Re: [Qemu-devel] [PATCH 1/3] tests/boot-sector: Add magic bytes to s390x boot code header

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, Mar 15, 2018 at 12:47:08PM +0100, Philippe Mathieu-Daudé wrote:
> On 03/15/2018 08:49 AM, Thomas Huth wrote:
> > We're going to use the s390x boot code for testing CD-ROM booting.
> > But the ISO loader of the s390-ccw bios is a little bit more picky
> > than the network loader and expects some magic bytes in the header
> > of the file (see linux_s390_magic in pc-bios/s390-ccw/bootmap.c), so
> > we've got to add them in our boot code here, too.
> > 
> > Signed-off-by: Thomas Huth <thuth@redhat.com>
> > ---
> >  tests/boot-sector.c | 9 ++++++---
> >  1 file changed, 6 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tests/boot-sector.c b/tests/boot-sector.c
> > index c373f0e..04721c9 100644
> > --- a/tests/boot-sector.c
> > +++ b/tests/boot-sector.c
> > @@ -68,8 +68,11 @@ static uint8_t x86_boot_sector[512] = {
> >  };
> >  
> >  /* For s390x, use a mini "kernel" with the appropriate signature */
> > -static const uint8_t s390x_psw[] = {
> > -    0x00, 0x08, 0x00, 0x00, 0x80, 0x01, 0x00, 0x00
> > +static const uint8_t s390x_psw_and_magic[] = {
> 
> Can you add a comment such "see linux_s390_magic in
> pc-bios/s390-ccw/bootmap.c"?

Or better yet, copy the code comment from there.

> > +    0x00, 0x08, 0x00, 0x00, 0x80, 0x01, 0x00, 0x00,
> > +    0x02, 0x00, 0x00, 0x18, 0x60, 0x00, 0x00, 0x50,
> > +    0x02, 0x00, 0x00, 0x68, 0x60, 0x00, 0x00, 0x50,
> > +    0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40, 0x40
> >  };
> >  static const uint8_t s390x_code[] = {
> >      0xa7, 0xf4, 0x00, 0x0a,                                /* j 0x10010 */
> > @@ -110,7 +113,7 @@ int boot_sector_init(char *fname)
> >      } else if (g_str_equal(arch, "s390x")) {
> >          len = 0x10000 + sizeof(s390x_code);
> >          boot_code = g_malloc0(len);
> > -        memcpy(boot_code, s390x_psw, sizeof(s390x_psw));
> > +        memcpy(boot_code, s390x_psw_and_magic, sizeof(s390x_psw_and_magic));
> >          memcpy(&boot_code[0x10000], s390x_code, sizeof(s390x_code));
> >      } else {
> >          g_assert_not_reached();
> >