Am 03.09.2025 um 09:57 hat Clément Chigot geschrieben:
> This option when set prevents a master boot record (MBR) to be
> initialized. This is mandatory as some operating system don't recognized
> mounted disks if a MBR is present.
>
> Signed-off-by: Clément Chigot <[email protected]>
Can we actually give an example of such an OS in the commit message?
> ---
> block/vvfat.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/block/vvfat.c b/block/vvfat.c
> index 814796d918..0220dd828b 100644
> --- a/block/vvfat.c
> +++ b/block/vvfat.c
> @@ -1082,6 +1082,11 @@ static QemuOptsList runtime_opts = {
> .type = QEMU_OPT_BOOL,
> .help = "Make the image writable",
> },
> + {
> + .name = "no-mbr",
> + .type = QEMU_OPT_BOOL,
> + .help = "Do not add a Master Boot Record on this disk",
> + },
Let's keep option names positive to avoid double negations like
'no-mbr=false'. We can have an 'mbr' option that defaults to true. Or in
fact, maybe calling it 'partitioned' would be easier to understand.
You need to update BlockdevOptionsVVFAT in qapi/block-core.json, too, to
make the new option work with -blockdev. You should update the
description for @floppy there, too, because it says that hard disks are
always partitioned.
It should also be added to vvfat_strong_runtime_opts because the value
of this option changes the data that the guest sees.
> { /* end of list */ }
> },
> };
> @@ -1092,6 +1097,7 @@ static void vvfat_parse_filename(const char *filename,
> QDict *options,
> int fat_type = 0;
> bool floppy = false;
> bool rw = false;
> + bool no_mbr = false;
> int i;
>
> if (!strstart(filename, "fat:", NULL)) {
> @@ -1116,6 +1122,10 @@ static void vvfat_parse_filename(const char *filename,
> QDict *options,
> rw = true;
> }
>
> + if (strstr(filename, ":no-mbr:")) {
In the string, the negative form can stay (because the positive one
doesn't exist here).
> + no_mbr = true;
> + }
> +
> /* Get the directory name without options */
> i = strrchr(filename, ':') - filename;
> assert(i >= 3);
> @@ -1131,6 +1141,7 @@ static void vvfat_parse_filename(const char *filename,
> QDict *options,
> qdict_put_int(options, "fat-type", fat_type);
> qdict_put_bool(options, "floppy", floppy);
> qdict_put_bool(options, "rw", rw);
> + qdict_put_bool(options, "no-mbr", no_mbr);
> }
>
> static int vvfat_open(BlockDriverState *bs, QDict *options, int flags,
> @@ -1196,7 +1207,10 @@ static int vvfat_open(BlockDriverState *bs, QDict
> *options, int flags,
> if (!s->fat_type) {
> s->fat_type = 16;
> }
> - s->offset_to_bootsector = 0x3f;
> + /* Reserver space for MBR */
> + if (!qemu_opt_get_bool(opts, "no-mbr", false)) {
> + s->offset_to_bootsector = 0x3f;
> + }
> cyls = s->fat_type == 12 ? 64 : 1024;
> heads = 16;
> secs = 63;
Kevin
