From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f73.google.com (mail-pj1-f73.google.com [209.85.216.73]) (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 1F37F22173A for ; Mon, 21 Jul 2025 22:26:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753136770; cv=none; b=fbJfpIa4m8qjLGVyqCriTJVBqe7CmbbLgEMVJqWyNi6NkCm30f6p287BPC6hqfVggK8tUl4hE+TtCxEjnWbwuS0FRYXg/XGHyYN6p8ARv9CLEZ2wmfrL8Ckf4TbnS/LDwlGTIAUCeJgENFpLtdrkBqZMOtz2TQM746YVjz9EbgY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1753136770; c=relaxed/simple; bh=IyvP8QHlTa2QpWvqlFYR9SEvyFxbF/ATcjcrXYbVJ2I=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=qTsLXStQQ7FdFsoVFftXSLyEFFvIdkhBRF555xAvn8zQtdzGaJ238pTgQ38HRrYdNvCT4FMOds2JUbNYIUP5Fakdwp3RWdr2YuJKp478YBvtvlHKZcwYDDG6u7PbQz55LXvxuri3FlBzWuMrrXVrArNvsE48fGWWmgCOV/Avfw0= 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=Cmt1uubr; arc=none smtp.client-ip=209.85.216.73 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="Cmt1uubr" Received: by mail-pj1-f73.google.com with SMTP id 98e67ed59e1d1-31e3fdf1906so108190a91.0 for ; Mon, 21 Jul 2025 15:26:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1753136768; x=1753741568; 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=LL2cGKuHaaPjxufWOQkCjzE9tdmYpzd1lzvFg8IW6fY=; b=Cmt1uubrOI27eeR6IElR2/K8H5Ao8oLkbwmkpeqXg0yb/32x9R8xWovsN7eo4mtTLE 4zSlf7BIESO3R3eOiyQrwraWES4zD2vS515QGrwV20KsZuxjB13ywDIxjnsRLGooapmj mfGBHdRmtA7WcLk/YsvZuFfqKqbpdItENgw6YQuuznM2/rRYL+qR9TSfUSsjd/3E83TC Ue3/Ui4A+rbt+2k8fS2EypynZhKNTOKfTSJBJCG1IcFDV8+zIzZcy4zL8c3+8fVrV4lj dOOR35+2o4sq7jEC1Gh2eLRt3t9SlmMgB5oy+Or09UtKW1OUiY608+dUk7Yu7jO2TXP0 biDw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1753136768; x=1753741568; 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=LL2cGKuHaaPjxufWOQkCjzE9tdmYpzd1lzvFg8IW6fY=; b=f6iQZexZtqb7XzkLgoX4e7v0bhvRlHOQhx0jHA0wq5kSUZvzLlRv5FqGIxwxGjUO1l 77I17Wi1KxElPVbkVMpoCvc3Zs7oaxQJThXJzjPm9qDesrLjdDXVPsNhszpX0+VZoAnY eCkKirST+fEkOGU1rIY0sUwufERDKcAuipRNXp1hDk/IGky05pYO6o0tkS1LsaJhB8Qq I/dRqd0aNCicjne8Of3FY5P4JtZV5QFKlmtw1/BP+2Gya0TdAICFTMIrDDtTuDj0pV9v ZOZWYUsYxx7Km1L8VKWdJu7SBLTjbWEA3qobRP7x3ySRIhoUomT+qvx1vkYl70LCPLok dbDQ== X-Forwarded-Encrypted: i=1; AJvYcCWNwCcUnqP1GMeRUa+KcpOp0VG5cXcILmfhgTseSE6x7NFr4DeaRnMIy/UhCJWfHkL342529u/jcUN7L+o=@vger.kernel.org X-Gm-Message-State: AOJu0Yzgq4Mw1kwG0ZnACz/cOSmO/vJgGj/Z3hw83uicmFvb1dh3xEmC kkveefDV+7bKiIX0d2GVSzF0+C2y82uudSdmv4PqHkXD3SBlXpwuBdW9VW0c847cfdgamWCqe0n bpOSmPw== X-Google-Smtp-Source: AGHT+IFOEfi1TplIejvNZRr/1MbPEFH8m6+GDazbtftWiE+uc1xJ4NSswHFa4ynpaZqg1Tm3n/YWoEjzkPQ= X-Received: from pjwx13.prod.google.com ([2002:a17:90a:c2cd:b0:313:230:89ed]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:50ce:b0:313:5d2f:54fc with SMTP id 98e67ed59e1d1-31cc25429b9mr22489997a91.10.1753136768428; Mon, 21 Jul 2025 15:26:08 -0700 (PDT) Date: Mon, 21 Jul 2025 15:26:07 -0700 In-Reply-To: <7t5qpdpc7cvkyvgj7i2fes56pvpfvrqcpbbdqqrhu3vgqgtjw2@6mpuc4ljmiey> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <330d10700c1172982bcb7947a37c0351f7b50958.1740036492.git.naveen@kernel.org> <6dl4vsf3k7qhx2aunc5vdhvtxpnwqp45lilpdsp4jksxtgdu6t@kubfenz4bdey> <7t5qpdpc7cvkyvgj7i2fes56pvpfvrqcpbbdqqrhu3vgqgtjw2@6mpuc4ljmiey> Message-ID: Subject: Re: [PATCH v3 1/2] KVM: SVM: Increase X2AVIC limit to 4096 vcpus From: Sean Christopherson To: Naveen N Rao Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Paolo Bonzini , Suravee Suthikulpanit , Vasant Hegde Content-Type: text/plain; charset="us-ascii" On Mon, Jul 21, 2025, Naveen N Rao wrote: > On Fri, Jul 18, 2025 at 07:24:15AM -0700, Sean Christopherson wrote: > > If there wasn't already an "x2AVIC enabled" print, I would probably lean toward > > doing nothing. But since pr_info("x2AVIC enabled\n") already exists, and has > > plently of free space for adding extra information, there's basically zero downside > > to printing out the number of supported CPUs. And it's not just a binary yes/no, > > e.g. I would wager most people couldn't state the number of vCPUs supported by > > the "old" x2AVIC. > > Ok, this is what I have now. Let me know if you prefer different > wording: > > /* AVIC is a prerequisite for x2AVIC. */ > x2avic_enabled = boot_cpu_has(X86_FEATURE_X2AVIC); > - if (x2avic_enabled) > - pr_info("x2AVIC enabled\n"); > + if (x2avic_enabled) { > + if (cpu_feature_enabled(X86_FEATURE_X2AVIC_EXT)) > + x2avic_max_physical_id = X2AVIC_4K_MAX_PHYSICAL_ID; I actually like the approach you initially posted, where KVM explicitly sets x2avic_max_physical_id for both paths. KVM could obviously rely on global initialization to set X2AVIC_MAX_PHYSICAL_ID, but it's not like this code is performance critical, and have all paths in one place makes it easy to understand what the "default" value is. if (cpu_feature_enabled(X86_FEATURE_X2AVIC_EXT)) x2avic_max_physical_id = X2AVIC_MAX_PHYSICAL_ID_4K; else x2avic_max_physical_id = X2AVIC_MAX_PHYSICAL_ID; > + pr_info("x2AVIC enabled (upto %lld vCPUs)\n", x2avic_max_physical_id + 1); Maybe s/upto/max? > + } > > > - Naveen