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[79.181.48.215]) by smtp.gmail.com with ESMTPSA id n7sm4780899qke.121.2019.12.15.01.54.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 15 Dec 2019 01:54:48 -0800 (PST) Date: Sun, 15 Dec 2019 04:54:42 -0500 From: "Michael S. Tsirkin" To: Peter Maydell Subject: Re: [PATCH 0/8] Simplify memory_region_add_subregion_overlap(..., priority=0) Message-ID: <20191215045230-mutt-send-email-mst@kernel.org> References: <20191214155614.19004-1-philmd@redhat.com> <31acb07b-a61b-1bc4-ee6e-faa511745a61@redhat.com> MIME-Version: 1.0 In-Reply-To: X-MC-Unique: fC3FQ3gePeGzeKQbDZMbPA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: No matching host in p0f cache. That's all we know. X-Received-From: 207.211.31.120 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: Paul Burton , Alistair Francis , Eduardo Habkost , kvm-devel , Marcelo Tosatti , QEMU Developers , Andrew Baumann , Alex Williamson , qemu-arm , Joel Stanley , Aleksandar Markovic , Paolo Bonzini , "Edgar E. Iglesias" , Aleksandar Rikalo , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Aurelien Jarno , Richard Henderson Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Sat, Dec 14, 2019 at 08:01:46PM +0000, Peter Maydell wrote: > On Sat, 14 Dec 2019 at 18:17, Philippe Mathieu-Daud=E9 wrote: > > Maybe we can a warning if priority=3D0, to force board designers to use > > explicit priority (explicit overlap). >=20 > Priority 0 is fine, it's just one of the possible positive and > negative values. I think what ideally we would complain about > is where we see an overlap and both the regions involved > have the same priority value, because in that case which > one the guest sees is implicitly dependent on (I think) which > order the subregions were added, which is fragile if we move > code around. I'm not sure how easy that is to test for or how > much of our existing code violates it, though. >=20 > thanks > -- PMM Problem is it's not uncommon for guests to create such configs, and then just never access them. So the thing to do would be to complain *on access*. --=20 MST