[PATCH 3/9] x86/mwait-idle: latch struct idle_cpu contents

[Jan Beulich <jbeulich@xxxxxxxx>]

Rather than storing a pointer (and needing to keep all struct instances in
memory post-init), and rather than (like the Linux counterpart has it)
keeping individual variables, simply copy the respective structure
instance. By implication, subsequent updates now need doing to the copy.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -107,14 +107,14 @@ struct idle_cpu {
        enum c1e_promotion c1e_promotion;
 };
 
-static const struct idle_cpu *__ro_after_init icpu;
+static struct idle_cpu __ro_after_init icpu;
 
-static const struct cpuidle_state {
+struct cpuidle_state {
        char            name[16];
        unsigned int    flags;
        unsigned int    exit_latency; /* in US */
        unsigned int    target_residency; /* in US */
-} *__ro_after_init cpuidle_state_table;
+};
 
 #define CPUIDLE_FLAG_DISABLED          0x1
 /*
@@ -1097,7 +1097,7 @@ static void cf_check mwait_idle(void)
         * leave_mm() to avoid costly and often unnecessary wakeups
         * for flushing the user TLB's associated with the active mm.
         */
-       if (cpuidle_state_table[].flags & CPUIDLE_FLAG_TLB_FLUSHED)
+       if (icpu.state_table[].flags & CPUIDLE_FLAG_TLB_FLUSHED)
                leave_mm(cpu);
 #endif
 
@@ -1139,7 +1139,7 @@ static void cf_check auto_demotion_disab
        u64 msr_bits;
 
        rdmsrl(MSR_PKG_CST_CONFIG_CONTROL, msr_bits);
-       msr_bits &= ~(icpu->auto_demotion_disable_flags);
+       msr_bits &= ~icpu.auto_demotion_disable_flags;
        wrmsrl(MSR_PKG_CST_CONFIG_CONTROL, msr_bits);
 }
 
@@ -1371,10 +1371,10 @@ static void __init ivt_idle_state_table_
                /* 1 and 2 socket systems use default ivt_cstates */
                break;
        case 2: case 3:
-               cpuidle_state_table = ivt_cstates_4s;
+               icpu.state_table = ivt_cstates_4s;
                break;
        default:
-               cpuidle_state_table = ivt_cstates_8s;
+               icpu.state_table = ivt_cstates_8s;
                break;
        }
 }
@@ -1525,14 +1525,12 @@ static void __init adl_idle_state_table_
                adl_l_cstates[1].flags |= CPUIDLE_FLAG_DISABLED;
 
                /* Disable C1E by clearing the "C1E promotion" bit. */
-               idle_cpu_adl.c1e_promotion = C1E_PROMOTION_DISABLE;
-               idle_cpu_adl_l.c1e_promotion = C1E_PROMOTION_DISABLE;
+               icpu.c1e_promotion = C1E_PROMOTION_DISABLE;
                return;
        }
 
        /* Make sure C1E is enabled by default */
-       idle_cpu_adl.c1e_promotion = C1E_PROMOTION_ENABLE;
-       idle_cpu_adl_l.c1e_promotion = C1E_PROMOTION_ENABLE;
+       icpu.c1e_promotion = C1E_PROMOTION_ENABLE;
 }
 
 /*
@@ -1593,6 +1591,7 @@ static int __init mwait_idle_probe(void)
 {
        unsigned int eax, ebx, ecx;
        const struct x86_cpu_id *id;
+       const struct idle_cpu *idle_cpu;
        const char *str;
 
        if (boot_cpu_data.vendor != X86_VENDOR_INTEL)
@@ -1627,8 +1626,8 @@ static int __init mwait_idle_probe(void)
 
        pr_debug(PREFIX "MWAIT substates: %#x\n", mwait_substates);
 
-       icpu = id->driver_data;
-       cpuidle_state_table = icpu->state_table;
+       idle_cpu = id->driver_data;
+       icpu = *idle_cpu;
 
        if (boot_cpu_has(X86_FEATURE_XEN_ARAT))
                lapic_timer_reliable_states = LAPIC_TIMER_ALWAYS_RELIABLE;
@@ -1647,7 +1646,7 @@ static int __init mwait_idle_probe(void)
                const char *ss;
 
                do {
-                       const struct cpuidle_state *state = icpu->state_table;
+                       const struct cpuidle_state *state = 
idle_cpu->state_table;
                        unsigned int bit = 1;
 
                        ss = strchr(str, ',');
@@ -1679,10 +1678,10 @@ static int __init mwait_idle_probe(void)
 
 static void mwait_idle_cpu_tweak(unsigned int cpu, bool bsp)
 {
-       if (icpu->auto_demotion_disable_flags)
+       if (icpu.auto_demotion_disable_flags)
                on_selected_cpus(cpumask_of(cpu), auto_demotion_disable, NULL, 
1);
 
-       switch (icpu->c1e_promotion) {
+       switch (icpu.c1e_promotion) {
        case C1E_PROMOTION_DISABLE:
                on_selected_cpus(cpumask_of(cpu), c1e_promotion_disable, NULL, 
1);
                break;
@@ -1735,11 +1734,11 @@ static int cf_check mwait_idle_cpu_init(
 
        dev->count = 1;
 
-       for (cstate = 0; cpuidle_state_table[cstate].target_residency; 
++cstate) {
+       for (cstate = 0; icpu.state_table[cstate].target_residency; ++cstate) {
                unsigned int num_substates, hint, state;
                struct acpi_processor_cx *cx;
 
-               hint = flg2MWAIT(cpuidle_state_table[cstate].flags);
+               hint = flg2MWAIT(icpu.state_table[cstate].flags);
                state = MWAIT_HINT2CSTATE(hint) + 1;
 
                if (state > max_cstate) {
@@ -1755,10 +1754,10 @@ static int cf_check mwait_idle_cpu_init(
                        continue;
 
                /* if state marked as disabled, skip it */
-               if (cpuidle_state_table[cstate].flags &
+               if (icpu.state_table[cstate].flags &
                    CPUIDLE_FLAG_DISABLED) {
                        printk(XENLOG_DEBUG PREFIX "state %s is disabled\n",
-                              cpuidle_state_table[cstate].name);
+                              icpu.state_table[cstate].name);
                        continue;
                }
 
@@ -1776,15 +1775,15 @@ static int cf_check mwait_idle_cpu_init(
                cx->type = state;
                cx->address = hint;
                cx->entry_method = ACPI_CSTATE_EM_FFH;
-               cx->latency = cpuidle_state_table[cstate].exit_latency;
+               cx->latency = icpu.state_table[cstate].exit_latency;
                cx->target_residency =
-                       cpuidle_state_table[cstate].target_residency;
-               if ((cpuidle_state_table[cstate].flags &
+                       icpu.state_table[cstate].target_residency;
+               if ((icpu.state_table[cstate].flags &
                     CPUIDLE_FLAG_IRQ_ENABLE) &&
                    /* cstate_restore_tsc() needs to be a no-op */
                    boot_cpu_has(X86_FEATURE_NONSTOP_TSC))
                        cx->irq_enable_early = true;
-               if (cpuidle_state_table[cstate].flags & CPUIDLE_FLAG_IBRS)
+               if (icpu.state_table[cstate].flags & CPUIDLE_FLAG_IBRS)
                        cx->ibrs_disable = true;
 
                dev->count++;
@@ -1825,7 +1824,7 @@ int __init mwait_idle_init(struct notifi
 
 void mwait_idle_resume(void)
 {
-       if (!icpu)
+       if (!icpu.state_table)
                return;
 
        mwait_idle_cpu_tweak(smp_processor_id(), true);