kvmvapic: patch_instruction fix

When QEMU works in icount mode cpu_restore_state function performs two actions:
restoring the program counter and updating icount to the correct value.
kvmvapic's patch_instruction function is called by cpu_report_tpr_access
function which also invokes cpu_restore_state. It results to calling
cpu_restore_state twice - in cpu_report_tpr_access and in patch_instruction.
When icount is disabled second call is safe. But when icount is enabled,
cpu_restore_state modifies instructions counter twice, which leads to incorrect
behavior. This patch removes useless cpu_restore_state call from kvmvapic.

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>
iscsi: Refuse to open as writable if the LUN is write protected

Before, when a write protected iSCSI target is attached as scsi-disk
with BDRV_O_RDWR, we report it as writable, while in fact all writes
will fail.

One way to improve this is to report write protect flag as true to
guest, but a even better way is to refuse using a write protected LUN to
guest.

Target write protect flag is checked with a mode sense query.

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
virtio-scsi: Fix memory leak when realize failed

Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
scsi: devirtualize unrealize of SCSI devices

All implementations are the same.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>