Vitaly Kuznetsov <[email protected]> writes: > It was found that 'qemu-nbd' is not able to work with some disk images > exported from Azure. Looking at the 512b footer (which contains VPC > metadata): > > 00000000 63 6f 6e 65 63 74 69 78 00 00 00 02 00 01 00 00 |conectix........| > 00000010 ff ff ff ff ff ff ff ff 2e c7 9b 96 77 61 00 00 |............wa..| > 00000020 00 07 00 00 57 69 32 6b 00 00 00 01 40 00 00 00 |....Wi2k....@...| > 00000030 00 00 00 01 40 00 00 00 28 a2 10 3f 00 00 00 02 |....@...(..?....| > 00000040 ff ff e7 47 8c 54 df 94 bd 35 71 4c 94 5f e5 44 |...G.T...5qL._.D| > 00000050 44 53 92 1a 00 00 00 00 00 00 00 00 00 00 00 00 |DS..............| > 00000060 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| > > we can see that Azure uses a different 'Creator application' -- > 'wa\0\0' (offset 0x1c, likely reads as 'Windows Azure') and QEMU uses this > field to determine how it can get image size. Apparently, Azure uses 'new' > method, just like Hyper-V. > > Signed-off-by: Vitaly Kuznetsov <[email protected]> > --- > Alternatively, we can probably make 'current_size' the default and only use > CHS for 'vpc '/'qemu'. > --- > block/vpc.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/block/vpc.c b/block/vpc.c > index d95a204612b7..da8662402d00 100644 > --- a/block/vpc.c > +++ b/block/vpc.c > @@ -321,6 +321,7 @@ static int vpc_open(BlockDriverState *bs, QDict *options, > int flags, > * 'qemu' : CHS QEMU (uses disk geometry) > * 'qem2' : current_size QEMU (uses current_size) > * 'win ' : current_size Hyper-V > + * 'wa\0\0': current_size Azure > * 'd2v ' : current_size Disk2vhd > * 'tap\0' : current_size XenServer > * 'CTXS' : current_size XenConverter > @@ -330,6 +331,7 @@ static int vpc_open(BlockDriverState *bs, QDict *options, > int flags, > * that have CHS geometry of the maximum size. > */ > use_chs = (!!strncmp(footer->creator_app, "win ", 4) && > + !!strncmp(footer->creator_app, "wa", 4) &&
Stupid me forgot how strncmp() works wrt '\0' bytes, I think we're better off doing plain memcmp() instead. I'll send v2. > !!strncmp(footer->creator_app, "qem2", 4) && > !!strncmp(footer->creator_app, "d2v ", 4) && > !!strncmp(footer->creator_app, "CTXS", 4) && -- Vitaly
