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 023EF343898; Wed, 20 May 2026 19:05:09 +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=1779303911; cv=none; b=eoVh+NWvSR2ZJ0uhWXtzNwN8W5OinVvY168hlH6CTiFGfTQyyJPuIC9PAUW5xOKh+v9fYSrMjV4dGspbOCxJ4Bu5akPub1Y8bJI/7BNFIFQ3chPTOAMRegwsp4bBF5AhIS9sotWIZavdT0YjqPB6ALytiHmEuANsylp19hkE3Eo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779303911; c=relaxed/simple; bh=F/Fpt6jTcy4NSrTkND1yYtGMnDHF82o6TRRAxJt0yGU=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=nUWxG+FpjoTGXK9U+Jb4dwvSzHEY9fXEMxmsIwi7jJPq8rbEvPCo9TCq0D/aaugkAN4VYWzweVXk8gyv6++3BY2wNKR7he2BV+MpMsC5+0eDYT2cKbKPfr+5Omw1WpqCs7o4kFQqXZdD8F5GXf2fOBsjwfmTqToiYR6B2tD8VNI= 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=rAm9IlUy; 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="rAm9IlUy" 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=8tbHSXv0PduRga+zT/mB8RJeehigf48DptUBou4PkPA=; b=rAm9IlUyk+WfmPm0L70sobS35Q 8cq3fq5zSk3bgOImc18izqE3hqDuQBOcWwAi1O5HYkWy3804x5Hjt615HyGyxul4NFnCjSsO5DuzO 0Wxma947xFddm4dHrcR64NJpJnhW0sHTZj6QA8BkmxeP1xHky+iq9cKJEUdVkrGyoMG9YFRydPnR6 YlGcmhd8pc1HNqDjRNgjymByHXAfA4JYQeQ8Gf/vYwygDzLtt8HiAlvIKUc0Ka10cd3IR029AM3DB kB6a2OPg+Fry3XggO/NRKqNmPNLOj7ncCeZNbT9L1Prz6s1Oiz7PpN3BRBJUUYLlxc3EzNGKIzJIi 0csYMZKQ==; 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 1wPmE0-00000007Uvp-12En; Wed, 20 May 2026 19:05:00 +0000 Message-ID: <44e0d60548d317fd59895f18bd17220dfb2f834b.camel@infradead.org> Subject: Re: [PATCH v3 02/41] x86/tsc: Add helper to register CPU and TSC freq calibration routines 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: Wed, 20 May 2026 20:04:58 +0100 In-Reply-To: <20260515191942.1892718-3-seanjc@google.com> References: <20260515191942.1892718-1-seanjc@google.com> <20260515191942.1892718-3-seanjc@google.com> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-BQ4J6FeuOLTRewu0k3H0" User-Agent: Evolution 3.52.3-0ubuntu1.1 Precedence: bulk X-Mailing-List: linux-hyperv@vger.kernel.org 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 --=-BQ4J6FeuOLTRewu0k3H0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2026-05-15 at 12:19 -0700, Sean Christopherson wrote: > Add a helper to register non-native, i.e. PV and CoCo, CPU and TSC > frequency calibration routines.=C2=A0 This will allow consolidating handl= ing > of common TSC properties that are forced by hypervisor (PV routines), > and will also allow adding sanity checks to guard against overriding a > TSC calibration routine with a routine that is less robust/trusted. >=20 > Make the CPU calibration routine optional, as Xen (very sanely) doesn't > assume the CPU runs as the same frequency as the TSC. >=20 > Wrap the helper in an #ifdef to document that the kernel overrides > the native routines when running as a VM, and to guard against unwanted > usage.=C2=A0 Add a TODO to call out that AMD_MEM_ENCRYPT is a mess and do= esn't > depend on HYPERVISOR_GUEST because it gates both guest and host code. >=20 > No functional change intended. >=20 > Reviewed-by: Michael Kelley > Tested-by: Michael Kelley > Signed-off-by: Sean Christopherson Mildly concerned that we might want to support multiple options =E2=80=94 d= oes it have CPUID 0x15? Does it have 0x40000x10? Does it have a pvclock? There are various permutations of those which are perhaps best handled by *trying* each one, in some order, and populating a struct with the answers? But on the basis that perfect is the enemy of good, Reviewed-by: David Woodhouse > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > index b5991d53fc0e..e9e7394140dd 100644 > --- a/arch/x86/kernel/kvmclock.c > +++ b/arch/x86/kernel/kvmclock.c > @@ -321,8 +321,8 @@ void __init kvmclock_init(void) > =C2=A0 flags =3D pvclock_read_flags(&hv_clock_boot[0].pvti); > =C2=A0 kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT); > =C2=A0 > - x86_platform.calibrate_tsc =3D kvm_get_tsc_khz; > - x86_platform.calibrate_cpu =3D kvm_get_tsc_khz; > + tsc_register_calibration_routines(kvm_get_tsc_khz, kvm_get_tsc_khz); > + > =C2=A0 x86_platform.get_wallclock =3D kvm_get_wallclock; > =C2=A0 x86_platform.set_wallclock =3D kvm_set_wallclock; > =C2=A0#ifdef CONFIG_X86_LOCAL_APIC Can we move those (and maybe everything in the context there too) up *before* the check for no-kvmclock at the top of the function? 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