Re: [Qemu-devel] [PATCH 10/16] scsi: move request parsing to common code

[Paolo Bonzini]

On 08/12/2011 06:55 PM, Peter Maydell wrote:
> Does it still make sense to set req->cmd to cmd (and to look at cmd
> at all) in the case where scsi_req_parse() failed and might not have
> actually initialised all of cmd? For instance the tracing code (added
> to scsi_req_new() after this patch) looks at cmd.buf[] based on the
> value of buf[0], which seems kind of fragile to me.

At the point tracing is reached, we know that cmd.buf[] has been 
initialized.  But you're right that it is at least not tidy.

We know that the size of the cdb is 16 (it is always like that, and we 
can make it a requirement).  So we can copy it to cmd->buf before 
knowing cmd->len, at the beginning of scsi_req_parse.  We can also zero 
unconditionally len/xfer/mode (plus set lba to -1) in case the parsing 
fails.

Paolo