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Re: [Qemu-devel] [PATCH 4/4] blocksize: add blkconf_blocksize call to al
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH 4/4] blocksize: add blkconf_blocksize call to all block devices |
Date: |
Wed, 17 Sep 2014 15:00:15 +0100 |
User-agent: |
Mutt/1.5.23 (2014-03-12) |
On Thu, Sep 04, 2014 at 02:28:26PM +0400, Ekaterina Tumanova wrote:
> On 09/03/2014 07:46 PM, Stefan Hajnoczi wrote:
> >On Tue, Jul 29, 2014 at 02:27:19PM +0200, Ekaterina Tumanova wrote:
> >>This patch add the blkconf_blocksize call to all
> >>devices, which use DEFINE_BLOCK_PROPERTIES.
> >>If the underlying driver function fails, blkconf_blocksizes
> >>will set blocksizes to default (512) value.
> >>
> >>Signed-off-by: Ekaterina Tumanova <address@hidden>
> >>Reviewed-by: David Hildenbrand <address@hidden>
> >>Acked-by: Cornelia Huck <address@hidden>
> >>---
> >> hw/block/nvme.c | 1 +
> >> hw/block/virtio-blk.c | 1 +
> >> hw/ide/qdev.c | 1 +
> >> hw/scsi/scsi-disk.c | 1 +
> >> hw/usb/dev-storage.c | 1 +
> >> include/hw/block/block.h | 4 ++--
> >> 6 files changed, 7 insertions(+), 2 deletions(-)
> >
> >Wasn't this NACKed before on the grounds that it is likely to upset the
> >guest after live migration? QEMU doesn't automatically query the
> >storage because these parameters must be preserved across migration.
> >
>
> Sorry, haven't found this discussion in the mail list. Do you have a link?
I don't have the link but am referring to the last time these patches
were discussed - ~1 year ago?
> As far as I understand, the xxxxxx_init functions of the qemu block devices,
> which contain blkconf_blocksize calls, will
> be called again on the destination host before the guest is resumed. And
> since migration requests qemu to be brought on the same disk, the
> configuration will receive the same block size from the ioctl, as
> before. What do I miss?
Live storage migration is supported. This means non-shared storage is
possible.
Therefore the host block device that a guest runs on can change.
> >If you want specific parameters, please put them in your guest
> >configuration. QEMU and libvirt support that.
> >
> >I'm concerned that this patch serious is likely to break things and
> >autodetection doesn't add much value since the management tool needs to
> >be aware of this information anyway.
> >
>
> Can you please explain what do you mean by "AUTOdetection"?
> Do you simply mean "detection by ioctl" or "detection performed without
> guest request"?
I mean passing through the host block device attributes to the guest.
Stefan
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