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Message-ID: <20230512205256.206394064@linutronix.de>
Date: Fri, 12 May 2023 23:07:19 +0200 (CEST)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: x86@...nel.org, David Woodhouse <dwmw2@...radead.org>,
Andrew Cooper <andrew.cooper3@...rix.com>,
Brian Gerst <brgerst@...il.com>,
Arjan van de Veen <arjan@...ux.intel.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Paul McKenney <paulmck@...nel.org>,
Tom Lendacky <thomas.lendacky@....com>,
Sean Christopherson <seanjc@...gle.com>,
Oleksandr Natalenko <oleksandr@...alenko.name>,
Paul Menzel <pmenzel@...gen.mpg.de>,
"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
Piotr Gorski <lucjan.lucjanov@...il.com>,
Usama Arif <usama.arif@...edance.com>,
Juergen Gross <jgross@...e.com>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
xen-devel@...ts.xenproject.org,
Russell King <linux@...linux.org.uk>,
Arnd Bergmann <arnd@...db.de>,
linux-arm-kernel@...ts.infradead.org,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>, Guo Ren <guoren@...nel.org>,
linux-csky@...r.kernel.org,
Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
linux-mips@...r.kernel.org,
"James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
Helge Deller <deller@....de>, linux-parisc@...r.kernel.org,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
linux-riscv@...ts.infradead.org,
Mark Rutland <mark.rutland@....com>,
Sabin Rapan <sabrapan@...zon.com>,
"Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
Ross Philipson <ross.philipson@...cle.com>
Subject: [patch V4 14/37] x86/smpboot: Remove cpu_callin_mask
From: Thomas Gleixner <tglx@...utronix.de>
Now that TSC synchronization is SMP function call based there is no reason
to wait for the AP to be set in smp_callin_mask. The control CPU waits for
the AP to set itself in the online mask anyway.
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Tested-by: Michael Kelley <mikelley@...rosoft.com>
---
V4: Rename smp_callin() to ap_starting() - Peter Z.
---
arch/x86/kernel/smpboot.c | 74 +++++++++-------------------------------------
1 file changed, 15 insertions(+), 59 deletions(-)
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -104,7 +104,6 @@ EXPORT_PER_CPU_SYMBOL(cpu_info);
/* All of these masks are initialized in setup_cpu_local_masks() */
static cpumask_var_t cpu_initialized_mask;
static cpumask_var_t cpu_callout_mask;
-static cpumask_var_t cpu_callin_mask;
/* Representing CPUs for which sibling maps can be computed */
static cpumask_var_t cpu_sibling_setup_mask;
@@ -161,38 +160,30 @@ static inline void smpboot_restore_warm_
}
-/*
- * Report back to the Boot Processor during boot time or to the caller processor
- * during CPU online.
- */
-static void smp_callin(void)
+/* Run the next set of setup steps for the upcoming CPU */
+static void ap_starting(void)
{
- int cpuid;
-
- /*
- * If waken up by an INIT in an 82489DX configuration
- * cpu_callout_mask guarantees we don't get here before
- * an INIT_deassert IPI reaches our local APIC, so it is
- * now safe to touch our local APIC.
- */
- cpuid = smp_processor_id();
+ int cpuid = smp_processor_id();
/*
- * the boot CPU has finished the init stage and is spinning
- * on callin_map until we finish. We are free to set up this
- * CPU, first the APIC. (this is probably redundant on most
- * boards)
+ * If woken up by an INIT in an 82489DX configuration
+ * cpu_callout_mask guarantees the CPU does not reach this point
+ * before an INIT_deassert IPI reaches the local APIC, so it is now
+ * safe to touch the local APIC.
+ *
+ * Set up this CPU, first the APIC, which is probably redundant on
+ * most boards.
*/
apic_ap_setup();
- /* Save our processor parameters. */
+ /* Save the processor parameters. */
smp_store_cpu_info(cpuid);
/*
* The topology information must be up to date before
* notify_cpu_starting().
