c->x86_phys_bits -= keyid_bits;
}
-static void init_intel_energy_perf(struct cpuinfo_x86 *c)
-{
- u64 epb;
-
- /*
- * Initialize MSR_IA32_ENERGY_PERF_BIAS if not already initialized.
- * (x86_energy_perf_policy(8) is available to change it at run-time.)
- */
- if (!cpu_has(c, X86_FEATURE_EPB))
- return;
-
- rdmsrl(MSR_IA32_ENERGY_PERF_BIAS, epb);
- if ((epb & 0xF) != ENERGY_PERF_BIAS_PERFORMANCE)
- return;
-
- pr_warn_once("ENERGY_PERF_BIAS: Set to 'normal', was 'performance'\n");
- pr_warn_once("ENERGY_PERF_BIAS: View and update with x86_energy_perf_policy(8)\n");
- epb = (epb & ~0xF) | ENERGY_PERF_BIAS_NORMAL;
- wrmsrl(MSR_IA32_ENERGY_PERF_BIAS, epb);
-}
-
-static void intel_bsp_resume(struct cpuinfo_x86 *c)
-{
- /*
- * MSR_IA32_ENERGY_PERF_BIAS is lost across suspend/resume,
- * so reinitialize it properly like during bootup:
- */
- init_intel_energy_perf(c);
-}
-
static void init_cpuid_fault(struct cpuinfo_x86 *c)
{
u64 msr;
if (cpu_has(c, X86_FEATURE_TME))
detect_tme(c);
- init_intel_energy_perf(c);
-
init_intel_misc_features(c);
}
.c_detect_tlb = intel_detect_tlb,
.c_early_init = early_init_intel,
.c_init = init_intel,
- .c_bsp_resume = intel_bsp_resume,
.c_x86_vendor = X86_VENDOR_INTEL,
};
cpu_dev_register(intel_cpu_dev);
-
--- /dev/null
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Intel Performance and Energy Bias Hint support.
+ *
+ * Copyright (C) 2019 Intel Corporation
+ *
+ * Author:
+ * Rafael J. Wysocki <rafael.j.wysocki@intel.com>
+ */
+
+#include <linux/cpuhotplug.h>
+#include <linux/kernel.h>
+#include <linux/syscore_ops.h>
+
+#include <asm/cpufeature.h>
+#include <asm/msr.h>
+
+/**
+ * DOC: overview
+ *
+ * The Performance and Energy Bias Hint (EPB) allows software to specify its
+ * preference with respect to the power-performance tradeoffs present in the
+ * processor. Generally, the EPB is expected to be set by user space through
+ * the generic MSR interface (with the help of the x86_energy_perf_policy tool),
+ * but there are two reasons for the kernel to touch it.
+ *
+ * First, there are systems where the platform firmware resets the EPB during
+ * system-wide transitions from sleep states back into the working state
+ * effectively causing the previous EPB updates by user space to be lost.
+ * Thus the kernel needs to save the current EPB values for all CPUs during
+ * system-wide transitions to sleep states and restore them on the way back to
+ * the working state. That can be achieved by saving EPB for secondary CPUs
+ * when they are taken offline during transitions into system sleep states and
+ * for the boot CPU in a syscore suspend operation, so that it can be restored
+ * for the boot CPU in a syscore resume operation and for the other CPUs when
+ * they are brought back online. However, CPUs that are already offline when
+ * a system-wide PM transition is started are not taken offline again, but their
+ * EPB values may still be reset by the platform firmware during the transition,
+ * so in fact it is necessary to save the EPB of any CPU taken offline and to
+ * restore it when the given CPU goes back online at all times.
+ *
+ * Second, on many systems the initial EPB value coming from the platform
+ * firmware is 0 ('performance') and at least on some of them that is because
+ * the platform firmware does not initialize EPB at all with the assumption that
+ * the OS will do that anyway. That sometimes is problematic, as it may cause
+ * the system battery to drain too fast, for example, so it is better to adjust
+ * it on CPU bring-up and if the initial EPB value for a given CPU is 0, the
+ * kernel changes it to 6 ('normal').
+ */
+
+static DEFINE_PER_CPU(u8, saved_epb);
+
+#define EPB_MASK 0x0fULL
+#define EPB_SAVED 0x10ULL
+
+static int intel_epb_save(void)
+{
+ u64 epb;
+
+ rdmsrl(MSR_IA32_ENERGY_PERF_BIAS, epb);
+ /*
+ * Ensure that saved_epb will always be nonzero after this write even if
+ * the EPB value read from the MSR is 0.
+ */
+ this_cpu_write(saved_epb, (epb & EPB_MASK) | EPB_SAVED);
+
+ return 0;
+}
+
+static void intel_epb_restore(void)
+{
+ u64 val = this_cpu_read(saved_epb);
+ u64 epb;
+
+ rdmsrl(MSR_IA32_ENERGY_PERF_BIAS, epb);
+ if (val) {
+ val &= EPB_MASK;
+ } else {
+ /*
+ * Because intel_epb_save() has not run for the current CPU yet,
+ * it is going online for the first time, so if its EPB value is
+ * 0 ('performance') at this point, assume that it has not been
+ * initialized by the platform firmware and set it to 6
+ * ('normal').
+ */
+ val = epb & EPB_MASK;
+ if (val == ENERGY_PERF_BIAS_PERFORMANCE) {
+ val = ENERGY_PERF_BIAS_NORMAL;
+ pr_warn_once("ENERGY_PERF_BIAS: Set to 'normal', was 'performance'\n");
+ }
+ }
+ wrmsrl(MSR_IA32_ENERGY_PERF_BIAS, (epb & ~EPB_MASK) | val);
+}
+
+static struct syscore_ops intel_epb_syscore_ops = {
+ .suspend = intel_epb_save,
+ .resume = intel_epb_restore,
+};
+
+static int intel_epb_online(unsigned int cpu)
+{
+ intel_epb_restore();
+ return 0;
+}
+
+static int intel_epb_offline(unsigned int cpu)
+{
+ return intel_epb_save();
+}
+
+static __init int intel_epb_init(void)
+{
+ int ret;
+
+ if (!boot_cpu_has(X86_FEATURE_EPB))
+ return -ENODEV;
+
+ ret = cpuhp_setup_state(CPUHP_AP_X86_INTEL_EPB_ONLINE,
+ "x86/intel/epb:online", intel_epb_online,
+ intel_epb_offline);
+ if (ret < 0)
+ goto err_out_online;
+
+ register_syscore_ops(&intel_epb_syscore_ops);
+ return 0;
+
+err_out_online:
+ cpuhp_remove_state(CPUHP_AP_X86_INTEL_EPB_ONLINE);
+ return ret;
+}
+subsys_initcall(intel_epb_init);
projects / linux.git / commitdiff