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Fri, 13 Nov 2020 14:24:54 +0100 (CET) From: Markus Armbruster To: "Dr. David Alan Gilbert" Subject: Re: [PATCH 2/6] migration: Fix migrate-set-parameters argument validation References: <20201113065236.2644169-1-armbru@redhat.com> <20201113065236.2644169-3-armbru@redhat.com> <20201113114926.GF3251@work-vm> Date: Fri, 13 Nov 2020 14:24:54 +0100 In-Reply-To: <20201113114926.GF3251@work-vm> (David Alan Gilbert's message of "Fri, 13 Nov 2020 11:49:26 +0000") Message-ID: <87tuttfkyh.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=216.205.24.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/12 08:00:44 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, 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=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no 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: qemu-devel@nongnu.org, quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" "Dr. David Alan Gilbert" writes: > * Markus Armbruster (armbru@redhat.com) wrote: >> Commit 741d4086c8 "migration: Use proper types in json" (v2.12.0) >> switched MigrationParameters to narrower integer types, and removed >> the simplified qmp_migrate_set_parameters()'s argument checking >> accordingly. >> >> Good idea, except qmp_migrate_set_parameters() takes >> MigrateSetParameters, not MigrationParameters. Its job is updating >> migrate_get_current()->parameters (which *is* of type >> MigrationParameters) according to its argument. The integers now get >> truncated silently. Reproducer: >> >> ---> {'execute': 'query-migrate-parameters'} >> <--- {"return": {[...] "compress-threads": 8, [...]}} >> ---> {"execute": "migrate-set-parameters", "arguments": {"compress-threads": 257}} >> <--- {"return": {}} >> ---> {'execute': 'query-migrate-parameters'} >> <--- {"return": {[...] "compress-threads": 1, [...]}} >> >> Fix by resynchronizing MigrateSetParameters with MigrationParameters. > > Having those two separate types is a pain! It is! MigrateSetParameters is the argument of migrate-set-parameters, MigrationParameters is the result of query-migrate-parameters and part of the internal migration state. Differences: (1) Optional members For migrate-set-parameters, we need *all* members to be optional. For migration state and query-migrate-parameters, we want only some members to be optional (currently only @tls-authz, I think). (2) Special values migrate-set-parameters has a "reset to default, whatever that may be" feature for some members (currently only @tls-creds, @tls-hostname, @tls-authz, I think). Doing that cleanly requires an additonal value. The first attempt to fuse the two types (commit de63ab6124 "migrate: Share common MigrationParameters struct", 2016-10-13) took care of (1). Introspection of query-migrate-parameters became mildly misleading (it claims members are optional that aren't), and C code dealing with migration state had to take care to set the has_FOO = true. Tolerable. I had to revert it to address (2) cleanly and in time: commit 01fa559826 "migration: Use JSON null instead of "" to reset parameter to default", 2017-07-24. A second try needs to take care of (2) as well. Messes up query-migrate-parameters some more: introspection claims a few members can be null that can't. Is the "reset" feature is worth all that trouble? Is overloading migrate-set-parameters a good idea? >> Fixes: 741d4086c856320807a2575389d7c0505578270b >> Signed-off-by: Markus Armbruster > > Reviewed-by: Dr. David Alan Gilbert Thanks!