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c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1759862537; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=4xy2rq8k0KPm7HUAY4Gz4yN1sW557wyEG99y0avL/Vs=; b=g5ePCysUHshKqSUpiZeVXmhuxdN1YtcTbKDidsPtYfObY0qhD3aX01/9qD1AUc1DcgGt0Z IIvDXn4kNuWoS2Z3u+9a3e6i4cZ02mSb78259eOklyfhP4D7YlrTeqqpe2yCAxYtLjO4A+ n6081SfE2S6b1FMCz5ABIC/2I6XPPlo= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1759862537; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=4xy2rq8k0KPm7HUAY4Gz4yN1sW557wyEG99y0avL/Vs=; b=TTg9qghx7swBp+EqBF6sWjlhGhdOU3+f6lOnngbVYF1GVg0vVa3vrHaJbEkdsy1U+WRliU sKIzXPsMRIaI2LDg== From: Fabiano Rosas To: qemu-devel@nongnu.org Cc: Peter Xu , Marco Cavenati Subject: [RESEND] migration/savevm: Add a compatibility check for capabilities Date: Tue, 7 Oct 2025 15:42:13 -0300 Message-Id: <20251007184213.5990-1-farosas@suse.de> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 702D91F7EF X-Rspamd-Action: no action X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spamd-Result: default: False [-3.01 / 50.00]; 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envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; 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 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+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZohoMail-DKIM: pass (identity @suse.de) X-ZM-MESSAGEID: 1759862612788154100 Content-Type: text/plain; charset="utf-8" It has always been possible to enable arbitrary migration capabilities and attempt to take a snapshot of the VM with the savevm/loadvm commands as well as their QMP counterparts snapshot-save/snapshot-load. Most migration capabilities are not meant to be used with snapshots and there's a risk of crashing QEMU or producing incorrect behavior. Ideally, every migration capability would either be implemented for savevm or explicitly rejected. Add a compatibility check routine and reject the snapshot command if an incompatible capability is enabled. For now only act on the the two that actually cause a crash: multifd and mapped-ram. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2881 Signed-off-by: Fabiano Rosas --- migration/options.c | 27 +++++++++++++++++++++++++++ migration/options.h | 1 + migration/savevm.c | 8 ++++++++ 3 files changed, 36 insertions(+) diff --git a/migration/options.c b/migration/options.c index 5183112775..d9227809d7 100644 --- a/migration/options.c +++ b/migration/options.c @@ -445,11 +445,38 @@ INITIALIZE_MIGRATE_CAPS_SET(check_caps_background_sna= pshot, MIGRATION_CAPABILITY_VALIDATE_UUID, MIGRATION_CAPABILITY_ZERO_COPY_SEND); =20 +/* Snapshot compatibility check list */ +static const +INITIALIZE_MIGRATE_CAPS_SET(check_caps_savevm, + MIGRATION_CAPABILITY_MULTIFD, + MIGRATION_CAPABILITY_MAPPED_RAM, +); + static bool migrate_incoming_started(void) { return !!migration_incoming_get_current()->transport_data; } =20 +bool migrate_can_snapshot(Error **errp) +{ + MigrationState *s =3D migrate_get_current(); + int i; + + for (i =3D 0; i < check_caps_savevm.size; i++) { + int incomp_cap =3D check_caps_savevm.caps[i]; + + if (s->capabilities[incomp_cap]) { + error_setg(errp, + "Snapshots are not compatible with %s", + MigrationCapability_str(incomp_cap)); + return false; + } + } + + return true; +} + + bool migrate_rdma_caps_check(bool *caps, Error **errp) { if (caps[MIGRATION_CAPABILITY_XBZRLE]) { diff --git a/migration/options.h b/migration/options.h index 82d839709e..a7b3262d1e 100644 --- a/migration/options.h +++ b/migration/options.h @@ -59,6 +59,7 @@ bool migrate_tls(void); =20 bool migrate_rdma_caps_check(bool *caps, Error **errp); bool migrate_caps_check(bool *old_caps, bool *new_caps, Error **errp); +bool migrate_can_snapshot(Error **errp); =20 /* parameters */ =20 diff --git a/migration/savevm.c b/migration/savevm.c index 7b35ec4dd0..aafa40d779 100644 --- a/migration/savevm.c +++ b/migration/savevm.c @@ -3322,6 +3322,10 @@ bool save_snapshot(const char *name, bool overwrite,= const char *vmstate, =20 GLOBAL_STATE_CODE(); =20 + if (!migrate_can_snapshot(errp)) { + return false; + } + if (migration_is_blocked(errp)) { return false; } @@ -3507,6 +3511,10 @@ bool load_snapshot(const char *name, const char *vms= tate, int ret; MigrationIncomingState *mis =3D migration_incoming_get_current(); =20 + if (!migrate_can_snapshot(errp)) { + return false; + } + if (!bdrv_all_can_snapshot(has_devices, devices, errp)) { return false; } --=20 2.35.3