF specific about this driver except the probe > function being for a platform device/driver. We can easily write an > ACPI driver variant of the probe function and have the same driver > work for both OF and ACPI versions of the device. We don't have any > ACPI experience or a test set up to test the ACPI variant. That's why > we haven't added it. We are more than happy to accept tested patches > on top of this that'll enable this for ACPI variants too. > > If we drop the "depends on OF", will you accept this patch? If not, > can you give some guidance on what you are looking for? Hi Rafael, Just wanted to follow up and see what your thoughts are on this? Thanks, David > > Thanks, > Saravana > > > > > > > > Thanks! > > > > > > > On Mon, May 20, 2024 at 10:32 PM David Dai <davidai@xxxxxxxxxx> wrote: > > > > > > > > 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 <saravanak@xxxxxxxxxx> > > > > Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx> > > > > Signed-off-by: David Dai <davidai@xxxxxxxxxx> > > > > --- > > > > drivers/cpufreq/Kconfig | 14 ++ > > > > drivers/cpufreq/Makefile | 1 + > > > > drivers/cpufreq/virtual-cpufreq.c | 335 ++++++++++++++++++++++++++++++ > > > > include/linux/arch_topology.h | 1 + > > > > 4 files changed, 351 insertions(+) > > > > create mode 100644 drivers/cpufreq/virtual-cpufreq.c > > > > > > > > diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig > > > > index 94e55c40970a..9aa86bec5793 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 OF && 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 8d141c71b016..eb72ecdc24db 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..59ce2bda3913 > > > > --- /dev/null > > > > +++ b/drivers/cpufreq/virtual-cpufreq.c > > > > @@ -0,0 +1,335 @@ > > > > +// SPDX-License-Identifier: GPL-2.0-only > > > > +/* > > > > + * Copyright (C) 2024 Google LLC > > > > + */ > > > > + > > > > +#include <linux/arch_topology.h> > > > > +#include <linux/cpufreq.h> > > > > +#include <linux/init.h> > > > > +#include <linux/sched.h> > > > > +#include <linux/kernel.h> > > > > +#include <linux/module.h> > > > > +#include <linux/of_address.h> > > > > +#include <linux/of_platform.h> > > > > +#include <linux/platform_device.h> > > > > +#include <linux/slab.h> > > > > + > > > > +/* > > > > + * 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 int virt_cpufreq_cpu_exit(struct cpufreq_policy *policy) > > > > +{ > > > > + topology_clear_scale_freq_source(SCALE_FREQ_SOURCE_VIRT, policy->related_cpus); > > > > + kfree(policy->freq_table); > > > > + return 0; > > > > +} > > > > + > > > > +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 int virt_cpufreq_driver_remove(struct platform_device *pdev) > > > > +{ > > > > + cpufreq_unregister_driver(&cpufreq_virt_driver); > > > > + return 0; > > > > +} > > > > + > > > > +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 { > > > > -- > > > > 2.45.0.215.g3402c0e53f-goog > > > > > > >