From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A7DC22DC76C; Wed, 20 May 2026 23:50:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779321052; cv=none; b=MhbwM3eLDzO1otC/0MGsUIATfZnSrqKVwOlkyXVP+uOE1xDXC7VckOd3UzWZngyYJgUhYRXt9MBH7E7+xl/7xeUhOPus3o3B1NTLwWgfexs5L6LjyLKXf9foUD7Xom5qkPXPmFtr3xszztS9crM+tlzsTSUqc2BD+zhlDlcD6XA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779321052; c=relaxed/simple; bh=kjXkTST37i+1gmjQGjhQW588QxcAxvvLMWHi+QpQkZo=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=SuA68lwWA52FWNHLWo9cMzWbSYbZ9t3w4XWg8apb6cbKpOcRuUZir1fltERtEZml/3eQKRN7h1mZMGeTprZuEBTqnrDiFwl1OFlCfTw+PXFsQnljSvrsFQXrVHkm/yu3erZZhNOKkUAideTJNzLbPkm23SBzbCCOSlLzS9oXnk4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=casper.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=a5PC97TD; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=casper.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="a5PC97TD" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=MIME-Version:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=kjXkTST37i+1gmjQGjhQW588QxcAxvvLMWHi+QpQkZo=; b=a5PC97TD9BKkPl+3e0F6kGlkZ9 zCbTS/Oo+FoXd4urkvEM1VR8kscN/rFTBlB5Z0VoUPn/tgTVyzLP3mx8Kqx/lgHAjvRXZ5fGmkApq jHycwdxF4CqRMaL9mzfuhEvvxFdjD2nnfR9DrD7M3cNRzkUyVcKrDzywFPGi/JDGD933yYoqOAdBU deLaoIWGnTDPJb9+jlSQbH9XgV4bfbQ4hfKlIgngYj5XFzOZEjja6vzFMmUl0jpACj4GQlvZ4GMG+ pNTKyQDM8Bxl7QRUXdZGXFvtIno1U6YAorOg7bqfzc1CJA4JWbFiBWIRS9XHfXE8x4tA/8O/7XQa+ 2P8z9lXA==; Received: from 54-240-197-227.amazon.com ([54.240.197.227] helo=freeip.amazon.com) by casper.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wPqgS-00000007lNX-069X; Wed, 20 May 2026 23:50:40 +0000 Message-ID: <1e46bbafd280fa70137e530e6694e969f305ab11.camel@infradead.org> Subject: Re: [PATCH v3 32/41] x86/tsc: Rejects attempts to override TSC calibration with lesser routine From: David Woodhouse To: Sean Christopherson , Kiryl Shutsemau , 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 Cc: Rick Edgecombe , Vitaly Kuznetsov , Broadcom internal kernel review list , Boris Ostrovsky , Stephen Boyd , 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 , Thomas Gleixner Date: Thu, 21 May 2026 00:50:38 +0100 In-Reply-To: <20260515191942.1892718-33-seanjc@google.com> References: <20260515191942.1892718-1-seanjc@google.com> <20260515191942.1892718-33-seanjc@google.com> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-a1hInw8KTqMYkOpxFKcW" User-Agent: Evolution 3.52.3-0ubuntu1.1 Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org. See http://www.infradead.org/rpr.html --=-a1hInw8KTqMYkOpxFKcW Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2026-05-15 at 12:19 -0700, Sean Christopherson wrote: > When registering a TSC frequency calibration routine, sanity check that > the incoming routine is as robust as the outgoing routine, and reject the > incoming routine if the sanity check fails. >=20 > Because native calibration routines only mark the TSC frequency as known > and reliable when they actually run, the effective progression of > capabilities is: None (native) =3D> Known and maybe Reliable (PV) =3D> > Known and Reliable (CoCo).=C2=A0 Violating that progression for a PV over= ride > is relatively benign, but messing up the progression when CoCo is > involved is more problematic, as it likely means a trusted source of > information (hardware/firmware) is being discarded in favor of a less > trusted source (hypervisor). >=20 > Signed-off-by: Sean Christopherson 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