From: Thomas Gleixner <tglx@linutronix.de>
To: Sean Christopherson <seanjc@google.com>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Juergen Gross <jgross@suse.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
Ajay Kaher <ajay.kaher@broadcom.com>,
Jan Kiszka <jan.kiszka@siemens.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
John Stultz <jstultz@google.com>
Cc: linux-kernel@vger.kernel.org, linux-coco@lists.linux.dev,
kvm@vger.kernel.org, virtualization@lists.linux.dev,
linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org,
Tom Lendacky <thomas.lendacky@amd.com>,
Nikunj A Dadhania <nikunj@amd.com>
Subject: Re: [PATCH v2 24/38] timekeeping: Resume clocksources before reading persistent clock
Date: Thu, 27 Feb 2025 08:48:53 +0100 [thread overview]
Message-ID: <87r03jeska.ffs@tglx> (raw)
In-Reply-To: <20250227021855.3257188-25-seanjc@google.com>
On Wed, Feb 26 2025 at 18:18, Sean Christopherson wrote:
> When resuming timekeeping after suspend, restore clocksources prior to
> reading the persistent clock. Paravirt clocks, e.g. kvmclock, tie the
> validity of a PV persistent clock to a clocksource, i.e. reading the PV
> persistent clock will return garbage if the underlying PV clocksource
> hasn't been enabled. The flaw has gone unnoticed because kvmclock is a
> mess and uses its own suspend/resume hooks instead of the clocksource
> suspend/resume hooks, which happens to work by sheer dumb luck (the
> kvmclock resume hook runs before timekeeping_resume()).
>
> Note, there is no evidence that any clocksource supported by the kernel
> depends on a persistent clock.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
next prev parent reply other threads:[~2025-02-27 7:49 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-02-27 2:18 [PATCH v2 00/38] x86: Try to wrangle PV clocks vs. TSC Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 01/38] x86/tsc: Add a standalone helpers for getting TSC info from CPUID.0x15 Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 02/38] x86/tsc: Add standalone helper for getting CPU frequency from CPUID Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 03/38] x86/tsc: Add helper to register CPU and TSC freq calibration routines Sean Christopherson
2025-03-04 4:17 ` Michael Kelley
2025-02-27 2:18 ` [PATCH v2 04/38] x86/sev: Mark TSC as reliable when configuring Secure TSC Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 05/38] x86/sev: Move check for SNP Secure TSC support to tsc_early_init() Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 06/38] x86/tdx: Override PV calibration routines with CPUID-based calibration Sean Christopherson
2025-02-27 13:15 ` Kirill A. Shutemov
2025-02-27 2:18 ` [PATCH v2 07/38] x86/acrn: Mark TSC frequency as known when using ACRN for calibration Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 08/38] clocksource: hyper-v: Register sched_clock save/restore iff it's necessary Sean Christopherson
2025-03-04 4:17 ` Michael Kelley
2025-03-04 17:39 ` Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 09/38] clocksource: hyper-v: Drop wrappers to sched_clock save/restore helpers Sean Christopherson
2025-03-04 4:17 ` Michael Kelley
2025-02-27 2:18 ` [PATCH v2 10/38] clocksource: hyper-v: Don't save/restore TSC offset when using HV sched_clock Sean Christopherson
2025-03-04 4:17 ` Michael Kelley
2025-02-27 2:18 ` [PATCH v2 11/38] x86/kvmclock: Setup kvmclock for secondary CPUs iff CONFIG_SMP=y Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 12/38] x86/kvm: Don't disable kvmclock on BSP in syscore_suspend() Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 13/38] x86/paravirt: Move handling of unstable PV clocks into paravirt_set_sched_clock() Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 14/38] x86/kvmclock: Move sched_clock save/restore helpers up in kvmclock.c Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 15/38] x86/xen/time: Nullify x86_platform's sched_clock save/restore hooks Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 16/38] x86/vmware: Nullify save/restore hooks when using VMware's sched_clock Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 17/38] x86/tsc: WARN if TSC sched_clock save/restore used with PV sched_clock Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 18/38] x86/paravirt: Pass sched_clock save/restore helpers during registration Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 19/38] x86/kvmclock: Move kvm_sched_clock_init() down in kvmclock.c Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 20/38] x86/xen/time: Mark xen_setup_vsyscall_time_info() as __init Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 21/38] x86/pvclock: Mark setup helpers and related various as __init/__ro_after_init Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 22/38] x86/pvclock: WARN if pvclock's valid_flags are overwritten Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 23/38] x86/kvmclock: Refactor handling of PVCLOCK_TSC_STABLE_BIT during kvmclock_init() Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 24/38] timekeeping: Resume clocksources before reading persistent clock Sean Christopherson
2025-02-27 7:48 ` Thomas Gleixner [this message]
2025-02-27 2:18 ` [PATCH v2 25/38] x86/kvmclock: Hook clocksource.suspend/resume when kvmclock isn't sched_clock Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 26/38] x86/kvmclock: WARN if wall clock is read while kvmclock is suspended Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 27/38] x86/kvmclock: Enable kvmclock on APs during onlining if kvmclock isn't sched_clock Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 28/38] x86/paravirt: Mark __paravirt_set_sched_clock() as __init Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 29/38] x86/paravirt: Plumb a return code into __paravirt_set_sched_clock() Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 30/38] x86/paravirt: Don't use a PV sched_clock in CoCo guests with trusted TSC Sean Christopherson
2025-02-27 13:17 ` Kirill A. Shutemov
2025-02-27 2:18 ` [PATCH v2 31/38] x86/tsc: Pass KNOWN_FREQ and RELIABLE as params to registration Sean Christopherson
2025-03-04 4:18 ` Michael Kelley
2025-02-27 2:18 ` [PATCH v2 32/38] x86/tsc: Rejects attempts to override TSC calibration with lesser routine Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 33/38] x86/kvmclock: Mark TSC as reliable when it's constant and nonstop Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 34/38] x86/kvmclock: Get CPU base frequency from CPUID when it's available Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 35/38] x86/kvmclock: Get TSC frequency from CPUID when its available Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 36/38] x86/kvmclock: Stuff local APIC bus period when core crystal freq comes from CPUID Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 37/38] x86/kvmclock: Use TSC for sched_clock if it's constant and non-stop Sean Christopherson
2025-02-27 2:18 ` [PATCH v2 38/38] x86/paravirt: kvmclock: Setup kvmclock early iff it's sched_clock Sean Christopherson
2025-02-28 11:23 ` [PATCH v2 00/38] x86: Try to wrangle PV clocks vs. TSC David Woodhouse
2025-03-03 20:53 ` Sean Christopherson
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