[Qemu-devel] Re: [patch]Fix block device read for some SLOW file

[Jani Monoses]

lepton wrote:
> Hi, I found when I am using qemu, I can't boot from emulated cdrom.
> After some debug, I found the reason is that my iso file is in a samba
> file system. When qemu read data from my samba file system. read will be
> interrupted by signal alarm. So qemu won't boot from it.
>
> The follwing patch will fix it.
>
> --- qemu-0.7.1/block.c  2005-07-25 02:52:08.000000000 +0800
> +++ qemu-0.7.1-lepton/block.c   2005-07-27 18:57:21.000000000 +0800
> @@ -591,10 +591,16 @@ static int raw_read(BlockDriverState *bs
>      int ret;
>      
>      lseek(s->fd, sector_num * 512, SEEK_SET);
> -    ret = read(s->fd, buf, nb_sectors * 512);
> -    if (ret != nb_sectors * 512) 
> -        return -1;
> -    return 0;

There's another error related to this code: qemu won't boot floppy images whose size isn't 
a multiple of 512, it will drop the last incomplete sector, as the last read will not give 
512 bytes.
a good testcase is the asmutils linux floppy image.

Jani