From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B0DFB42C4A5 for ; Wed, 1 Jul 2026 19:33:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782934407; cv=none; b=XE99jDyZs6u7Qfk57sBIrFVHwoDHfBw+glSVjmNnk6bb3mqQYr7+52MhEVrajzElVwobeXmwYmbbrI0rPb5Fhq2KfGwzA2eHTt8ManaU/IqqhrM+oxldfIytnLY5T9dxMDBs3IK0GrhHmiOZdU04FUiOc0qPTTqFlPRqedoxIs4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782934407; c=relaxed/simple; bh=IG2Hmi12vLvJIelcQEMDYixsIVkPyLQSG2OhagBXg7k=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=e+j7qvE73CtARlXY4cOyfyAreVdfoOko2u5vX9iBMuopsSOcGdcLCkPLnQWH4EQMZO6/NLcMBlm8AKyGhyMvaXuZQxxBJVIWJEAE5PtIwqo5PSsxOG+P53EmlZ9hsybn7JCy/CloEr+rw/sNRSvJPq/bBliRq9g4dfZ7UJqL81Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=ZXZeEAMO; arc=none smtp.client-ip=209.85.215.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ZXZeEAMO" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-c89956023dbso901022a12.0 for ; Wed, 01 Jul 2026 12:33:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1782934403; x=1783539203; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=4/M1D57lssm/A6RYRKDqaCs4EQpgkZGCf/uDo3WK1sI=; b=ZXZeEAMOXd+gHrL4Ktx3/Fo5Th6QRTtB4gXMfNdwTL+exRiPrqetCTfpZ98PhD9JV4 dM6KpfDSVh66P9265MUA1hTcgZ/qAmeUfmMXP3DuYgVYinTP0GKZop71+kmWbrdZemon hmt1oAEFd0goKUZF0XRjed/s2OFIxXj+duao0MGNFycUZpKnGRLLh0iEyMZkvAx15sMX ABvn0zFo5bN/L62mEHaRgff3vbIq0rZXTT8vqZu0SpEz0RJmWb9hmiAFMaWbBcghOHZA ebYcEAAVmEQ5cyBcm4eExiVeNAmyGQbD3q1ELWx3kSypvROtI5P5I6bggGB1joO5NW9I fIvQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782934403; x=1783539203; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=4/M1D57lssm/A6RYRKDqaCs4EQpgkZGCf/uDo3WK1sI=; b=okcckUYYLHvA/LxjvqZ6aBVEDoW06AhEsDYZkEY1cRyrHgCc8GXzgTKR3t8jdhseSr kxsMDxxVRyXelado2sVEf7WYezbMID+MkmgbIRe9WXZ2PZbtBTk8F+JvZcbY1bl7QcoH iPugfsMJt+a9TvCobZhY6pWR6mhaxEsaV4i8NhKfR5LK8QuTjk3SIqkU3wVeOKOYpPNz /VWUaMJCE7Srm/wUgjPYNBkhZfTLHyrQTcSt/ysrSE1dUtsioXeAjV4u9z8BhMmLcIhX 2Y2GPF5JYwBEK86rqZ8gzb1NnCKzwQQi80+Rnk552+26ud+ncCfCphKqYzKbmEMoUOhk 86Bw== X-Forwarded-Encrypted: i=1; AFNElJ8YTiEPn8nxujTKPewGzy5bx+hbMITpc71UMG4moju+cUuApynjE6mO7K5hXyayltwUgCMnlzUuvAM=@vger.kernel.org X-Gm-Message-State: AOJu0YzzlVycXbSondErMlra6DKDIuHeHcjPbYVHgIwwrxgbk8vtvHx3 If1f0zlrKEP+/eEWEc0YLIUVxJhtaShqzqFZTLnKMFaZpbmkoRAZlBtVGDJlncIr7YjT8j3HpYi tHAsWwQ== X-Received: from pgal188.prod.google.com ([2002:a63:3ec5:0:b0:c98:a4cf:469b]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a21:62cc:b0:3aa:c964:3c27 with SMTP id adf61e73a8af0-3bfed49ea64mr3435408637.46.1782934402561; Wed, 01 Jul 2026 12:33:22 -0700 (PDT) Reply-To: Sean Christopherson Date: Wed, 1 Jul 2026 12:32:07 -0700 In-Reply-To: <20260701193212.749551-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260701193212.749551-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.rc0.799.gd6f94ed593-goog Message-ID: <20260701193212.749551-47-seanjc@google.com> Subject: [PATCH v5 46/51] x86/paravirt: Plumb a return code into __paravirt_set_sched_clock() From: Sean Christopherson To: Jonathan Corbet , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Kiryl Shutsemau , Rick Edgecombe , Sean Christopherson , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Ajay Kaher , Alexey Makhalov , Jan Kiszka , Andy Lutomirski , Peter