From da0e58c038e60e7e65d30813ebdfe91687aa8a24 Mon Sep 17 00:00:00 2001 From: Artem Bityutskiy Date: Wed, 2 Mar 2022 10:15:59 +0200 Subject: [PATCH] intel_idle: add 'preferred_cstates' module argument On Sapphire Rapids Xeon (SPR) the C1 and C1E states are basically mutually exclusive - only one of them can be enabled. By default, 'intel_idle' driver enables C1 and disables C1E. However, some users prefer to use C1E instead of C1, because it saves more energy. This patch adds a new module parameter ('preferred_cstates') for enabling C1E and disabling C1. Here is the idea behind it. 1. This option has effect only for "mutually exclusive" C-states like C1 and C1E on SPR. 2. It does not have any effect on independent C-states, which do not require other C-states to be disabled (most states on most platforms as of today). 3. For mutually exclusive C-states, the 'intel_idle' driver always has a reasonable default, such as enabling C1 on SPR by default. On other platforms, the default may be different. 4. Users can override the default using the 'preferred_cstates' parameter. 5. The parameter accepts the preferred C-states bit-mask, similarly to the existing 'states_off' parameter. 6. This parameter is not limited to C1/C1E, and leaves room for supporting other mutually exclusive C-states, if they come in the future. Today 'intel_idle' can only be compiled-in, which means that on SPR, in order to disable C1 and enable C1E, users should boot with the following kernel argument: intel_idle.preferred_cstates=4 Signed-off-by: Artem Bityutskiy Signed-off-by: Rafael J. Wysocki --- drivers/idle/intel_idle.c | 46 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c index 1c7c25909e54..b2688c326522 100644 --- a/drivers/idle/intel_idle.c +++ b/drivers/idle/intel_idle.c @@ -64,6 +64,7 @@ static struct cpuidle_driver intel_idle_driver = { /* intel_idle.max_cstate=0 disables driver */ static int max_cstate = CPUIDLE_STATE_MAX - 1; static unsigned int disabled_states_mask; +static unsigned int preferred_states_mask; static struct cpuidle_device __percpu *intel_idle_cpuidle_devices; @@ -1400,6 +1401,8 @@ static inline void intel_idle_init_cstates_acpi(struct cpuidle_driver *drv) { } static inline bool intel_idle_off_by_default(u32 mwait_hint) { return false; } #endif /* !CONFIG_ACPI_PROCESSOR_CSTATE */ +static void c1e_promotion_enable(void); + /** * ivt_idle_state_table_update - Tune the idle states table for Ivy Town. * @@ -1570,6 +1573,26 @@ static void __init skx_idle_state_table_update(void) } } +/** + * spr_idle_state_table_update - Adjust Sapphire Rapids idle states table. + */ +static void __init spr_idle_state_table_update(void) +{ + /* Check if user prefers C1E over C1. */ + if (preferred_states_mask & BIT(2)) { + if (preferred_states_mask & BIT(1)) + /* Both can't be enabled, stick to the defaults. */ + return; + + spr_cstates[0].flags |= CPUIDLE_FLAG_UNUSABLE; + spr_cstates[1].flags &= ~CPUIDLE_FLAG_UNUSABLE; + + /* Enable C1E using the "C1E promotion" bit. */ + c1e_promotion_enable(); + disable_promotion_to_c1e = false; + } +} + static bool __init intel_idle_verify_cstate(unsigned int mwait_hint) { unsigned int mwait_cstate = MWAIT_HINT2CSTATE(mwait_hint) + 1; @@ -1604,6 +1627,9 @@ static void __init intel_idle_init_cstates_icpu(struct cpuidle_driver *drv) case INTEL_FAM6_SKYLAKE_X: skx_idle_state_table_update(); break; + case INTEL_FAM6_SAPPHIRERAPIDS_X: + spr_idle_state_table_update(); + break; } for (cstate = 0; cstate < CPUIDLE_STATE_MAX; ++cstate) { @@ -1676,6 +1702,15 @@ static void auto_demotion_disable(void) wrmsrl(MSR_PKG_CST_CONFIG_CONTROL, msr_bits); } +static void c1e_promotion_enable(void) +{ + unsigned long long msr_bits; + + rdmsrl(MSR_IA32_POWER_CTL, msr_bits); + msr_bits |= 0x2; + wrmsrl(MSR_IA32_POWER_CTL, msr_bits); +} + static void c1e_promotion_disable(void) { unsigned long long msr_bits; @@ -1845,3 +1880,14 @@ module_param(max_cstate, int, 0444); */ module_param_named(states_off, disabled_states_mask, uint, 0444); MODULE_PARM_DESC(states_off, "Mask of disabled idle states"); +/* + * Some platforms come with mutually exclusive C-states, so that if one is + * enabled, the other C-states must not be used. Example: C1 and C1E on + * Sapphire Rapids platform. This parameter allows for selecting the + * preferred C-states among the groups of mutually exclusive C-states - the + * selected C-states will be registered, the other C-states from the mutually + * exclusive group won't be registered. If the platform has no mutually + * exclusive C-states, this parameter has no effect. + */ +module_param_named(preferred_cstates, preferred_states_mask, uint, 0444); +MODULE_PARM_DESC(preferred_cstates, "Mask of preferred idle states");