[Qemu-devel] [PATCH/RFC 1/2] s390-ccw.img: Allow bigger ramdisk sizes or offsets

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

The s390-ccw bios creates the the virtqueue at 100MB. For
big ramdisks or offsets (via zipl) this gets overwritten.
As a quick band-aid, lets move the virtqueue into the bss
section, which is at 0x7f00000. As the bios code (text) is
at 0x7e00000 we can now handle ramdisk which are  ~27MB
bigger.

Long term we want to make the s390-ccw bios position
independent and load of at the end of memory.

Reported-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
---
 pc-bios/s390-ccw/main.c     | 1 +
 pc-bios/s390-ccw/s390-ccw.h | 1 +
 pc-bios/s390-ccw/virtio.c   | 4 ++--
 3 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/pc-bios/s390-ccw/main.c b/pc-bios/s390-ccw/main.c
index 6f707bb..584d4a2 100644
--- a/pc-bios/s390-ccw/main.c
+++ b/pc-bios/s390-ccw/main.c
@@ -12,6 +12,7 @@
 #include "virtio.h"
 
 char stack[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
+char ring_area[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
 uint64_t boot_value;
 static struct subchannel_id blk_schid = { .one = 1 };
 
diff --git a/pc-bios/s390-ccw/s390-ccw.h b/pc-bios/s390-ccw/s390-ccw.h
index ceb7418..9b3868b 100644
--- a/pc-bios/s390-ccw/s390-ccw.h
+++ b/pc-bios/s390-ccw/s390-ccw.h
@@ -52,6 +52,7 @@ void disabled_wait(void);
 void virtio_panic(const char *string);
 void write_subsystem_identification(void);
 extern char stack[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
+extern char ring_area[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
 extern uint64_t boot_value;
 
 /* sclp-ascii.c */
diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c
index bdf5810..57ff1b0 100644
--- a/pc-bios/s390-ccw/virtio.c
+++ b/pc-bios/s390-ccw/virtio.c
@@ -379,10 +379,10 @@ void virtio_setup_block(struct subchannel_id schid)
     if (run_ccw(schid, CCW_CMD_READ_CONF, &blk_cfg, sizeof(blk_cfg))) {
         virtio_panic("Could not get block device configuration\n");
     }
-    vring_init(&block, config.num, (void *)(100 * 1024 * 1024),
+    vring_init(&block, config.num, ring_area,
                KVM_S390_VIRTIO_RING_ALIGN);
 
-    info.queue = (100ULL * 1024ULL* 1024ULL);
+    info.queue = (unsigned long long) ring_area;
     info.align = KVM_S390_VIRTIO_RING_ALIGN;
     info.index = 0;
     info.num = config.num;
-- 
2.3.0