From: "Dr. David Alan Gilbert" <dgilb...@redhat.com> Add information on the QEMUFile/Visitor/VMState split Describe how to verify a BER stream against the schema
Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com> --- docs/migration.txt | 34 ++++++++++++++++++++++++++++++++-- 1 file changed, 32 insertions(+), 2 deletions(-) diff --git a/docs/migration.txt b/docs/migration.txt index 0e0a1d4..894abf3 100644 --- a/docs/migration.txt +++ b/docs/migration.txt @@ -48,8 +48,17 @@ This is used for RAM and block devices. It is not yet ported to vmstate. === What is the common infrastructure === -QEMU uses a QEMUFile abstraction to be able to do migration. Any type -of migration that wants to use QEMU infrastructure has to create a +Migration consists of a number of layers that handle different parts of the +problem: + QEMUFile - Buffering/reading/writing data without worrying about it's + contents. Versions exist for file I/O, sockets, RDMA and + to put data into a QEMU Block device. + Visitor - Visitors format data onto the QEMUFile. A binary format and + a BER format currently exist. + VMState - Represent the structure of the data for a given device with + support for versioning. + +Any type of migration that wants to use QEMU infrastructure has to create a QEMUFile with: QEMUFile *qemu_fopen_ops(void *opaque, @@ -296,3 +305,24 @@ save/send this state when we are in the middle of a pio operation (that is what ide_drive_pio_state_needed() checks). If DRQ_STAT is not enabled, the values on that fields are garbage and don't need to be sent. + +ASN.1/BER format migration +========================== + +In BER format migration the migration stream is described by an ASN.1 schema +(that's defined in docs/specs/migration.schema). + +The 'asn1c' program can be used to validate a migration stream against the schema + - although it'll probably use a lot of memory doing it - so it's best to do it +with a small RAM image. + +To validate an image against the schema: + a) Make a temporary directory and cd into it + b) asn1c -fcompound-names /path/to/migration.schema + c) make -f Makefile.am.sample CFLAGS+="-DPDU=QemuFile -DEMIT_ASN_DEBUG=1 -I." + d) ./progname -iber log.ber -d 2> debug > decoding + + If it's happy the 'decoding' output should be an XML like dump of the input file; +if it's not happy, the debug file might help you find out why (Search backwards +from the end for the first 'Freeing' to find the point at which it detected something +bad). -- 1.8.5.3