*/
- set_cpu_sibling_map(raw_smp_processor_id());
+ set_cpu_sibling_map(cpuid);
ap_init_aperfmperf();
@@ -205,11 +196,6 @@ static void smp_callin(void)
* state CPUHP_ONLINE.
*/
notify_cpu_starting(cpuid);
-
- /*
- * Allow the master to continue.
- */
- cpumask_set_cpu(cpuid, cpu_callin_mask);
}
static void ap_calibrate_delay(void)
@@ -268,12 +254,7 @@ static void notrace start_secondary(void
rcu_cpu_starting(raw_smp_processor_id());
x86_cpuinit.early_percpu_clock_init();
- /*
- * Sync point with wait_cpu_callin(). The AP doesn't wait here
- * but just sets the bit to let the controlling CPU (BSP) know that
- * it's got this far.
- */
- smp_callin();
+ ap_starting();
/* Check TSC synchronization with the control CPU. */
check_tsc_sync_target();
@@ -1109,7 +1090,7 @@ static int wait_cpu_cpumask(unsigned int
* and thus wait_for_master_cpu(), then set cpu_callout_mask to allow it
* to proceed. The AP will then proceed past setting its 'callin' bit
* and end up waiting in check_tsc_sync_target() until we reach
- * do_wait_cpu_online() to tend to it.
+ * wait_cpu_online() to tend to it.
*/
static int wait_cpu_initialized(unsigned int cpu)
{
@@ -1124,20 +1105,7 @@ static int wait_cpu_initialized(unsigned
}
/*
- * Bringup step three: Wait for the target AP to reach smp_callin().
- * The AP is not waiting for us here so we don't need to parallelise
- * this step. Not entirely clear why we care about this, since we just
- * proceed directly to TSC synchronization which is the next sync
- * point with the AP anyway.
- */
-static void wait_cpu_callin(unsigned int cpu)
-{
- while (!cpumask_test_cpu(cpu, cpu_callin_mask))
- schedule();
-}
-
-/*
- * Bringup step four: Wait for the target AP to reach set_cpu_online() in
+ * Bringup step three: Wait for the target AP to reach set_cpu_online() in
* start_secondary().
*/
static void wait_cpu_online(unsigned int cpu)
@@ -1167,14 +1135,6 @@ static int native_kick_ap(unsigned int c
}
/*
- * Already booted CPU?
- */
- if (cpumask_test_cpu(cpu, cpu_callin_mask)) {
- pr_debug("do_boot_cpu %d Already started\n", cpu);
- return -ENOSYS;
- }
-
- /*
* Save current MTRR state in case it was changed since early boot
* (e.g. by the ACPI SMI) to initialize new CPUs with MTRRs in sync:
*/
@@ -1211,7 +1171,6 @@ int native_cpu_up(unsigned int cpu, stru
if (ret)
goto out;
- wait_cpu_callin(cpu);
wait_cpu_online(cpu);
out:
@@ -1327,7 +1286,6 @@ void __init smp_prepare_cpus_common(void
* Setup boot CPU information
*/
smp_store_boot_cpu_info(); /* Final full version of the data */
- cpumask_copy(cpu_callin_mask, cpumask_of(0));
mb();
for_each_possible_cpu(i) {
@@ -1542,7 +1500,6 @@ early_param("possible_cpus", _setup_poss
void __init setup_cpu_local_masks(void)
{
alloc_bootmem_cpumask_var(&cpu_initialized_mask);
- alloc_bootmem_cpumask_var(&cpu_callin_mask);
alloc_bootmem_cpumask_var(&cpu_callout_mask);
alloc_bootmem_cpumask_var(&cpu_sibling_setup_mask);
}
@@ -1606,7 +1563,6 @@ static void remove_cpu_from_maps(int cpu
{
set_cpu_online(cpu, false);
cpumask_clear_cpu(cpu, cpu_callout_mask);
- cpumask_clear_cpu(cpu, cpu_callin_mask);
/* was set by cpu_init() */
cpumask_clear_cpu(cpu, cpu_initialized_mask);
numa_remove_cpu(cpu);
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