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David Alan Gilbert" , peterx@redhat.com, Kevin Wolf , Paolo Bonzini , =?utf-8?Q?D?= =?utf-8?Q?aniel_P_=2E_Berrang=C3=A9?= , Hailiang Zhang , Yury Kotov , Vladimir Sementsov-Ogievskiy , Prasad Pandit , Zhang Chen , Li Zhijian , Juraj Marcin , =?utf-8?Q?C?= =?utf-8?Q?=C3=A9dric?= Le Goater , "Maciej S. Szmigiero" Subject: Re: [PATCH RFC 1/9] migration/vfio: Remove BQL implication in vfio_multifd_switchover_start() In-Reply-To: <20250827205949.364606-2-peterx@redhat.com> References: <20250827205949.364606-1-peterx@redhat.com> <20250827205949.364606-2-peterx@redhat.com> Date: Tue, 16 Sep 2025 18:34:24 -0300 Message-ID: <87wm5yw07z.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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)[]; RCPT_COUNT_TWELVE(0.00)[16]; ARC_NA(0.00)[]; RBL_SPAMHAUS_BLOCKED_OPENRESOLVER(0.00)[2a07:de40:b281:104:10:150:64:97:from]; MIME_TRACE(0.00)[0:+]; FUZZY_RATELIMITED(0.00)[rspamd.com]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; RCVD_TLS_ALL(0.00)[]; TO_DN_SOME(0.00)[]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; FREEMAIL_CC(0.00)[treblig.org,redhat.com,xfusion.com,yandex-team.ru,gmail.com,fujitsu.com,maciej.szmigiero.name]; RCVD_COUNT_TWO(0.00)[2]; RCVD_VIA_SMTP_AUTH(0.00)[]; MID_RHS_MATCH_FROM(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; MISSING_XM_UA(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo, imap1.dmz-prg2.suse.org:rdns, suse.de:mid, suse.de:dkim, suse.de:email] X-Rspamd-Queue-Id: C4E3E21B0F X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action Received-SPF: pass client-ip=195.135.223.130; envelope-from=farosas@suse.de; helo=smtp-out1.suse.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 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, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=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: 2.1.29 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: > We may switch to a BQL-free loadvm model. Be prepared with it. > > Cc: C=C3=A9dric Le Goater > Cc: Maciej S. Szmigiero > Signed-off-by: Peter Xu > --- > hw/vfio/migration-multifd.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/hw/vfio/migration-multifd.c b/hw/vfio/migration-multifd.c > index e4785031a7..8dc8444f0d 100644 > --- a/hw/vfio/migration-multifd.c > +++ b/hw/vfio/migration-multifd.c > @@ -763,16 +763,21 @@ int vfio_multifd_switchover_start(VFIODevice *vbase= dev) > { > VFIOMigration *migration =3D vbasedev->migration; > VFIOMultifd *multifd =3D migration->multifd; > + bool bql_is_locked =3D bql_locked(); >=20=20 > assert(multifd); >=20=20 > /* The lock order is load_bufs_mutex -> BQL so unlock BQL here first= */ > - bql_unlock(); > + if (bql_is_locked) { > + bql_unlock(); > + } > WITH_QEMU_LOCK_GUARD(&multifd->load_bufs_mutex) { > assert(!multifd->load_bufs_thread_running); > multifd->load_bufs_thread_running =3D true; > } > - bql_lock(); > + if (bql_is_locked) { > + bql_lock(); > + } >=20=20 > qemu_loadvm_start_load_thread(vfio_load_bufs_thread, vbasedev); Reviewed-by: Fabiano Rosas