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

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 22/04/13 21:18, Alexander Graf 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 <agraf@suse.de>
> ---
>  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 <agraf@suse.de>
> + *
> + * 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);
> +        if (r != 3) {
> +            if (virtio_is_blk(blk_schid)) {
> +                found = true;
> +                break;
> +            }
> +        }
> +    }
> +
> +    if (!found) {
> +        virtio_panic("No virtio-blk device found!\n");
> +    }
> +
> +    virtio_setup_block(blk_schid);
> +}
> +
> +int main(void)
> +{
> +    sclp_setup();

The sclp patch should probably be moved before this one...

> +    virtio_setup();
> +    if (zipl_load() < 0)

...as well as the bootmap loader

> +        sclp_print("Failed to load OS from hard disk\n");
> +    while (1) { }

This would waste host cpus spinning, no?

Please do a disabled wait. The easiest way might be a short assember routine:

.globl disabled_wait
disabled_wait:
	larl %r1,disabled_wait_psw
	lpswe	0(%r1)

        .align  8
disabled_wait_psw:
        .quad   0x0002000180000000,0x0000000000000000