From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (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 11C7D382294 for ; Fri, 22 May 2026 12:49:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779454193; cv=none; b=MaYIxWiwDMBbYZKTKqkbXvSvZh7HoSrij5SgT0ZuNQa5UQXsp/CeFFcJM3rgxSXqZQ/EfZnaH9+2KcfG7yBx7ND4lBT45hBvb7RvNJ7RBXLND+xfO02Pzs/tjD7Q6ARVxN3kLR142qt6FKxJREmxnr/5Q1mi8uzEDclcwA/TlNI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779454193; c=relaxed/simple; bh=RbHOtVV6OeY+ZEk+4bAtnYf6cI1SHn8hUw08eOY8EZM=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Q9gWG2GEebT3+9PmC5TKJNUkZ4cIlLxfX3Tt8TudpBr6JPdJImH6ZOv0vw0BAx1yLuso+3IBoLhk7uFadVnXGTuNUcDaSyWJ4Pj7MeXz0JYRjGIEpW36jbxUsIh291gUoWw0RKRyIT4PaDedfgfcXviCodVFZaasOYVlWmHKUiQ= 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=czYTJFew; arc=none smtp.client-ip=209.85.214.201 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="czYTJFew" Received: by mail-pl1-f201.google.com with SMTP id d9443c01a7336-2b9a3c3c4eeso72137975ad.3 for ; Fri, 22 May 2026 05:49:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1779454191; x=1780058991; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=DQXBtYOgD26OY0sxOaH3yIHE1h+TPqKS3BQiU+AvFJA=; b=czYTJFewNgQdudNdgwZ55E1+qPLX/eGbyT9zSr6Vfh27zIYrh5JeIpUkdT4qKbIJAn SCQfKHCc79A2ralZCRnqE7xqd/+WAkYl9RpZulbZ+8OWnhpXZXJjAT/6MOb+3nygBqCY /yXMpXT0iQ4TwXVvqcqgyW8SJsw3esyWj2mbVO16EIX1fNci1PWWE6w2nTxY2oSJPKNH uigKHszq9m4nhoT5+6B9imaZ6HHu+PEOpPb+/5774Bti5CH+EdiEvn7TOEnafnnOK4I8 9uMj+980rBC2uvn5pgF7QSBmfXmeQFqOZYjETtuhWevuB7i0Zafn+fxtJYH8ixEXlLHB soYA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1779454191; x=1780058991; h=content-transfer-encoding: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=DQXBtYOgD26OY0sxOaH3yIHE1h+TPqKS3BQiU+AvFJA=; b=RaohOjqfb3EGXo2dGt0oWL7orM7LovgkhzgzxbUJfP92v8aEs+95z+J1DLYVYfhekn DrAkZ8Hb+TnQywjHv0/QXmngcVpiuyoZrlkzfFLxY5HknMuGRu0XsewFyU0U7ijAcDCX Ewn7HxByzIwI9xo7M/he0xe5yTQlsPmKOgVg6gkaR1c4ZgWoMs6uA4Wf3F6W7/Uc/Qvx hoDELWZWKbgIcIA7oqgrkMphvY8UYdaP+93a31l7rVa11V3WOMH2YAivZgHMhU8TpDCM gqh1mKV9LWPamAe1ZIy+gMFL06fcqXmHpbQmqAD1cvdhx+a5PBAYeThFOJslUlTG5C3D vslQ== X-Forwarded-Encrypted: i=1; AFNElJ9zyr+MVGyH2sgtQ3L8HYhHBGw0vwHOSWcMfouG1u0l/TSgdYiSBeHf9Uml7wc9kNPNl5LSQeqaK9o=@vger.kernel.org X-Gm-Message-State: AOJu0YxFCVvbYXnOsYz6LC73gXz3SAS7urNresOzEF5QQw5mNgA6VsbD omepm/GNo73pTtzscIXlOotY4BJ2k0m2KNpFAzLXIDYicMyQlTZ16R56ZFw6k5rRFysCRQaK2w/ OflM66w== X-Received: from plpf11.prod.google.com ([2002:a17:903:3c4b:b0:2b0:51f0:272d]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:c94d:b0:2b4:63bf:5535 with SMTP id d9443c01a7336-2beb073d568mr36887635ad.41.1779454190670; Fri, 22 May 2026 05:49:50 -0700 (PDT) Date: Fri, 22 May 2026 05:49:50 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260509224824.3264567-1-dwmw2@infradead.org> <20260509224824.3264567-28-dwmw2@infradead.org> <3ad6cd109480772ade3c11f23b9c1d7a9855d67e.camel@infradead.org> Message-ID: Subject: Re: [PATCH v4 27/30] KVM: x86: Add KVM_VCPU_TSC_EFFECTIVE_FREQ attribute 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="utf-8" Content-Transfer-Encoding: quoted-printable On Thu, May 21, 2026, David Woodhouse wrote: > On Thu, 2026-05-21 at 15:30 -0700, Sean Christopherson wrote: > > On Thu, May 21, 2026, David Woodhouse wrote: > > > On Sat, 2026-05-09 at 23:46 +0100, David Woodhouse wrote: > > > > From: David Woodhouse > > > That does leave userspace still needing a way to get the APIC bus > > > frequency, to populate CPUID. So maybe I'll just make an attribute > > > which returns that as a single value. > >=20 > > Already exists, KVM_CAP_X86_APIC_BUS_CYCLES_NS.=C2=A0 The TDX architect= ure decided > > that unconditionally telling guests the virtual APIC bus runs at 400Mhz= was a > > brilliant idea. >=20 > Ah, thanks. >=20 > So KVM always exposes 1GHz by default regardless of the actual host? > Which is why there's no *get* method? >=20 > (Well... getting KVM_CAP_APIC_BUS_CYCLES_NS returns > APIC_BUS_CYCLE_NS_DEFAULT which is 1, so it's basically just returning > 1 like a lot of cap queries do, and *not* returning what the period is > actually set to) Oh, that's just an oversight, definitely not intentional. Easy enough to f= ix: diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 1616b2eec6e7..cd4a244ca0c5 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2235,7 +2235,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, lon= g ext) r =3D tdp_enabled; break; case KVM_CAP_X86_APIC_BUS_CYCLES_NS: - r =3D APIC_BUS_CYCLE_NS_DEFAULT; + r =3D kvm ? kvm->arch.apic_bus_cycle_ns : APIC_BUS_CYCLE_NS= _DEFAULT; break; case KVM_CAP_EXIT_HYPERCALL: r =3D KVM_EXIT_HYPERCALL_VALID_MASK;