linux-kernel - [PATCH v2 15/38] x86/xen/time: Nullify x86_platform's sched

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Message-ID: <20250227021855.3257188-16-seanjc@google.com>
Date: Wed, 26 Feb 2025 18:18:31 -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 15/38] x86/xen/time: Nullify x86_platform's sched_clock
 save/restore hooks

Nullify 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@...gle.com>
---
 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 9e2e900dc0c7..51eba986cd18 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -565,6 +565,12 @@ 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 = NULL;
+	x86_platform.restore_sched_clock_state = NULL;
 
 	tsc_register_calibration_routines(xen_tsc_khz, NULL);
 	x86_platform.get_wallclock = xen_get_wallclock;
-- 
2.48.1.711.g2feabab25a-goog