Re: [Qemu-devel] [PATCH 04/19] libqos/ahci: Add command header helpers

[John Snow]

On 02/02/2015 05:27 AM, Paolo Bonzini wrote:
> On 30/01/2015 19:41, John Snow wrote:
> > +/* Set the #cx'th command of port #px. */
> > +void ahci_set_command_header(AHCIQState *ahci, uint8_t px,
> > +                             uint8_t cx, AHCICommandHeader *cmd)
> > +{
> > +    uint64_t ba = ahci->port[px].clb;
> > +    ba += cx * sizeof(AHCICommandHeader);
> > +
> > +    cmd->flags = cpu_to_le16(cmd->flags);
> > +    cmd->prdtl = cpu_to_le16(cmd->prdtl);
> > +    cmd->prdbc = cpu_to_le32(cmd->prdbc);
> > +    cmd->ctba = cpu_to_le64(cmd->ctba);
>
> Modifying cmd is uglyish, and especially it might hide bugs that only
> happen on big endian system.  Please copy to a local AHCICommandHeader
> variable before adjusting for host endianness.
>
> Paolo
>
> > +    memwrite(ba, cmd, sizeof(AHCICommandHeader));
> > +}

You're right. I had just never actually thought to reference the command 
after committing it before, so I hadn't considered it in that light.

If I intend to share goodies with other tests it would be nice if they 
didn't do secretly evil things :)