From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f53.google.com (mail-pj1-f53.google.com [209.85.216.53]) (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 F37F043B6D7 for ; Wed, 5 Aug 2026 11:50:47 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.53 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785930650; cv=none; b=AMHwpG6xRDfIq65Km5YXNR2m51mZhJQVTIsJ0mKzzyvs+Xei+izy1tJpt88GlqsN1wF+aCb4kTicCZqucw+3qPpdu+MAHo6/S1Cjipv8YIRvkyFj7jzJCQ1EFIMuu9u9sPur0jBbya4PWBak/e2y5ApVlNJAAvkC5XHrlXpxKA0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785930650; c=relaxed/simple; bh=8pB7ceD77AuYDPuNy5sp4YIR/n6BG/LvwP4jI0nxD+I=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=GdX4f4Vs43HKuWK2JsMF/5qt6I28D2kd/EKeJ5vxpZwIaeyEna9nlOgnmu8aoQT+i1FZl8EuaB3EAHkBXlZuBHH1OUz6VH8fFAqx8Wf5Gzq0bSEUmhbtgUoQ8CshlNfx3KSSyGmYsK+oz9D7AnEAjtD3qIdBG5E/CLorzr5WbmY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=Id9ZbJPT; arc=none smtp.client-ip=209.85.216.53 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Id9ZbJPT" Received: by mail-pj1-f53.google.com with SMTP id 98e67ed59e1d1-3856d6fbcb3so669941a91.2 for ; Wed, 05 Aug 2026 04:50:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1785930647; x=1786535447; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to:content-type; bh=9VOjG1qeqbpED3aclWfN9lJ5XhH5+1/8WZV2to/loYI=; b=Id9ZbJPTCWTxJejmJ8zF26h8rAq9Hsz19pmsfrNKNk4MZPtixmPIubQ/HfbUMlYlwj Qrd5Je9sc9u3jwj+Oqb30RXV6Q12LC38VgFAB5uRyZuvhMVHt7DQvLnMDuUphPgOQT+f LMEdn/cPWhDhStvUtWqHEy9f3VBh2wlPKuIMf74HguZsoBdQP/dwTXV9eBV5oqXYcsdO sG+UhEhNDnveXWJSEzMZV7xyYolyzt8SoTUaDCZAL+ugSua9Tpxcl78JXZ60/Xkct78/ 0UbP/+xtql/e2/y5ovXjvIPMPKq6rUD+ypyWUndAgmQ7wyJ+tXMn39mr3GTDTPUS6hMr ZpSQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1785930647; x=1786535447; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-gg:x-gm-message-state:from :to:cc:subject:date:message-id:reply-to:content-type; bh=9VOjG1qeqbpED3aclWfN9lJ5XhH5+1/8WZV2to/loYI=; b=aRr4GWWIaI1SKrGYwy3hgKkc8iNLSvS4NJf1pRllM3yB9HaLGY3JXXvLSspQrzcvur ttuCyJuQfdDbOq/15gO6MugNGifemaQSVJzHHv4L2XC7QYIocsobZk+A6e9QdK9IgR3Q GHsMq238QxhwrQDqOezxn13ZCAISQsLq+XBsx7IsyCPFei9ZLeyWwPJY4eivJ7Hxb6BA AJM6bEAs3o/FOpTjP4IXrFHiCt/vIrqZduZhUnOQEuPRcmGVUc1vbYtZp6gXmc1PzaOh MAtjoZuVDpbm3Tmss//e+EGgA/hiqdPHYenV0nx39bb/Jc69URC8bft98Xzw/IPJueWM y2Hg== X-Forwarded-Encrypted: i=1; AHgh+RrLH7vteKy7Btx6tPQo3NLM69XDbeX44SYjVeN/Ew2IPdeCcMkiNJ/zcu3RybsoVzQbpurgzZTQWBpFx+0=@vger.kernel.org X-Gm-Message-State: AOJu0Yyh6lBG4FBa8uEVpOk98YeEfidzNDvv24Kevr9CMLjyP+exs0pX OgYlKAi0kjtTmTVPkrtMyfzSDY7QlSldmtFOoVb5vaoKjnWkZZoI4SjI X-Gm-Gg: AR+sD12BU2IaFxWPc0PM2PHXxyaeLLSvY3XR6ejDKuc+XtM5NRNlORMu9EN78/3PiQm