Zijlstra , Juergen Gross , Daniel Lezcano , John Stultz Cc: Shuah Khan , "H. Peter Anvin" , Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , linux-doc@vger.kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, xen-devel@lists.xenproject.org, Tom Lendacky , Nikunj A Dadhania , David Woodhouse , David Woodhouse , Michael Kelley , Thomas Gleixner Content-Type: text/plain; charset="UTF-8" Add a return code to __paravirt_set_sched_clock() so that the kernel can reject attempts to use a PV sched_clock without breaking the caller. E.g. when running as a CoCo VM with a secure TSC, using a PV clock is generally undesirable. Note, kvmclock is the only PV clock that does anything "extra" beyond simply registering itself as sched_clock, i.e. is the only caller that needs to check the new return value. Reviewed-by: David Woodhouse Signed-off-by: Sean Christopherson --- arch/x86/include/asm/timer.h | 6 +++--- arch/x86/kernel/kvmclock.c | 9 ++++++--- arch/x86/kernel/tsc.c | 5 +++-- 3 files changed, 12 insertions(+), 8 deletions(-) diff --git a/arch/x86/include/asm/timer.h b/arch/x86/include/asm/timer.h index 96ae7feac47c..ca5c95d48c03 100644 --- a/arch/x86/include/asm/timer.h +++ b/arch/x86/include/asm/timer.h @@ -14,14 +14,14 @@ extern int no_timer_check; extern bool using_native_sched_clock(void); #ifdef CONFIG_PARAVIRT -void __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable, - void (*save)(void), void (*restore)(void)); +int __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable, + void (*save)(void), void (*restore)(void)); static __always_inline void paravirt_set_sched_clock(u64 (*func)(void), void (*save)(void), void (*restore)(void)) { - __paravirt_set_sched_clock(func, true, save, restore); + (void)__paravirt_set_sched_clock(func, true, save, restore); } #endif diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 2cc3dd2ba355..22e8855fcd4d 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -332,10 +332,13 @@ static int kvmclock_setup_percpu(unsigned int cpu) static __init void kvm_sched_clock_init(bool stable) { + /* Ensure the offset is configured before making kvmclock visible! */ kvm_sched_clock_offset = kvm_clock_read(); - __paravirt_set_sched_clock(kvm_sched_clock_read, stable, - kvm_save_sched_clock_state, - kvm_restore_sched_clock_state); + + if (__paravirt_set_sched_clock(kvm_sched_clock_read, stable, + kvm_save_sched_clock_state, + kvm_restore_sched_clock_state)) + return; /* * The BSP's clock is managed via dedicated sched_clock save/restore diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 0f92b29adecc..012321fed5e5 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -280,8 +280,8 @@ bool using_native_sched_clock(void) return static_call_query(pv_sched_clock) == native_sched_clock; } -void __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable, - void (*save)(void), void (*restore)(void)) +int __init __paravirt_set_sched_clock(u64 (*func)(void), bool stable, + void (*save)(void), void (*restore)(void)) { if (!stable) clear_sched_clock_stable(); @@ -289,6 +289,7 @@ void __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; + return 0; } #else u64 sched_clock_noinstr(void) __attribute__((alias("native_sched_clock"))); -- 2.55.0.rc0.799.gd6f94ed593-goog