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Tsirkin" , Paolo Bonzini , Fam Zheng , Manos Pitsidianakis Subject: [PATCH v2 5/8] migration: Add VMS_NO_STATE flag Date: Tue, 18 Aug 2026 15:24:38 -0300 Message-ID: <20260818182441.404790-6-farosas@suse.de> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260818182441.404790-1-farosas@suse.de> References: <20260818182441.404790-1-farosas@suse.de> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spamd-Result: default: False [-3.01 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; MID_CONTAINS_FROM(1.00)[]; R_MISSING_CHARSET(0.50)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; NEURAL_HAM_SHORT(-0.20)[-0.999]; MIME_GOOD(-0.10)[text/plain]; MX_GOOD(-0.01)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo,suse.de:email,suse.de:mid,suse.de:dkim]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; MIME_TRACE(0.00)[0:+]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; RCPT_COUNT_SEVEN(0.00)[8]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Queue-Id: 69704846C1 X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Rspamd-Action: no action Received-SPF: pass client-ip=2a07:de40:b251:101:10:150:64:1; envelope-from=farosas@suse.de; helo=smtp-out1.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: qemu development 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 There are a few special cases of vmstate usage: The vmstate_msix and vmstate_scsi_device have fields that contain no data, only a vmstate_info structure. The VMSTATE_VALIDATE macro serves only to invoke the .field_exists routine for validation. Regardless whether these scenarios are valid, add a separate flag to identify them so we can enforce common constraints for the normal vmstates such as having a size greater than zero. Note that n_elems is hardcoded to 1 for all vmstates, except VMS_[V]ARRAY, so VMSTATE_VALIDATE needed to set VMS_ARRAY to be able to force n_elems to 0. This patch now checks the flag at vmstate_n_elems(). Signed-off-by: Fabiano Rosas --- hw/pci/msix.c | 6 +----- hw/scsi/scsi-bus.c | 6 +----- include/migration/vmstate.h | 9 +++++++-- migration/vmstate.c | 6 +++++- rust/migration/src/vmstate.rs | 2 +- rust/tests/tests/vmstate_tests.rs | 2 +- 6 files changed, 16 insertions(+), 15 deletions(-) diff --git a/hw/pci/msix.c b/hw/pci/msix.c index 1b23eaf1007..adf76b5bccc 100644 --- a/hw/pci/msix.c +++ b/hw/pci/msix.c @@ -711,12 +711,8 @@ const VMStateDescription vmstate_msix = { .fields = (const VMStateField[]) { { .name = "msix", - .version_id = 0, - .field_exists = NULL, - .size = 0, /* ouch */ .info = &vmstate_info_msix, - .flags = VMS_SINGLE, - .offset = 0, + .flags = VMS_SINGLE | VMS_NO_STATE, }, VMSTATE_END_OF_LIST() } diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c index deb43d5560e..aa02ff631b7 100644 --- a/hw/scsi/scsi-bus.c +++ b/hw/scsi/scsi-bus.c @@ -1980,12 +1980,8 @@ const VMStateDescription vmstate_scsi_device = { VMSTATE_UINT32(sense_len, SCSIDevice), { .name = "requests", - .version_id = 0, - .field_exists = NULL, - .size = 0, /* ouch */ .info = &vmstate_info_scsi_requests, - .flags = VMS_SINGLE, - .offset = 0, + .flags = VMS_SINGLE | VMS_NO_STATE, }, VMSTATE_END_OF_LIST() }, diff --git a/include/migration/vmstate.h b/include/migration/vmstate.h index 4b6d52955ff..e72c3fae9a6 100644 --- a/include/migration/vmstate.h +++ b/include/migration/vmstate.h @@ -109,6 +109,12 @@ enum VMStateFlags { */ VMS_ARRAY_OF_POINTER = 0x040, + /* + * The field contains no data. Used for special cases such as + * invoking a custom VMStateInfo. + */ + VMS_NO_STATE = 0x080, + /* The size of the individual entries (a single array entry if * VMS_ARRAY or VMS_VARRAY are set, or the field itself if * neither is set) is variable (i.e. not known at compile-time), @@ -454,8 +460,7 @@ extern const VMStateInfo vmstate_info_g_byte_array; #define VMSTATE_VALIDATE(_name, _test) { \ .name = (_name), \ .field_exists = (_test), \ - .flags = VMS_ARRAY | VMS_MUST_EXIST, \ - .num = 0, /* 0 elements: no data, only run _test */ \ + .flags = VMS_MUST_EXIST | VMS_NO_STATE, \ } #define VMSTATE_POINTER(_field, _state, _version, _info, _type) { \ diff --git a/migration/vmstate.c b/migration/vmstate.c index bc5285bcea2..51d02b87e7e 100644 --- a/migration/vmstate.c +++ b/migration/vmstate.c @@ -97,12 +97,16 @@ static uint64_t vmstate_read_from_offset(const VMStateStructMember *member, static uint64_t vmstate_n_elems(void *opaque, const VMStateField *field) { - uint64_t n_elems = 1; + uint64_t n_elems; if (field->flags & VMS_ARRAY) { n_elems = field->num; } else if (field->flags & VMS_VARRAY) { n_elems = vmstate_read_from_offset(&field->num_indirect, opaque); + } else if (field->flags & VMS_MUST_EXIST && field->flags & VMS_NO_STATE) { + n_elems = 0; + } else { + n_elems = 1; } trace_vmstate_n_elems(field->name, n_elems); diff --git a/rust/migration/src/vmstate.rs b/rust/migration/src/vmstate.rs index 4ec54097148..a3a710ab3ac 100644 --- a/rust/migration/src/vmstate.rs +++ b/rust/migration/src/vmstate.rs @@ -418,7 +418,7 @@ macro_rules! vmstate_validate { field_exists: $crate::vmstate_exist_fn!($struct_name, $test_fn), flags: $crate::bindings::VMStateFlags( $crate::bindings::VMStateFlags::VMS_MUST_EXIST.0 - | $crate::bindings::VMStateFlags::VMS_ARRAY.0, + | $crate::bindings::VMStateFlags::VMS_NO_STATE.0, ), num: 0, // 0 elements: no data, only run test_fn callback ..::common::zeroable::Zeroable::ZERO diff --git a/rust/tests/tests/vmstate_tests.rs b/rust/tests/tests/vmstate_tests.rs index 5f6dd8ae7f1..6578d54b37d 100644 --- a/rust/tests/tests/vmstate_tests.rs +++ b/rust/tests/tests/vmstate_tests.rs @@ -461,7 +461,7 @@ fn test_vmstate_validate() { assert_eq!(foo_fields[0].num, 0); assert_eq!( foo_fields[0].flags.0, - VMStateFlags::VMS_ARRAY.0 | VMStateFlags::VMS_MUST_EXIST.0 + VMStateFlags::VMS_NO_STATE.0 | VMStateFlags::VMS_MUST_EXIST.0 ); assert!(foo_fields[0].vmsd.is_null()); assert!(unsafe { foo_fields[0].field_exists.unwrap()(foo_d_p, 0) }); -- 2.53.0