Re: [Qemu-devel] [PATCH] nvme: fix copy direction in DMA reads going to CMB

[Klaus Birkelund <klaus@birkelund.eu>]

On Mon, May 20, 2019 at 09:05:57AM -0600, Keith Busch wrote:
> On Sat, May 18, 2019 at 09:39:05AM +0200, Klaus Birkelund Jensen wrote:
> > `nvme_dma_read_prp` erronously used `qemu_iovec_*to*_buf` instead of
> > `qemu_iovec_*from*_buf` when the request involved the controller memory
> > buffer.
> > 
> > Signed-off-by: Klaus Birkelund Jensen <klaus.jensen@cnexlabs.com>
> 
> I was wondering how this mistake got by for so long, and it looks like
> the only paths here require an admin command with dev->host transfer
> to CMB. That's just not done in any host implementation I'm aware of
> since it'd make it more difficult to use for no particular gain AFAICS,
> so I'd be curious to hear if you have a legit implementation doing this.
> 

I'm just trying to get the device to be as compliant as possible, but I
don't know why you'd have any reason to do a, say Get Feature, to the
CMB.