From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f72.google.com (mail-pj1-f72.google.com [209.85.216.72]) (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 03FD53AB288 for ; Tue, 6 Oct 2026 13:12:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.72 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791292373; cv=none; b=NZLaZRAs6f+e46cAidbcOTbH8VavFjBDd9q4DcU8hiD93koLIB9YoUGSjm0BCEAcoEb/Q7in6UNsR97TiH30GuRfadeyw31rdkzTV8xMWPry5V8KG2VG1ukynh+QbvoBaPVnmXab35PENbgoBcw2ezHBoVQeKnRBskanxCsv1ik= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791292373; c=relaxed/simple; bh=843kLH3/yocor68fXyEXcidqAx3GXtqnd20UQZArqzw=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=O7RKQ6JUnzKdW9nU7qtp8Fk5ZoQojx5nS7kqiZnpvkx6JL7OyD4Y8pZLgXKEVuh2HTSBzMzPYFQ4X1DQ83qWq/pT0AMlZjDKSKEnGuqtwUwGOSdMaZbjhkbOvyVBW1vy0X0CAyO4L0IYjhstozJ6PpCAnp82H7NF4J7YzOQm34A= 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=KqK6UsZZ; arc=none smtp.client-ip=209.85.216.72 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="KqK6UsZZ" Received: by mail-pj1-f72.google.com with SMTP id 98e67ed59e1d1-3a7fa5e0442so2986047a91.0 for ; Tue, 06 Oct 2026 06:12:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1791292371; x=1791897171; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=26NSOuBm63PkzAzx+PKXKyXgL6+gizpi+djw/qIZoVs=; b=KqK6UsZZpeK3/wl6tTrfoQAztomHjfVcVmqB02SinD8k/7Ph3Z2cWXyFr6FHheXteX MIgUpQ7Ski4gmXQfeiOr5EthTE/rAR7v1WfGJo5oxDMHOtuBtx7iXtbRwibrJAfGQ1kL 49qG/xgKTJy/B+FK1V0AhFaGERCHrmwf9t68XyuT/JYveAuoTnA5Zw7YbEsO9qXF07zy AZ/5D3JXGBS98lj/4BOM8rBSNBezav6jPgLDCHSeia0xklBwgZtGLWWho1VyLmduJlIK w1Acv/NGyR4JJJYK7QYcWkIalqqj/Ol5jf1z/NkJjNJx6rDa8E+mzvmtWpreFT1Yy9Sk Q31A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791292371; x=1791897171; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=26NSOuBm63PkzAzx+PKXKyXgL6+gizpi+djw/qIZoVs=; b=GyCjrFiGYA+NQoBAKsWPxHqwW7gb6jdxa/ytO6CSLcjq6wkroFOYMlUrxUqjk77yCl kwC8UKZUbygADPfPP1UMo1mx7elWcIxtp5mzHzmUdtlo8Ao5OuqMiroCBtyrWSIrVLEH RGLw64veC83iJCGr3VVjPrAGkgNzgsExl6uCGBn8YCwsxBA14DZ6K/MttfFkWPqoo2dD L6Uq+n8emodkh1L20cK5vuEbdsX8MuTLzg4M4msgdqFueEo7XzIrRYclhzmG/bkZbiq4 9Jq4X0rqojieDSH+5I2eu47OOBlJ9ZwSn8vPu2R+DdF+0A6ma1EvUpKCnvwqLAgSbQrq MsRw== X-Gm-Message-State: AFq9FYJ1gW0PydZrU+WQs2j6kfE/IUb0twfjuE8yL4ie1R4id/pS9qtw GlvKgXHgid1MNRZHPSG9Wv7geTSJLjwCmzIcRPkgraCTkI/30KvdXQETHwxJ7SBxf/riNm+HJui hX9EWBA== X-Received: from pgbcv14.prod.google.com ([2002:a05:6a02:420e:b0:cca:9486:8b0b]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:4a8f:b0:3a0:9640:803a with SMTP id 98e67ed59e1d1-3a872ae690dmr1095191a91.5.1791292371055; Tue, 06 Oct 2026 06:12:51 -0700 (PDT) Date: Tue, 6 Oct 2026 06:12:39 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: Message-ID: Subject: Re: [RFC/DISCUSSION] x86/tsc: Handling legacy PIT fallback calibration on modern platforms From: Sean Christopherson To: Matthias Hahn Cc: "linux-kernel@vger.kernel.org" , "x86@kernel.org" , "tglx@linutronix.de" , "mingo@redhat.com" , "bp@alien8.de" , "dave.hansen@linux.intel.com" , "peterz@infradead.org" Content-Type: text/plain; charset="us-ascii" On Tue, Oct 06, 2026, Matthias Hahn wrote: > (sorry, resending as plain text) > > Hi everyone, > > We have recently observed an issue regarding TSC calibration fallback on > modern client/server platforms (specifically Raptor Lake and newer) when > running inside restricted virtualized environments. Can you give this Linux-as-a-guest TSC cleanup series a spin? Among other things, it addresses the problem of a constant, stable TSC being marked unstable because the thing being used to calibrate the TSC is itself unstable. https://lore.kernel.org/all/20260806233609.212337-1-seanjc@google.com