On Fri, Apr 27, 2018 at 02:02:46PM +0100, Stefan Hajnoczi wrote: > On Wed, Apr 25, 2018 at 04:23:12PM +0800, Tiwei Bie wrote: > > There will be hardware virtio devices in the future, which > > require drivers to use the barriers suitable for I/O device, > > compared with software virtio devices which just require > > drivers to use the barriers suitable for CPU core. > > > > To fix the ordering issue for hardware virtio devices, add > > a new feature: VIRTIO_F_IO_BARRIER. When negotiated, driver > > will use the barriers suitable for I/O device. > > > > Signed-off-by: Tiwei Bie <[email protected]> > > --- > > content.tex | 9 +++++++++ > > 1 file changed, 9 insertions(+) > > > > diff --git a/content.tex b/content.tex > > index ae5fa4c..f24e320 100644 > > --- a/content.tex > > +++ b/content.tex > > @@ -5445,6 +5445,8 @@ Descriptors} and \ref{sec:Packed Virtqueues / > > Indirect Flag: Scatter-Gather Supp > > that drivers pass extra data (besides identifying the Virtqueue) > > in their device notifications. > > See \ref{sec:Virtqueues / Driver notifications}~\nameref{sec:Virtqueues > > / Driver notifications}. > > + \item[VIRTIO_F_IO_BARRIER(37)] This feature indicates that the device > > + needs the driver to use the barriers suitable for hardware device. > > s/hardware device/hardware devices/ (plural) > > > \end{description} > > > > \drivernormative{\section}{Reserved Feature Bits}{Reserved Feature Bits} > > @@ -5460,6 +5462,10 @@ addresses to the device. > > > > A driver SHOULD accept VIRTIO_F_RING_PACKED if it is offered. > > > > +A driver SHOULD accept VIRTIO_F_IO_BARRIER if it is offered. > > +If VIRTIO_F_IO_BARRIER has been negotiated, a driver MUST use > > +the barriers suitable for hardware device. > > s/hardware device/hardware devices/ (plural) > > Please add a little context so the purpose is clear to readers (I > wouldn't be 100% sure what the spec means without more detail): > > Some transports require barriers to ensure hardware devices have a > consistent view of memory. When devices are implemented in software a > weaker form of barrier may be sufficient and yield better performance. > This feature bit indicates whether the full hardware barrier is > necessary.
Thank you very much for the review and suggestion! :) Best regards, Tiwei Bie --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
