* Michael S. Tsirkin (m...@redhat.com) wrote:
> On Fri, Mar 07, 2014 at 04:55:03PM +0000, Dr. David Alan Gilbert wrote:
<snip>
> I think this is already useful.
> For example this will make input parser
> more robust against unexpected input
> as octet string blobs are bounded, so if we fail
> to parse one we at least will not
> interpret it as beginning of the next one.
I've also managed (with a slightly improved schema
at the end) to validate my output sequence against the schema
using asn1c (once I'd persuaded it to build stuff and turn
it's debug on).
> I think it's a good idea to merge this gradually,
> even if this means changing format several times:
> as long as we can stay compatible with old machine
> types.
Yes, that would make the merge easier.
> > --------------------------------------------------------------------------------
> >
> > Qemu {}
> > DEFINITIONS IMPLICIT TAGS ::=
> > BEGIN
> >
> > -- Some basic types used in multiple places --
> > QemuString ::= UTF8String (SIZE (1..255))
> >
> > -- TODO: 4096 is actually page size whatever that is
> > FullPage ::= OCTET STRING (SIZE (4096))
> >
> > RAMBlockID ::= SEQUENCE {
> > name QemuString,
> > len INTEGER
>
> is len needed here?
>
> > }
> >
> > RAMSecEntry ::= [ APPLICATION 8914 ] SEQUENCE {
> > addr INTEGER, -- Address or offset or size
>
> hmm so which one?
>
> > flags INTEGER, -- maybe more explicit type?
> > name QemuString OPTIONAL,
> >
> > body CHOICE {
> > bl SEQUENCE OF RAMBlockID,
> > compr INTEGER (0..255), -- Page filled with this value
> > page FullPage
> > -- TODO xbzrle --
>
> this one confused me.
> I expected RAMBlockID followed by a sequence of pages
I've kept with the structure of the way the migrate works at the moment;
it transmits the 'shape' of RAM as a list of name/length pairs, and only
once it's validated that it has all the RAM blocks and their lengths match
does it start shifting pages across.
This a RAM section is either the initialisation data (the sequence of
RAMBlockID's)
or a stream of pages.
I don't think it's a bad idea to have that RAM list at the beginning,
it catches a lot of silly mismatches - if you've ever hit a complaint
about a mismatched BIOS length or a missing ROM, it's probably come
from the check of this incoming list.
The existing binary format is a stream of things separated by a
64bit int that is an address/offset/or size depending on some bits OR'd
into the bottom of the address; I'd currently split the flags out
of that 64bit int, but hadn't split that further yet.
I'm thinking of splitting this down further, especially so I can
reduce the size of 'all 0' pages.
> >
> > RAMSecList ::= [ APPLICATION 9810 ] SEQUENCE OF RAMSecEntry
> >
> > SubSection ::= [ APPLICATION 10707 ] SEQUENCE {
> > name QemuString,
> > versionid INTEGER,
> >
> > contents SEQUENCE OF VMStateEntries
> > }
> >
> > SubSecList ::= [ APPLICATION 10700 ] SEQUENCE OF SubSection
> >
> > VMStateEntries ::= CHOICE {
> > -- Hmm need to think more --
>
> I'm guessing individual devices will have
> tagged entries here?
I'm thinking of *allowing* individual devices to have
tagged entries here, but I don't think I'd require it - since
to require it would mean I'd have to change every existing
VMState to give it a tag.
So I was going to allow VMStateEntries to be a generic set
using universal tags, which we could add specific entries
where we'd given common devices full tags.
> > dummy INTEGER,
>
> why is this here?
It's one of the universal entries; my current full version (that
verifies) is:
VMStateEntries ::= CHOICE {
-- Hmm need to think more --
array SEQUENCE OF VMStateEntries,
bool BOOLEAN,
int INTEGER,
oldblob OCTET STRING,
subsecl SubSecList
}
>
> > subsecl SubSecList,
> > oldblob OCTET STRING
> > }
> >
> > VMState ::= SEQUENCE OF VMStateEntries
> >
> > -- Restrict to unsigned?
> > SectionID ::= INTEGER
> >
> > SecFull ::= [ APPLICATION 2003 ] SEQUENCE {
> > name QemuString,
> > sectionid SectionID,
>
> what is this id exactly?
It's again a hold over from the old format; Sections
come in two varieties 'Full' and 'Min'; 'Full'
sections are typically used for devices that just get
sent once, and thus have a name - the ID doesn't
really do much for them; however devices that send
data iteratively send a Full followed by a series of
Min's - each Min just has the SectionID matching the Full,
so it saves it having to send the name each time,
and it also means that it just has an index rather
than having to string compare the name for every
section.
Note that iterative devices can be interleaved so
you might have some RAM, followed by some disk blocks
and then some more RAM etc, which is why you can't
just have a sequence of pages.
Dave
P.S. Here's the current verison of my schema which
validates against my ber data.
Qemu {}
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
-- Some basic types used in multiple places --
QemuString ::= UTF8String (SIZE (1..255))
-- TODO: 4096 is actually page size whatever that is
FullPage ::= OCTET STRING (SIZE (4096))
RAMBlockID ::= SEQUENCE {
name QemuString,
len INTEGER
}
RAMSecEntry ::= [ APPLICATION 8914 ] SEQUENCE {
addr INTEGER, -- Address or offset or size
flags INTEGER, -- maybe more explicit type?
name QemuString OPTIONAL,
body CHOICE {
bl SEQUENCE OF RAMBlockID,
compr INTEGER (0..255), -- Page filled with this value
page FullPage
-- TODO xbzrle --
}
}
RAMSecList ::= [ APPLICATION 9810 ] SEQUENCE OF RAMSecEntry
SubSection ::= [ APPLICATION 10707 ] SEQUENCE {
name QemuString,
versionid INTEGER,
contents SEQUENCE OF VMStateEntries
}
SubSecList ::= [ APPLICATION 10700 ] SEQUENCE OF SubSection
VMStateEntries ::= CHOICE {
-- Hmm need to think more --
array SEQUENCE OF VMStateEntries,
bool BOOLEAN,
int INTEGER,
oldblob OCTET STRING,
subsecl SubSecList
}
VMState ::= SEQUENCE OF VMStateEntries
-- Restrict to unsigned?
SectionID ::= INTEGER
SecFull ::= [ APPLICATION 2003 ] SEQUENCE {
name QemuString,
sectionid SectionID,
instanceid INTEGER,
versionid INTEGER,
contents CHOICE {
ramsec RAMSecList,
-- TODO other iterator initial stuff --
vmstate VMState,
oldblob OCTET STRING
}
}
SecMin ::= [ APPLICATION 211 ] SEQUENCE {
sectionid SectionID,
contents CHOICE {
ramsec RAMSecList
-- TODO other iterator general/end stuff --
}
}
Sections ::= CHOICE {
full SecFull,
min SecMin
}
-- The whole file --
-- Application tag used to get first 32bits of file
-- to come out as 7f cd c5 51 - the 51 is Q
-- the c5 and cd being E,M but with the top bit set
-- which BER requires
QemuFile ::= [ APPLICATION 1270481 ] SEQUENCE {
version INTEGER (3),
top SEQUENCE OF Sections
}
END
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
