Re: [Qemu-devel] [PATCH 05/15] scsi: pass residual amount to command_complete

[Paolo Bonzini]

On 02/10/2012 12:44 PM, Stefan Hajnoczi wrote:
> > > +static void esp_command_complete(SCSIRequest *req, uint32_t status,
> > > +                                 int32_t resid)
> Is there a reason to use a signed type for resid?  (I expected
> uint32_t to be safer and more natural.)

It's a mess; req->cmd.xfer is a size_t, but it should be an uint64_t 
with tests that it doesn't overflow (for example if you ask to transfer 
more than 2^55 logical blocks!).

scsi_req_enqueue returns an int32_t, so you cannot transfer more than 
31-bits per command right now, but you're right that resid is computed 
as size_t - int32_t and in principle could overflow the 32-bit value.

I plan to change all of this to 64-bit, but I'm not working too much on 
SCSI because I'd rather not inflict even more virtio-scsi rebase pain on 
myself.

Paolo