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[PATCH v4 30/47] x86/xen/time: NOP-ify x86_platform's sched_clock save/restore hooks
- To: Paolo Bonzini <pbonzini@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, x86@xxxxxxxxxx, Kiryl Shutsemau <kas@xxxxxxxxxx>, Sean Christopherson <seanjc@xxxxxxxxxx>, "K . Y . Srinivasan" <kys@xxxxxxxxxxxxx>, Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>, Wei Liu <wei.liu@xxxxxxxxxx>, Dexuan Cui <decui@xxxxxxxxxxxxx>, Long Li <longli@xxxxxxxxxxxxx>, Ajay Kaher <ajay.kaher@xxxxxxxxxxxx>, Alexey Makhalov <alexey.makhalov@xxxxxxxxxxxx>, Jan Kiszka <jan.kiszka@xxxxxxxxxxx>, Andy Lutomirski <luto@xxxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>, John Stultz <jstultz@xxxxxxxxxx>
- From: Sean Christopherson <seanjc@xxxxxxxxxx>
- Date: Fri, 29 May 2026 08:07:41 -0700
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- Cc: "H . Peter Anvin" <hpa@xxxxxxxxx>, Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>, Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>, Broadcom internal kernel review list <bcm-kernel-feedback-list@xxxxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Stephen Boyd <sboyd@xxxxxxxxxx>, kvm@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-coco@xxxxxxxxxxxxxxx, linux-hyperv@xxxxxxxxxxxxxxx, virtualization@xxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, David Woodhouse <dwmw@xxxxxxxxxxxx>, Tom Lendacky <thomas.lendacky@xxxxxxx>, Nikunj A Dadhania <nikunj@xxxxxxx>, David Woodhouse <dwmw2@xxxxxxxxxxxxx>, Michael Kelley <mhklinux@xxxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>
- Delivery-date: Fri, 29 May 2026 15:12:57 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
NOP-ify the x86_platform sched_clock save/restore hooks when setting up
Xen's PV clock to make it somewhat obvious the hooks aren't used when
running as a Xen guest (Xen uses a paravirtualized suspend/resume flow).
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
arch/x86/xen/time.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 36d66abf5379..640b71d22d97 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -578,6 +578,12 @@ static void __init xen_init_time_common(void)
xen_sched_clock_offset = xen_clocksource_read();
static_call_update(pv_steal_clock, xen_steal_clock);
paravirt_set_sched_clock(xen_sched_clock);
+ /*
+ * Xen has paravirtualized suspend/resume and so doesn't use the common
+ * x86 sched_clock save/restore hooks.
+ */
+ x86_platform.save_sched_clock_state = x86_init_noop;
+ x86_platform.restore_sched_clock_state = x86_init_noop;
x86_init.hyper.get_tsc_khz = xen_tsc_khz;
x86_platform.get_wallclock = xen_get_wallclock;
--
2.54.0.823.g6e5bcc1fc9-goog
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