From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f199.google.com (mail-pl1-f199.google.com [209.85.214.199]) (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 E3E0C566C7B for ; Thu, 10 Sep 2026 17:59:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.199 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789063159; cv=none; b=KxDqHj558yxSgI0uVpfLGZjxkITV43CAzHs/cm9oGbw3r5UBHCnmcxGaUS6Ya7SBwvgNYX9UCgReF8X0UbN83BySgwNPV3i/n9sFBalrR50M9w/dH/d8XK256/KXq47N8D0oT6ZINja2TEl5WFtBh+hYVpQt5ZoJpw4RJZeRpIE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789063159; c=relaxed/simple; bh=iihdVpeTD7xqvFs81N5pzrr3yHNO8lXqn++m5NS1tpY=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Content-Type; b=GS9aPbE9EbFZy6leO0dyYlqdcwPCiErS9YGm8nBbgz9oAAnXRQzuIoLWW1x3Asi2WIVsgN6MLXP5ElcniXKVdoDEJKIKov9kP74vjAhu+hCsExFTUyi1exhooWeyJwtY+qu3S4X2Cz/Rd2iGGzyP9OO67x1JPgjfKcJCT0WuDLQ= 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=Qp0PeyC1; arc=none smtp.client-ip=209.85.214.199 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="Qp0PeyC1" Received: by mail-pl1-f199.google.com with SMTP id d9443c01a7336-2d6fb956002so107265605ad.1 for ; Thu, 10 Sep 2026 10:59:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1789063157; x=1789667957; darn=vger.kernel.org; h=content-type:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=VdUk7xT6Q2S0XYOIdYUuypvFM5moeaGi7+AJeTxN8N4=; b=Qp0PeyC1s/TlCYvWFn3xsZc47//NfWkIAzttYA+mbNnTss7pmMXJpRYv4tU+ObTZN+ x680/ndDKtd4iof2E5/Npt/XrEqItRPArY0pUeRjKh5RvXjdCqn0ssDE9bCrX9UFjShk DpNQ+mSlH+FyvQKJYI9+11ES0TOChqQk3jfmF93W8v5rk77jOoDfdiq8uN91LZgjOE2B dOMDDM9j3So7ee/tFy9tEIRtpd/YOEokwpbVSIWJqvedhbsZLD1DkkuKNcPS/vdiVGdj c9l/hiXm+Z6gTnufOs+N9ybQmPtk0sCF9wEOpWNaSu/khgVuVxJwMn+MooE2lbgxZG0K 4yXg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1789063157; x=1789667957; h=content-type: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=VdUk7xT6Q2S0XYOIdYUuypvFM5moeaGi7+AJeTxN8N4=; b=C3tF9eQvI+wZ1FpjKM71CZX75xzo9Ppx23gF4ucOXVi2PS9iVGaF86t/m3WiNGBLfi SOMQ1hD2qiLAYu59CcCmAtv6hYcZ36aS/b4MM3Swdz7NLXgBWKPjZOv28wMmDMSrWHtn ym/Yq9j7A4I6pppaG9FT9Z63VCvnm7ooAZW1UVyB1JozmI5zJzwljULA/YMNUQvTKPXv gnC6SZukc+UYhuh6Hh6N90CGRF+Utjui4eGASRGFLE7j7aQUD0DwJYArAfVX+nav6hko 8znWor4Ac0s8yMUfkLe+IJ4NUQzPTQxkjxHhsW8QiuXgzR7HUG6BX6Q1mac5wB4kPKdR akLw== X-Forwarded-Encrypted: i=1; AKwUvBxad/J7vhpxLLbHomabpcVGkKuH5zZtbDcqN6wS7YpFG6U0E6Dm2nKHKHsjXL7CA98GZin2GK4f7bjc0Bg=@vger.kernel.org X-Gm-Message-State: AFuF++ln0GcdU7zC0mAhM4KhdCuGeh7jGjsHH+lQ+OMrSbXLG19PWZ56 2UrULxU4HHa/iKvZJ+kMkVq2x9tiE9gsRBn77FzL4h5tZNppIKb5Dy/l5G2/aibEiZWsx+F7N2W 6a4N/KA== X-Received: from pleg13.prod.google.com ([2002:a17:902:e38d:b0:2c9:b703:3bfb]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:ce8b:b0:2d7:2edd:d140 with SMTP id d9443c01a7336-2dd2a1c3e42mr9017035ad.3.1789063156725; Thu, 10 Sep 2026 10:59:16 -0700 (PDT) Date: Thu, 10 Sep 2026 10:59:16 -0700 In-Reply-To: <20260806233609.212337-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260806233609.212337-1-seanjc@google.com> Message-ID: Subject: Re: [PATCH v6 00/51] x86: Try to wrangle PV clocks vs. TSC From: Sean Christopherson To: Kiryl Shutsemau , Rick Edgecombe , Paolo Bonzini , "K. Y. Srinivasan" , Haiyang Zhang , Wei Liu , Dexuan Cui , Long Li , Ajay Kaher , Alexey Makhalov , Jan Kiszka , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Juergen Gross , Daniel Lezcano , Thomas Gleixner , John Stultz , Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , Miroslav Lichvar , x86@kernel.org, linux-coco@lists.linux.dev, kvm@vger.kernel.org, linux-hyperv@vger.kernel.org, virtualization@lists.linux.dev, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, Michael Kelley , Tom Lendacky , Nikunj A Dadhania , David Woodhouse , David Woodhouse , Thomas Gleixner Content-Type: text/plain; charset="us-ascii" On Thu, Aug 06, 2026, Sean Christopherson wrote: > The primary goal of this series to fix flaws with SNP and TDX guests where a > PV clock provided by the untrusted hypervisor is used instead of the secure > TSC that is controlled by trusted firmware. > > The secondary goal is modernize running under KVM. Currently, KVM guests will > use TSC for clocksource, but not sched_clock. And Linux-as-a-KVM-guest doesn't > support paravirt enumeration of the TSC/APIC frequencies, even though QEMU > provides that information by default. > > The tertiary goal is to clean up the PV clock code to deduplicate logic across > hypervisors, and to hopefully make it all easier to maintain going forward. > > The quaternary goal is to clean up the TSC calibration code, which was made > stupidly hard to follow by hypervisor code mixing in with the native > calibration routines, instead of being implemented as a pure alternative. > > Note, the VMware and Xen changes still probably should get acks from those > maintainers, as my understanding of what they're trying to do may be flawed. This (thankfully) still applies cleanly. What can I do to help move this forward?