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 1E6E72773CB; Thu, 4 Sep 2025 12:15:15 +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=1756988119; cv=none; b=fvXAyw5Hg9oJGmuVlxBBpO6gzWAi0Q2Ss9pv0U2+1+Okqb6aQPMVCmMSq6roSyn0eajKkEgW5VEKrYHFB3WrlDGShv8lE4fIZECbiI8+ckD0Ijes9UGmFIVuSXRnPZiIJECxdiDunGtkR0BPLBHuSS00Og0xyH31sSwbvvhfysk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756988119; c=relaxed/simple; bh=/CTICnVOF+pKcVUO21pD4vYnwXyys1BxAg/9iooDLuM=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=EyqqNBN8WEMlftMQAzsRfrvqNX2JPH3Woso5wSW910eqfwBm7bYQ7pB0Ttu9JMi7CpVrrfB5l6XP2IvbwOGh6i8oX7/sjD5+JH/RrnMsT+csEoHbZh5Sqqpff4WHmiC6IMw3K7wjKzc6e9M0Tuw6XhjDZCM4JzFWEo9ATOntkQs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (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=APTqI9mi; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (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="APTqI9mi" 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=/CTICnVOF+pKcVUO21pD4vYnwXyys1BxAg/9iooDLuM=; b=APTqI9miTZkiLuvz616GQ4ZPdw XojlEu5k5r2NssLD+kdei3UweBMEqLjMI/S0rhWp0AlgTGbDHLNCusB9it6E3VmuhOKGEXLhbz6iM CuMAznVrUSxJ5ziUu2Oghn62QHX3DSx4YlAq/7wTIj0BHYgIQQ5daP53XvuN0H8IrpkgpiEO/J0io SF3R2pGSOzMPVy0Mq3rWDOaLd4coRsf0qOTDXC6q8VhcGdeNPykpDY4Hocvr18F9Gn0/6YcVidQX+ L9HisEUSkuueG7cEmcViV2SAAVYl6OXhPCMfarcr2qSZMplk5n+a3J0C9BOqFzUflmLI37UHMT+Bp BQcHSLXg==; Received: from [54.239.6.190] (helo=freeip.amazon.com) by casper.infradead.org with esmtpsa (Exim 4.98.2 #2 (Red Hat Linux)) id 1uu8rk-00000000Zv4-2kZT; Thu, 04 Sep 2025 12:15:01 +0000 Message-ID: <4a3be390fe559de0bd5c61d24853d88f96a6ab6a.camel@infradead.org> Subject: Re: [PATCH v2 0/3] Support "generic" CPUID timing leaf as KVM guest and host From: David Woodhouse To: Sean Christopherson Cc: Paul Durrant , Fred Griffoul , Colin Percival , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "x86@kernel.org" , "H. Peter Anvin" , Vitaly Kuznetsov , "kvm@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Graf (AWS), Alexander" , Ajay Kaher , Alexey Makhalov Date: Thu, 04 Sep 2025 14:14:57 +0200 In-Reply-To: References: <54BCC060-1C9B-4BE4-8057-0161E816A9A3@amazon.co.uk> <3268e953e14004d1786bf07c76ae52d98d0f8259.camel@infradead.org> Content-Type: multipart/signed; micalg="sha-256"; protocol="application/pkcs7-signature"; boundary="=-/jSEI9CyeXnZghyoPmYb" User-Agent: Evolution 3.52.3-0ubuntu1 Precedence: bulk X-Mailing-List: kvm@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 --=-/jSEI9CyeXnZghyoPmYb Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2025-09-04 at 04:59 -0700, Sean Christopherson wrote: >=20 > I thought the original problem being solved was that the _guest_ doesn't = know the > effective TSC frequency?=C2=A0 Userspace can already get the effectively = TSC frequency > via KVM_GET_TSC_KHZ, why do we need another uAPI to provide that?=C2=A0 (= Honest question, > I feel like I'm missing something) I believe that KVM_GET_TSC_KHZ returns what userspace *asked* for the TSC frequency to be (vcpu->arch.virtual_tsc_khz), not what it actually ended up being based on the measured host frequency and the available scaling granularity (vcpu->hw_tsc_khz). --=-/jSEI9CyeXnZghyoPmYb Content-Type: application/pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 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