Re: [Qemu-devel] [PATCH 2/2] scsi-disk: scsi-block device for scsi pass-through should not be removable

[Paolo Bonzini <pbonzini@redhat.com>]

Il 29/05/2013 14:33, Pavel Hrdina ha scritto:
> On 29.5.2013 14:24, Paolo Bonzini wrote:
>> Il 29/05/2013 14:12, Pavel Hrdina ha scritto:
>>> This patch adds a new SCSI_DISK_F_MONITOR_NOT_REMOVABLE feature. By this
>>> feature we can set that the scsi-block (scsi pass-through) device
>>> will still
>>> be removable from the guest side, but from monitor it cannot be removed.
>>>
>>> Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
>>> ---
>>>   hw/scsi/scsi-disk.c | 10 +++++++---
>>>   1 file changed, 7 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c
>>> index c8d2a99..190c3ad 100644
>>> --- a/hw/scsi/scsi-disk.c
>>> +++ b/hw/scsi/scsi-disk.c
>>> @@ -61,8 +61,9 @@ typedef struct SCSIDiskReq {
>>>       BlockAcctCookie acct;
>>>   } SCSIDiskReq;
>>>
>>> -#define SCSI_DISK_F_REMOVABLE   0
>>> -#define SCSI_DISK_F_DPOFUA      1
>>> +#define SCSI_DISK_F_REMOVABLE               0
>>> +#define SCSI_DISK_F_DPOFUA                  1
>>> +#define SCSI_DISK_F_MONITOR_NOT_REMOVABLE   2
>>>
>>>   struct SCSIDiskState
>>>   {
>>> @@ -2107,7 +2108,8 @@ static int scsi_initfn(SCSIDevice *dev)
>>>           return -1;
>>>       }
>>>
>>> -    if (s->features & (1 << SCSI_DISK_F_REMOVABLE)) {
>>> +    if ((s->features & (1 << SCSI_DISK_F_REMOVABLE)) &&
>>> +            !(s->features & (1 <<
>>> SCSI_DISK_F_MONITOR_NOT_REMOVABLE))) {
>>>           bdrv_set_dev_ops(s->qdev.conf.bs,
>>> &scsi_disk_removable_block_ops, s);
>>>       } else {
>>>           bdrv_set_dev_ops(s->qdev.conf.bs, &scsi_disk_block_ops, s);
>>> @@ -2463,6 +2465,8 @@ static const TypeInfo scsi_cd_info = {
>>>   static Property scsi_block_properties[] = {
>>>       DEFINE_PROP_DRIVE("drive", SCSIDiskState, qdev.conf.bs),
>>>       DEFINE_PROP_INT32("bootindex", SCSIDiskState,
>>> qdev.conf.bootindex, -1),
>>> +    DEFINE_PROP_BIT("monitor_not_removable", SCSIDiskState, features,
>>> +                    SCSI_DISK_F_MONITOR_NOT_REMOVABLE, true),
>>>       DEFINE_PROP_END_OF_LIST(),
>>>   };
>>>
>>>
>>
>> I think the right fix is simply to remove
>>
>>      if (buf[1] & 0x80) {
>>          s->features |= 1 << SCSI_DISK_F_REMOVABLE;
>>      }
>>
>> from get_device_type.
>>
>> Paolo
>>
> 
> That was my first approach, but without this option it fails to start
> the guest if there was no media in the real CD-ROM.
> 
> These are the errors:
> qemu-system-x86_64: -device
> scsi-block,drive=drive-cd-disk,bus=scsi0.0,id=scsi_cd: Device needs
> media, but drive is empty
> qemu-system-x86_64: -device
> scsi-block,drive=drive-cd-disk,bus=scsi0.0,id=scsi_cd: Device
> initialization failed.
> qemu-system-x86_64: -device
> scsi-block,drive=drive-cd-disk,bus=scsi0.0,id=scsi_cd: Device
> 'scsi-block' could not be initialized

Right.  This test does not make sense for passthrough.  So if we add
another feature bit (e.g. SCSI_DISK_F_PASSTHROUGH) we can simply skip it.

Alternatively, the optimal test in the SCSI_DISK_F_PASSTHROUGH case
would be something like:

bool bdrv_is_opened(BlockDriverState *bs)
{
    return bs->drv != NULL;
}

Kevin, would you be okay with adding such a function?

Paolo