linux-kernel - Re: [PATCH vhost v4 02/15] vdpa: Add VHOST_BACKEND_F_CHANGEABLE_VQ_ADDR_IN

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Message-ID: <a67c3ee375b1ae4aac5cc39539e1a25e23bf4f07.camel@nvidia.com>
Date: Fri, 22 Dec 2023 10:51:13 +0000
From: Dragos Tatulea <dtatulea@...dia.com>
To: "mst@...hat.com" <mst@...hat.com>
CC: "xuanzhuo@...ux.alibaba.com" <xuanzhuo@...ux.alibaba.com>, Parav Pandit
	<parav@...dia.com>, Gal Pressman <gal@...dia.com>,
	"virtualization@...ts.linux-foundation.org"
	<virtualization@...ts.linux-foundation.org>, "eperezma@...hat.com"
	<eperezma@...hat.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "si-wei.liu@...cle.com"
	<si-wei.liu@...cle.com>, "jasowang@...hat.com" <jasowang@...hat.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>, Saeed Mahameed
	<saeedm@...dia.com>, "leon@...nel.org" <leon@...nel.org>
Subject: Re: [PATCH vhost v4 02/15] vdpa: Add
 VHOST_BACKEND_F_CHANGEABLE_VQ_ADDR_IN_SUSPEND flag

On Fri, 2023-12-22 at 03:29 -0500, Michael S. Tsirkin wrote:
> On Thu, Dec 21, 2023 at 03:07:22PM +0000, Dragos Tatulea wrote:
> > > > > In that case you're right, we don't need feature flags. But I think it
> > > > > would be great to also move the error return in case userspace tries
> > > > > to modify vq parameters out of suspend state.
> > > > > 
> > > > On the driver side or on the core side?
> > > > 
> > > 
> > > Core side.
> > > 
> > Checking my understanding: instead of the feature flags there would be a check
> > (for .set_vq_addr and .set_vq_state) to return an error if they are called under
> > DRIVER_OK and not suspended state?
> 
> Yea this looks much saner, if we start adding feature flags for
> each OPERATION_X_LEGAL_IN_STATE_Y then we will end up with N^2
> feature bits which is not reasonable.
> 
Ack. Is the v2 enough or should I respin a v5 with the updated Acked-by tags?

I will prepare the core part as a different series without the flags.

Thanks,
Dragos