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Message-ID: <20250227021855.3257188-39-seanjc@google.com>
Date: Wed, 26 Feb 2025 18:18:54 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Paolo Bonzini <pbonzini@...hat.com>,
Sean Christopherson <seanjc@...gle.com>, Juergen Gross <jgross@...e.com>,
"K. Y. Srinivasan" <kys@...rosoft.com>, Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
Dexuan Cui <decui@...rosoft.com>, Ajay Kaher <ajay.kaher@...adcom.com>,
Jan Kiszka <jan.kiszka@...mens.com>, Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>, Daniel Lezcano <daniel.lezcano@...aro.org>,
John Stultz <jstultz@...gle.com>
Cc: linux-kernel@...r.kernel.org, linux-coco@...ts.linux.dev,
kvm@...r.kernel.org, virtualization@...ts.linux.dev,
linux-hyperv@...r.kernel.org, xen-devel@...ts.xenproject.org,
Tom Lendacky <thomas.lendacky@....com>, Nikunj A Dadhania <nikunj@....com>
Subject: [PATCH v2 38/38] x86/paravirt: kvmclock: Setup kvmclock early iff
it's sched_clock
Rework the seemingly generic x86_cpuinit_ops.early_percpu_clock_init hook
into a dedicated PV sched_clock hook, as the only reason the hook exists
is to allow kvmclock to enable its PV clock on secondary CPUs before the
kernel tries to reference sched_clock, e.g. when grabbing a timestamp for
printk.
Rearranging the hook doesn't exactly reduce complexity; arguably it does
the opposite. But as-is, it's practically impossible to understand *why*
kvmclock needs to do early configuration.
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
arch/x86/include/asm/paravirt.h | 10 ++++++++--
arch/x86/include/asm/x86_init.h | 2 --
arch/x86/kernel/kvmclock.c | 13 ++++++-------
arch/x86/kernel/paravirt.c | 18 +++++++++++++++++-
arch/x86/kernel/smpboot.c | 2 +-
arch/x86/kernel/x86_init.c | 1 -
6 files changed, 32 insertions(+), 14 deletions(-)
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index 5de31b22aa5f..8550262fc710 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -29,13 +29,14 @@ DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
DECLARE_STATIC_CALL(pv_sched_clock, dummy_sched_clock);
int __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable,
- void (*save)(void), void (*restore)(void));
+ void (*save)(void), void (*restore)(void),
+ void (*start_secondary));
static __always_inline void paravirt_set_sched_clock(u64 (*func)(void),
void (*save)(void),
void (*restore)(void))
{
- (void)__paravirt_set_sched_clock(func, true, save, restore);
+ (void)__paravirt_set_sched_clock(func, true, save, restore, NULL);
}
static __always_inline u64 paravirt_sched_clock(void)
@@ -43,6 +44,8 @@ static __always_inline u64 paravirt_sched_clock(void)
return static_call(pv_sched_clock)();
}
+void paravirt_sched_clock_start_secondary(void);
+
struct static_key;
extern struct static_key paravirt_steal_enabled;
extern struct static_key paravirt_steal_rq_enabled;
@@ -756,6 +759,9 @@ void native_pv_lock_init(void) __init;
static inline void native_pv_lock_init(void)
{
}
+static inline void paravirt_sched_clock_start_secondary(void)
+{
+}
#endif
#endif /* !CONFIG_PARAVIRT */
diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 213cf5379a5a..e3456def5aea 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -187,13 +187,11 @@ struct x86_init_ops {
/**
* struct x86_cpuinit_ops - platform specific cpu hotplug setups
* @setup_percpu_clockev: set up the per cpu clock event device
- * @early_percpu_clock_init: early init of the per cpu clock event device
* @fixup_cpu_id: fixup function for cpuinfo_x86::topo.pkg_id
* @parallel_bringup: Parallel bringup control
*/
struct x86_cpuinit_ops {
void (*setup_percpu_clockev)(void);
- void (*early_percpu_clock_init)(void);
void (*fixup_cpu_id)(struct cpuinfo_x86 *c, int node);
bool parallel_bringup;
};
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index 280bb964f30a..11f078b91f22 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -126,12 +126,13 @@ static void kvm_save_sched_clock_state(void)
kvmclock_disable();
}
-#ifdef CONFIG_SMP
-static void kvm_setup_secondary_clock(void)
+static void kvm_setup_secondary_sched_clock(void)
{
+ if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_SMP)))
+ return;
+
kvm_register_clock("secondary cpu, sched_clock setup");
}
-#endif
static void kvm_restore_sched_clock_state(void)
{
@@ -367,7 +368,8 @@ static void __init kvm_sched_clock_init(bool stable)
{
if (__paravirt_set_sched_clock(kvm_sched_clock_read, stable,
kvm_save_sched_clock_state,
- kvm_restore_sched_clock_state))
+ kvm_restore_sched_clock_state,
+ kvm_setup_secondary_sched_clock))
return;
kvm_sched_clock_offset = kvm_clock_read();
@@ -452,9 +454,6 @@ void __init kvmclock_init(void)
x86_platform.get_wallclock = kvm_get_wallclock;
x86_platform.set_wallclock = kvm_set_wallclock;
-#ifdef CONFIG_SMP
- x86_cpuinit.early_percpu_clock_init = kvm_setup_secondary_clock;
-#endif
kvm_get_preset_lpj();
clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index c538c608d9fb..f93278ddb1d2 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -86,8 +86,13 @@ static u64 native_steal_clock(int cpu)
DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
DEFINE_STATIC_CALL(pv_sched_clock, native_sched_clock);
+#ifdef CONFIG_SMP
+static void (*pv_sched_clock_start_secondary)(void) __ro_after_init;
+#endif
+
int __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable,
- void (*save)(void), void (*restore)(void))
+ void (*save)(void), void (*restore)(void),
+ void (*start_secondary))
{
/*
* Don't replace TSC with a PV clock when running as a CoCo guest and
@@ -104,9 +109,20 @@ int __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable,
static_call_update(pv_sched_clock, func);
x86_platform.save_sched_clock_state = save;
x86_platform.restore_sched_clock_state = restore;
+#ifdef CONFIG_SMP
+ pv_sched_clock_start_secondary = start_secondary;
+#endif
return 0;
}
+#ifdef CONFIG_SMP
+void paravirt_sched_clock_start_secondary(void)
+{
+ if (pv_sched_clock_start_secondary)
+ pv_sched_clock_start_secondary();
+}
+#endif
+
/* These are in entry.S */
static struct resource reserve_ioports = {
.start = 0,
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index c10850ae6f09..e6fff67dd264 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -278,7 +278,7 @@ static void notrace start_secondary(void *unused)
cpu_init();
fpu__init_cpu();
rcutree_report_cpu_starting(raw_smp_processor_id());
- x86_cpuinit.early_percpu_clock_init();
+ paravirt_sched_clock_start_secondary();
ap_starting();
diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index 0a2bbd674a6d..1d4cf071c74b 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -128,7 +128,6 @@ struct x86_init_ops x86_init __initdata = {
};
struct x86_cpuinit_ops x86_cpuinit = {
- .early_percpu_clock_init = x86_init_noop,
.setup_percpu_clockev = setup_secondary_APIC_clock,
.parallel_bringup = true,
};
--
2.48.1.711.g2feabab25a-goog
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