On 09/11/2010 12:24 PM, Stefan Hajnoczi wrote:
On Sat, Sep 11, 2010 at 3:04 PM, Anthony Liguori<aligu...@us.ibm.com> wrote:
This fixes a couple nasty problems relating to live migration.
1) When dealing with shared storage with weak coherence (i.e. NFS), even if
we re-read, we may end up with undesired caching. By delaying any reads
until we absolutely have to, we decrease the likelihood of any undesirable
caching.
2) When dealing with copy-on-read, the local storage acts as a cache. We need
to make sure to avoid any reads to avoid polluting the local cache.
Signed-off-by: Anthony Liguori<aligu...@us.ibm.com>
diff --git a/hw/ide/core.c b/hw/ide/core.c
index 1e466d1..57d8db3 100644
--- a/hw/ide/core.c
+++ b/hw/ide/core.c
@@ -105,6 +132,8 @@ static void ide_identify(IDEState *s)
return;
}
+ guess_geometry(s);
+
Does the same change need to be made in ide_cfata_identify()?
I quickly checked the VMStateDescription and don't see cylinders,
heads, sectors being saved for migration. I am concerned that IDE
will break after migration if the following happens:
1. Guest resumes and does not issue ATA IDENTIFY so cylinders, heads,
sectors are not initialized.
2. Normal I/O is performed, invoking ide_get_sector() which uses
geometry information that has not been initialized.
Did I miss something?
Nope, I just missed some places that need calls. I've renamed
guess_geometry() to init_geometry() and added calls to
ide_cfata_identify(), ide_get_sector(), and ide_set_sector().
That should cover it all.
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index bd6bbe6..0bf17ec 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -427,6 +427,10 @@ static void virtio_blk_update_config(VirtIODevice *vdev,
uint8_t *config)
bdrv_get_geometry(s->bs,&capacity);
bdrv_get_geometry_hint(s->bs,&cylinders,&heads,&secs);
+ if (cylinders == 0) {
+ bdrv_guess_geometry(s->bs,&cylinders,&heads,&secs);
+ }
+
bdrv_guess_geometry() can be called unconditionally. The call to
bdrv_get_geometry_hint() can be eliminated. bdrv_guess_geometry()
updates the geometry hint and does not probe the boot sector after the
first time.
Yeah, that's a fair point.
Regards,
Anthony Liguori
Stefan
