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Thu, 12 Sep 2019 05:42:26 -0700 (PDT) Received: from [192.168.10.150] ([93.56.166.5]) by smtp.gmail.com with ESMTPSA id q25sm7627498wmq.27.2019.09.12.05.42.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 12 Sep 2019 05:42:26 -0700 (PDT) To: Wei Yang References: <20190321082555.21118-1-richardw.yang@linux.intel.com> <20190321082555.21118-3-richardw.yang@linux.intel.com> <20190823010750.GA21179@richard> <20190912025150.GA25169@richard> From: Paolo Bonzini Openpgp: preference=signencrypt Message-ID: Date: Thu, 12 Sep 2019 14:42:26 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190912025150.GA25169@richard> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH 2/6] exec.c: remove an unnecessary assert on PHYS_MAP_NODE_NIL in phys_map_node_alloc() X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: rth@twiddle.net, qemu-devel@nongnu.org, mst@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/09/19 04:51, Wei Yang wrote: > On Fri, Aug 23, 2019 at 09:07:50AM +0800, Wei Yang wrote: >> On Thu, Aug 22, 2019 at 12:24:32PM +0200, Paolo Bonzini wrote: >>> On 21/03/19 09:25, Wei Yang wrote: >>>> PHYS_MAP_NODE_NIL is assigned to PhysPageEntry.ptr in case this is not a >>>> leaf entry, while map->nodes_nb range in [0, nodes_nb_alloc). >>>> >>>> Seems we are asserting on two different things, just remove it. >>> >>> The assertion checks that this "if" is not entered incorrectly: >>> >>> if (lp->skip && lp->ptr == PHYS_MAP_NODE_NIL) { >>> lp->ptr = phys_map_node_alloc(map, level == 0); >>> } >>> >> >> Hmm... I may not get your point. >> >> phys_map_node_alloc() will get an available PhysPageEntry and return its >> index, which will be assigned to its parent's ptr. >> >> The "if" checks on the parent's ptr, while the assertion asserts the index for >> the new child. I may miss something? >> > > Hi, Paolo, > > Do I miss something? Sorry, I was on vacation. phys_page_set_level can be called multiple times, with the same lp. The assertion checks that only the first call will reach phys_map_node_alloc. Paolo