From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (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 6C6C0431E7C for ; Wed, 1 Jul 2026 21:47:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782942465; cv=none; b=KkO8ek98GFl+6R73GLWRblb/AlZfjt5ffHFzF+YnjFlG4KRwc0vpRGTGzVqEebm745A5yFBUXnroMw4b6gs5ThWgU+zrE7baQgqrxwxp416cnnFYPbbkQEcpitNx5JXnjkLQGfD5cuHd319BiJk4IfECJb8tsl2ov3iNRsKS438= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782942465; c=relaxed/simple; bh=s6Cr8zkyzrstP1cxKPxKWWNP4yvLxKRkyvcOWVE4+90=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=PDSUwS2ut3yEv3k5lyebIvvZRqEYqlqOgYqa4NCvaD5OHl39f7qAvzrAnRyDMD2lqA7XEjh6/tGn+sr+pkcz5/FdDrteI5dkuaXV0MsPLQPNSNXMGbxG9pNhDRwSmggNpOH+O3fG7pPzyye5sH0Q3xU9RCz2V+OiLmr1HaVVTiI= 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=rVpsp6AZ; arc=none smtp.client-ip=209.85.214.202 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="rVpsp6AZ" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-2c804e38c65so21351375ad.2 for ; Wed, 01 Jul 2026 14:47:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1782942463; x=1783547263; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=zcs7QN5Kd/BsLm+PUgFcojzf1bXkoGYIJwLkqkM7zHA=; b=rVpsp6AZSOy/NLznGTKp2Pw0DZ0B+eF94ddmhpHVgoxEcys5CrnXYKghzp3ABlufZF 1g5AedcwCOYpu8w4IjF2J9wDkww5bJFp6KEUHRuqyno36Noz4OAjLa8DUFJL8n/YdrqU a8VxfcQAbUtpiBel3y07+M6myY0PYPjLlRtpS8nLFQbkUYuL94DgIpp475jnWAjq+Wdh hUizv2HLC1hdwRwlSccQzYDddIQjKqlMWg17WvSQvPMQZhz3F5Pr6qdiD6wVTVYXpSk1 fOzpNm89My0UVP3OTI+55vYxTZqldejdJeDdcz8IT1pm2o6o1txbfhCvM9OzVmeDxkME bf/g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782942463; x=1783547263; h=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; bh=zcs7QN5Kd/BsLm+PUgFcojzf1bXkoGYIJwLkqkM7zHA=; b=PGU6YjQgWv+Jao3KIqlLAADNY21kVQ9YZ3czqXqV9z/+dhDHi1r1r8xr9DiqKZ489Q /IrZfFHocqWvjeFO8oV1FPzlhcf62Aa4Nr7Weh+rHu+JpJO5GjGqU+KocahN/yWspAUA A3nJjgr/Icp7orla2QGGPn/LUtUsIaJJKUmdw4bAPFXFZyasgVM+v/VxWdoDoIqSYnkA ugwi3sa3cRjRz3ibTqyVEt8ekUyLP5FBAcaZtIeEnkitWFW6uEnVRp6wGmqmcOSJBvxq AeyubQ5f/xq3ZaZsj7uWlEh67KO5jZnLsiaKemjueWgvezqY3mGr2AXg5vqlI82UgUT9 3Tlw== X-Forwarded-Encrypted: i=1; AHgh+RoKvltIqpOlkThlCITm13rlPVlt7Pjwgh5xmbnqLxD4WYzRgyMjT+COBHmR+QNBxHVbyUlzh0bOwps=@vger.kernel.org X-Gm-Message-State: AOJu0Yz0RW/QbOvozzmK36PnxzawXzhJ45jXJVZ6YOQHJqpy2/qt9GtW vM3W0V1V/2f1ZvHzuWLmjfsQvsqEixSQvwWk91w0IJeGs9av1fGbphIHBW90oeqM+uUs3c4GfrD 41VgYqQ== X-Received: from plzv3.prod.google.com ([2002:a17:902:b7c3:b0:2c8:7fe:29ac]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:32cc:b0:2c9:c083:cd49 with SMTP id d9443c01a7336-2ca7e69dfe3mr34635215ad.14.1782942462488; Wed, 01 Jul 2026 14:47:42 -0700 (PDT) Date: Wed, 1 Jul 2026 14:47:41 -0700 In-Reply-To: <20260608145455.89187-9-dwmw2@infradead.org> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260608145455.89187-1-dwmw2@infradead.org> <20260608145455.89187-9-dwmw2@infradead.org> Message-ID: Subject: Re: [PATCH v5 08/34] KVM: x86: Add KVM_VCPU_TSC_SCALE and fix the documentation on TSC migration From: Sean Christopherson To: David Woodhouse Cc: Paolo Bonzini , Jonathan Corbet , Shuah Khan , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Vitaly Kuznetsov , Juergen Gross , Boris Ostrovsky , Paul Durrant , Jonathan Cameron , Sascha Bischoff , Marc Zyngier , Joey Gouly , Jack Allister , Dongli Zhang , joe.jin@oracle.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, xen-devel@lists.xenproject.org, linux-kselftest@vger.kernel.org Content-Type: text/plain; charset="us-ascii" On Mon, Jun 08, 2026, David Woodhouse wrote: > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index c1897d939da9..6337f9b9d7ac 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -5930,6 +5930,9 @@ static int kvm_arch_tsc_has_attr(struct kvm_vcpu *vcpu, > case KVM_VCPU_TSC_OFFSET: > r = 0; > break; > + case KVM_VCPU_TSC_SCALE: > + r = kvm_caps.has_tsc_control ? 0 : -ENXIO; > + break; > default: > r = -ENXIO; > } > @@ -5950,6 +5953,22 @@ static int kvm_arch_tsc_get_attr(struct kvm_vcpu *vcpu, > break; > r = 0; > break; > + case KVM_VCPU_TSC_SCALE: { > + struct kvm_vcpu_tsc_scale scale; > + > + if (!kvm_caps.has_tsc_control) { > + r = -ENXIO; > + break; > + } Uber nit. For consistency with KVM's bizarre pattern here: r = -ENXIO; if (!kvm_caps.has_tsc_control) break; > + > + scale.tsc_ratio = vcpu->arch.l1_tsc_scaling_ratio; > + scale.tsc_frac_bits = kvm_caps.tsc_scaling_ratio_frac_bits; > + r = -EFAULT; > + if (copy_to_user(uaddr, &scale, sizeof(scale))) > + break; > + r = 0; > + break; > + } > default: > r = -ENXIO; > } > @@ -5989,6 +6008,9 @@ static int kvm_arch_tsc_set_attr(struct kvm_vcpu *vcpu, > r = 0; > break; > } > + case KVM_VCPU_TSC_SCALE: Another stupid consistency nit. Probably do this? /* * TSC scaling information is read-only (it's a reflection of * the TSC frequency, which can be set by userspace). */ r = kvm_caps.has_tsc_control ? -EINVAL : -ENXIO; > + r = -EINVAL; /* Read only */ > + break; > default: > r = -ENXIO; > }