gD8TNkt2vW8ewClWa5dSL6SRGlsVaURHJYA+LH5S6zblRlpHR25st6LZ4IGv0KYGHG2y1303XXA 3REUdjEadHU9pjWugRibGfgZ2GcdZKFDxQsuQc/UhDLsmdi6Eou3zIdgKE0kLl7T5DypISN47UX rF06wn/nu0bW0srs/Bq9SdUopbuFrAK2IpEVil0BeAEJaTM6a7voPP+6Mm4Nb8hz91FBRb7Y2nt sPZfMZ6q6IQRXh0U/CyawZnHdwt+rLyUsyQSPXyzCx6C8BULeSKP9SmcnaGiwPgfie4awgj4kDi pamS0RCOrlFW12U7wBHuOowtEyt4+dAelmwLvJtTvR+x9zT3mVGCma/dhM8bm2XELG+vtbg1y+a CYzIaPab6Y09JGVto5C6LgoiJ89IYgMrgSeqo3pAj5L70Ndqo85SpdqpWskzgYrF+eTHHz8c61T QQUK4x8xEYZl7QbP+deow/zwBOoLTk3A72pYx9reQYbK0rTeaaC8Hi6MlXXUgxqqrw1jCBS4jRh jTKpiuc6xdWW9fQLsI0kwDIlolU3Ax4LSzrQoSGmhLR/GC6jB/+b X-Received: by 2002:a17:90b:224e:b0:38e:9ef9:eb97 with SMTP id 98e67ed59e1d1-3903c5c443dmr5103146a91.16.1785930647103; Wed, 05 Aug 2026 04:50:47 -0700 (PDT) Received: from spider.bream-herring.ts.net ([103.252.203.158]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3903927db6esm2936674a91.10.2026.08.05.04.50.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 05 Aug 2026 04:50:46 -0700 (PDT) From: Matthias Goergens To: Roger Pau Monne Cc: Matthias Goergens , Juergen Gross , Roger Pau Monne , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Yannick Martin , Thorsten Leemhuis , Stefano Stabellini , Oleksandr Tyshchenko Subject: Re: [PATCH v2] x86/xen: fix init of balloon stats again Date: Wed, 5 Aug 2026 19:50:41 +0800 Message-ID: <20260805115041.409008-1-matthias.goergens@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260805094008.95778-1-roger@xenproject.org> References: <20260730143548.39320-1-roger@xenproject.org> <20260805094008.95778-1-roger@xenproject.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Roger, v2 looks good to me. Keying append on the source of the initial count covers every case I can construct: by inspection, a domU always enters the fallback branch (current_pages stays 0), so HVM/PVH domU and the dom0 hypercall-failure path share the subtraction branch, while the PV start_info path and a successful dom0 XENMEM_current_reservation append. I also ran it on a nested-KVM Xen rig (Xen 4.23-unstable, Linux 11028ab62899e as dom0, static busybox initramfs): - PV dom0, dom0_mem=2048M,max:4096M and 3072M,max:4096M, CONFIG_XEN_UNPOPULATED_ALLOC=n: no WARN, current_kb matches dom0_mem (2 and 3 GiB respectively). Same with =y. - PVH dom0, same two memory configurations, =n: v1 WARNed in balloon_init and returned -ERANGE in exactly these cases; v2 completes cleanly and the balloon driver initialises. (Scope note: PVH dom0 userspace stalls later in boot under nested KVM for an unrelated reason, so the PVH evidence is boot-time dmesg and the balloon sysfs state.) Tested-by: Matthias Goergens Thanks, Matthias