The IDE PIO interface currently uses bdrv_read() to perform reads
synchronously. Synchronous I/O in the vcpu thread is bad because it
prevents the guest from executing code - it makes the guest
unresponsive.
This patch converts IDE PIO to use bdrv_aio_readv(). We simply need to
use the BUSY_STAT status so the guest knows to wait while we are busy.
The only external user of ide_sector_read() is restart behavior on I/O
errors and it is not affected by this change. We still need to restart
I/O in the same way.
Migration is also unaffected if I understand the code correctly. We
continue to use the same transfer function and the BUSY_STAT status
should never be migrated since we flush I/O before migrating device
state.
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Tested-by: Richard Davies <richard@arachsys.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
bef0fd5958