From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (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 BF0A9274FDF for ; Wed, 4 Feb 2026 14:21:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770214910; cv=none; b=bPeNbD1RFv2tfUniXa0+9sSlyGa+ZJ/ZWyie+M+M9IAGEW7X1PKggrf0AAj3GzgbuTW8Y5PMu52j3KTgFwpX+OnB66B3Ha2cMGUa5I/D1+gZVRdnfaP501KRe44AuND2YDf4Km6l9CFAcTBsqSVC4QxDGRP6Zls6TndpvVUlvBo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770214910; c=relaxed/simple; bh=0MNDA2Ny0tJNWAJdXkje5Nlf+llWLY+vVIb/GMcUhbc=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=MabqIcjTVji20ZTYW/ToNg2Yo4UdnK1z9zWVUF5aNTUR8EKPYzjWbkYqDrqQS7Mi1Xea2dxht73kXs6P0Shg2RC1wFFOT1LE6Zuoye2REDS5Vz2ylS1KduoqHYtOsCLAcMd2ENbhYc2TiuZEnbDa1cZ0BhxZdvf+gHLqyA1DAlw= 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=xFBfSsep; arc=none smtp.client-ip=209.85.216.74 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="xFBfSsep" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-34e70e2e363so1169241a91.1 for ; Wed, 04 Feb 2026 06:21:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1770214910; x=1770819710; 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=qVJvtKJuuvGxGxyWpMoMpOxiQua226/Cb1xLlw715Yg=; b=xFBfSsepGo6+crUBO/KeDDXyjoFOaMaOfK7qRqcv3HRkuvk1dyJyvZli6oAb7jnzIX Evn76/lYtNsiVad1vouAa5XHbWAFg6Z0MftAP/9gQKHdE2Sy/De3DAzYYo2cZARPrK+7 nbBhTN3c1G/9iF6dyPL2ksPFoS713weKk3fCCva6kyNLuuJib60IBu/MIwC7lSW+By26 HHeJSgX/ZmLFpXznxMjlPRECfkpfS3RUvjoevfqkFYGACNhrjiIPugtFu0mui5GzRfb7 c3BISO38gZnlqV+dcbhQv+82fWLUuIyn9vbO9rAIw0t2OcxiVmxaiLHcCA1toC+1YxhQ QF2g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1770214910; x=1770819710; 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=qVJvtKJuuvGxGxyWpMoMpOxiQua226/Cb1xLlw715Yg=; b=fwdRZyBGx9i2QSR3yeYcDcTmx+hj68/24zKz0Edt7j6/ZfrQOHpfc737/FzxcyLk2c 7sTEDaPLvoD3YhgKDFzSQCmjy2DlC1XSHpz8ICQ2RfcFGLw56QwOh7zWtqcv9HJw3ogi v44ExbUQbHrsIZG7bQf6mSdTiEXH20v8ogjTTtwtBi0U4HJVSTVwvC3Pv0Mmy7cnEpwP K6OvtCtfgMNG6SxNI5zBCxg1e+u3oKmm4RnNcTQNnRy+2wTGYyf6VgozTQi2b9Og36ss lMjEkOIK+iZmCXv/20YGGt3Ny2gUR9RPoYqq7poJPOK+tx1hD/y+jaAKv/2bASONaDtq sEDA== X-Gm-Message-State: AOJu0YyNFbVZUwKzJcPHDc+QRkYxwTbA6iH94OfsOxDVG5WwMmDi9vhP E+FAHFXZ0U5InalB1i2vZDzwbXpOIxN13DmgIGSPznBz8993cHd7TMSTpUKJAb5IZl1/2TJqiA9 GPDQggQ== X-Received: from pjbnk22.prod.google.com ([2002:a17:90b:1956:b0:34c:cb46:dad7]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:3d12:b0:34c:4c6d:ad0f with SMTP id 98e67ed59e1d1-3548721e9d2mr2606038a91.37.1770214909813; Wed, 04 Feb 2026 06:21:49 -0800 (PST) Date: Wed, 4 Feb 2026 06:21:48 -0800 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <7acdd9974effabe5dc461aa755eacf9fb0697467.1770116601.git.isaku.yamahata@intel.com> Message-ID: Subject: Re: [kvm-unit-tests PATCH] x86: apic, vmexit: replace nop with serialize to wait for deadline timer From: Sean Christopherson To: Isaku Yamahata Cc: kvm@vger.kernel.org, isaku.yamahata@gmail.com, Paolo Bonzini , isaku.yamahata@linux.intel.com Content-Type: text/plain; charset="us-ascii" On Tue, Feb 03, 2026, Isaku Yamahata wrote: > On Tue, Feb 03, 2026 at 10:30:06AM -0800, > Sean Christopherson wrote: > > > > +static inline void serialize(void) > > > +{ > > > + /* serialize instruction. It needs binutils >= 2.35. */ > > > > And a CPU that supports it... I don't see any point in using SERIALIZE. To check > > for support, this code would need to do CPUID to query X86_FEATURE_SERIALIZE, and > > CPUID itself is serializing (the big reason to favor SERIALIZE over CPUID is to > > avoid a VM-Exit for performance reasons). > > Thank you for pointing it out. I'll replace it with raw_cpuid(0, 0). > Or do you want to opencode cpuid() in each places? It probably makes sense to add a helper to arm the deadline timer, and deal with the serialization there. E.g. start_tsc_deadline_timer() also has a nop() of dubious value.