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Szmigiero" , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Subject: Re: [PATCH v6 18/19] migration/multifd: Stop changing the packet on recv side In-Reply-To: References: <20240827174606.10352-1-farosas@suse.de> <20240827174606.10352-19-farosas@suse.de> Date: Tue, 27 Aug 2024 15:45:11 -0300 Message-ID: <87plptx0so.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Queue-Id: 1D3F01FB81 X-Spamd-Result: default: False [-4.51 / 50.00]; BAYES_HAM(-3.00)[99.99%]; NEURAL_HAM_LONG(-1.00)[-1.000]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; MISSING_XM_UA(0.00)[]; RECEIVED_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:106:10:150:64:167:received]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_ALL(0.00)[]; FUZZY_BLOCKED(0.00)[rspamd.com]; RCPT_COUNT_THREE(0.00)[4]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns,suse.de:dkim,suse.de:mid]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:2; envelope-from=farosas@suse.de; helo=smtp-out2.suse.de 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, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Peter Xu writes: > On Tue, Aug 27, 2024 at 02:46:05PM -0300, Fabiano Rosas wrote: >> @@ -254,12 +250,10 @@ int multifd_ram_unfill_packet(MultiFDRecvParams *p, Error **errp) >> return 0; >> } >> >> - /* make sure that ramblock is 0 terminated */ >> - packet->ramblock[255] = 0; >> - p->block = qemu_ram_block_by_name(packet->ramblock); >> + ramblock_name = g_strndup(packet->ramblock, 255); > > I understand we want to move to a const*, however this introduces a 256B > allocation per multifd packet, which we definitely want to avoid.. I wonder > whether that's worthwhile just to make it const. :-( > > I don't worry too much on the const* and vars pointed being abused / > updated when without it - the packet struct is pretty much limited only to > be referenced in this unfill function, and then we will do the load based > on MultiFDRecvParams* later anyway. So personally I'd rather lose the > const* v.s. one allocation. > > Or we could also sanity check byte 255 to be '\0' (which, AFAIU, should > always be the case..), then we can get both benefits. We can't because it breaks compat. Previous QEMUs didn't zero the packet. > >> + p->block = qemu_ram_block_by_name(ramblock_name); >> if (!p->block) { >> - error_setg(errp, "multifd: unknown ram block %s", >> - packet->ramblock); >> + error_setg(errp, "multifd: unknown ram block %s", ramblock_name); >> return -1; >> }