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Mon, 15 Jun 2020 09:40:19 +0000 (UTC) Date: Mon, 15 Jun 2020 10:40:16 +0100 From: "Dr. David Alan Gilbert" To: Markus Armbruster Subject: Re: [PATCH v2] hmp: Make json format optional for qom-set Message-ID: <20200615094016.GC2883@work-vm> References: <20200610075153.33892-1-david@redhat.com> <87pna0c0pr.fsf@dusky.pond.sub.org> MIME-Version: 1.0 In-Reply-To: <87pna0c0pr.fsf@dusky.pond.sub.org> User-Agent: Mutt/1.14.0 (2020-05-02) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=207.211.31.81; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/06/15 01:43:27 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action 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: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Eduardo Habkost , David Hildenbrand , qemu-devel@nongnu.org, Paolo Bonzini , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Markus Armbruster (armbru@redhat.com) wrote: > David Hildenbrand writes: > > > Commit 7d2ef6dcc1cf ("hmp: Simplify qom-set") switched to the json > > parser, making it possible to specify complex types. However, with this > > change it is no longer possible to specify proper sizes (e.g., 2G, 128M), > > turning the interface harder to use for properties that consume sizes. > > > > Let's switch back to the previous handling and allow to specify passing > > json via the "-j" parameter. > > Two issues: > > 1. Makes qom-get and qom-set inconsistent > > qom-get formats as JSON, always. > > qom-set parses the string visitor's undocumented ad hoc language by > default. You can make it parse JSON by passing -j. > > Not a show stopper, but sure ugly. I feel documentation should point > it out. I can imagine one way around this owuld be to remove the flag and make it happen in the failure case; i.e.: obj = qobject_from_json(value, &err); if (err == NULL) { qmp_qom_set(path, property, obj, &err); } else { somehow check if it parses with the integer parser and if it does use object_property_parse } unfortunately that else path is a bit messy, because you need to pick a parser in this case and then if that fails probably present the json error message not it's error. > 2. Rearms the string visitor death trap > > If you try to qom-set a property whose ->set() uses something the > string input visitor doesn't support, QEMU crashes. I'm not aware of > such a ->set(), but this is a death trap all the same. Mind, I > didn't actually *look* for such a ->set(). Details: > > Subject: Re: [RFC PATCH] qom: Implement qom-get HMP command > Date: Sat, 02 May 2020 08:02:43 +0200 (6 weeks, 2 days, 4 minutes ago) > Message-ID: <87a72q6fi4.fsf@dusky.pond.sub.org> > https://lists.nongnu.org/archive/html/qemu-devel/2020-05/msg00178.html > > Since we've had this death trap in the code for a number of years, I > can't call its restoration a show stopper. It does feel like an > unadvisable risk, though. That just needs fixing in qom somewhere; it shouldn't assert - people are too free with asserts. Dave -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK