Re: [Qemu-devel] [PATCH 05/12] S390: ccw firmware: Add main program

[Cornelia Huck]

On Tue, 23 Apr 2013 13:35:47 +0200
Alexander Graf <address@hidden> wrote:

> On 04/23/2013 10:58 AM, Cornelia Huck wrote:
> > On Mon, 22 Apr 2013 21:18:11 +0200
> > Alexander Graf<address@hidden>  wrote:
> >
> >> This C file is the main driving piece of the s390 ccw firmware. It
> >> provides a search for a workable block device, sets it as the default
> >> to boot off of and boots from it.
> >>
> >> Signed-off-by: Alexander Graf<address@hidden>
> >> ---
> >>   pc-bios/s390-ccw/main.c |   56 
> >> +++++++++++++++++++++++++++++++++++++++++++++++
> >>   1 files changed, 56 insertions(+), 0 deletions(-)
> >>   create mode 100644 pc-bios/s390-ccw/main.c
> >>
> >> diff --git a/pc-bios/s390-ccw/main.c b/pc-bios/s390-ccw/main.c
> >> new file mode 100644
> >> index 0000000..0913aac
> >> --- /dev/null
> >> +++ b/pc-bios/s390-ccw/main.c
> >> @@ -0,0 +1,56 @@
> >> +/*
> >> + * S390 virtio-ccw loading program
> >> + *
> >> + * Copyright (c) 2013 Alexander Graf<address@hidden>
> >> + *
> >> + * This work is licensed under the terms of the GNU GPL, version 2 or (at
> >> + * your option) any later version. See the COPYING file in the top-level
> >> + * directory.
> >> + */
> >> +
> >> +#include "s390-ccw.h"
> >> +
> >> +struct subchannel_id blk_schid;
> >> +char stack[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
> >> +
> >> +void virtio_panic(const char *string)
> >> +{
> >> +    sclp_print(string);
> >> +    while (1) { }
> >> +}
> >> +
> >> +static void virtio_setup(void)
> >> +{
> >> +    struct irb irb;
> >> +    int i;
> >> +    int r;
> >> +    bool found = false;
> >> +
> >> +    blk_schid.one = 1;
> >> +
> >> +    for (i = 0; i<  0x10000; i++) {
> >> +        blk_schid.sch_no = i;
> >> +        r = tsch(blk_schid,&irb);
> > You want to do a stsch() loop here, not a tsch() loop :)
> 
> What does stsch buy us over tsch?

A stsch() loop is the canonical way to find devices. tsch() is for
updating subchannel status.

And:
 
> > As a bonus, you can exit the loop on cc == 3.

:)

> >
> >             r = stsch(blk_schid,&schib);
> >        if (r == 3) {
> >           break;
> >        }
> >
> >> +        if (r != 3) {
> >             if (schib.pmcw.dnv) {
> >
> >> +            if (virtio_is_blk(blk_schid)) {
> >> +                found = true;
> >> +                break;
> >> +            }
> >> +        }
> >> +    }
> >> +
> >> +    if (!found) {
> >> +        virtio_panic("No virtio-blk device found!\n");
> >> +    }
> >> +
> >> +    virtio_setup_block(blk_schid);
> > The virtio_is_blk() and virtio_setup_block() functions should go into a
> > preceding patch, no?
> 
> The code doesn't get compiled before the end of the series anyway, so 
> ordering might be slightly off :)
> 
> 
> Alex
>