From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f71.google.com (mail-pj1-f71.google.com [209.85.216.71]) (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 449593D75AD for ; Fri, 31 Jul 2026 23:16:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.71 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785539774; cv=none; b=eK7wsxTuT6+X7Gv0y7U66lDdVj7vFSE5Eeq1gfy6LYGkPkjWy53cSDhNw5Xwufd4KIa6bveP4eXzR1gjrks/YcceCTRp2mpYRZy2+nCh/0KlH0VNNpuodJ/hrFeWYy3+421AXplGnoGjiCXdTtVbIIrL36z+l/YUBq4bmoBYqKk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785539774; c=relaxed/simple; bh=A2ZszD5oB/5IQjIY93Gpv4YTCK5z3C0SzJKpHpheYqk=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=q4B5P9awo/Hbnw+fyoTr+BnkHw+ELECbH1ryslavBGvdjKZoHFM1OSfKmU0Io/SI8x0fd3aUs/Ir5AVmyhHseHffGRfPXPfofioBN2WrsGJj3C19iX9CUUoQOB2C/KCuKicml2Bx7xPwqw5D1ahaGXfuB8/g53RSXzj130z+qbA= 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=A8OuXPAN; arc=none smtp.client-ip=209.85.216.71 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="A8OuXPAN" Received: by mail-pj1-f71.google.com with SMTP id 98e67ed59e1d1-38ecc48b3c2so2330985a91.1 for ; Fri, 31 Jul 2026 16:16:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1785539773; x=1786144573; darn=vger.kernel.org; h=content-transfer-encoding:content-type:cc:to:from:subject :message-id:references:mime-version:in-reply-to:date:from:to:cc :subject:date:message-id:reply-to:content-type; bh=A2ZszD5oB/5IQjIY93Gpv4YTCK5z3C0SzJKpHpheYqk=; b=A8OuXPANnLkDjarhzKPe24I6SF43B15rvif1t1SQ0QC67vSCeuD6AXVGy/D3nWeQNH Pav0kVzw0SgEy1O6C6cpRR7MXAUl4tz2Quzdj8/Un9nv4U27NsyY2Ly5RZbgBJM25zWT uOd0UGXyFkUXkVj+Fs24OSsNHhGtSIr8B0EFeo8CBFPW2M4EsQLoLlPsntwau+rxy0rv hWAEEF3RVWKmW+41MAQlwEGylETmDUiRym/EHVy/kwogCZFjncvpZ8pdClWKVMGbpFDF p3b+cddI/bBOLzuiReaGe+Q+I5EWk/HZT6uUxA4aEICIRh0aHVE18tHma2p7n0bHZDAu vV4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785539773; x=1786144573; h=content-transfer-encoding:content-type: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 :content-type; bh=A2ZszD5oB/5IQjIY93Gpv4YTCK5z3C0SzJKpHpheYqk=; b=NVnf3iJdRjPnxnn7kJhmJclHDtbl4qlfWRhQtCS2fenG0Aqx1HMxqoiKhOUAtIrh9f pdoalHgwjk9VTClxwHldFs3BsOoQO1iupYgPneHfY5D7wLUP7qyCUmYGzB1XsNowax25 vXjJ+llBgSK9uWG80xBru0cfzDdeFn3O35KVSm2vhtw4L7gG+AZWf8argtnrs9fO0OuF iPMrOuPlYlGLcy6uGikKBAS7tK8iLJlzR7kqqK5L1q1FrC1FfTQcWpR5lcFOI2wryII2 MUoQ48R0EiG1dv323umMKy8uSNPhWaW7ZvP6kviRkh9guVr4T5weEBXX6jltlo1cOyKM 1b7A== X-Forwarded-Encrypted: i=1; AHgh+Rr7OcwD2pBUWTkVw1pADEjNPCaCQnr1mcXieN/VOyzwI719MWGlS0YZtqxt/cb8T2i6bFDFUNvYCDM=@vger.kernel.org X-Gm-Message-State: AOJu0Yw4b2/+SRrBNQmOvL2FuE0AoXE1FLqBGgG5KUTWzxTrXV1UrHpm zhttquxeDrYp8avV4pM+j57Owd1CEnoJttXges5MES/xRKEKFk1FTYDmeX6PqXlJjGO3cExv1H1 lsmxxTg== X-Received: from pjbqx12.prod.google.com ([2002:a17:90b:3e4c:b0:38e:a577:5cbd]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:584e:b0:38e:76f8:fcbe with SMTP id 98e67ed59e1d1-38fbc561b48mr1327142a91.29.1785539772383; Fri, 31 Jul 2026 16:16:12 -0700 (PDT) Date: Fri, 31 Jul 2026 16:16:11 -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: <20260703212145.343527-1-dwmw2@infradead.org> <20260703212145.343527-6-dwmw2@infradead.org> Message-ID: Subject: Re: [PATCH v6 05/36] KVM: x86: Add KVM_[GS]ET_CLOCK_GUEST for accurate KVM clock 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="utf-8" Content-Transfer-Encoding: quoted-printable On Sat, Jul 25, 2026, David Woodhouse wrote: > On Fri, 2026-07-24 at 14:17 -0700, Sean Christopherson wrote: > > On Fri, Jul 03, 2026, David Woodhouse wrote: > > > +4.145 KVM_GET_CLOCK_GUEST > > > +---------------------------- > > > + > > > +:Capability: none > >=20 > > Why not add a CAP?=C2=A0 The check in the subsequent selftest is quite = gross. >=20 > Because nobody would ever use it in practice anyway.=20 Yes, the selftest will. > Even if the ioctl is present, you *still* have to try it and fall back to= the > old method because there are ways that a *guest* can force master clock m= ode > off. That's totally fine, but userspace, especially for selftests, needs a way t= o know the ioctl exists and _should_ work.