[virtio-comment] Re: [PATCH V2 6/6] virtio-pci: implement dirty page tracking

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Nov 06, 2023 at 11:21:12AM +0000, Parav Pandit wrote:
> 
> > From: Michael S. Tsirkin <mst@redhat.com>
> > Sent: Monday, November 6, 2023 4:00 PM
> > 
> > On Mon, Nov 06, 2023 at 04:34:44AM +0000, Parav Pandit wrote:
> > > > Do you know there are locked transaction and atomic operations in PCI???
> > > Can you explain how PCI does RMW locked transaction?
> > > Is it one TLP or multiple?
> > 
> > Parav what are you asking about here? 
> 
> > pcie supports CAS and Swap which likely
> > can work for this use-case - these are non posted writes. It's in the pcie spec.
> PCI spec do not have atomic OR operation.
> Lingshan in above comment suggested some unknown locked transaction and atomic operation.
> So I was asking him which is that atomic operation and how PCI does it?
> I don't know if any that can do PCI atomic OR without a workaround.

Well this is not what you wrote - you asked about RMW and that's exactly what CAS does.
Maybe you should take a bit more care writing then. Generally this
discussion would benefit a lot if people stop shooting from the hip.

-- 
MST


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