Re: [PATCH v4 6/9] domain: map/unmap GADDR based shared guest areas

["Roger Pau Monné" <roger.pau@citrix.com>]

On Thu, Sep 28, 2023 at 12:14:17PM +0200, Jan Beulich wrote:
> On 28.09.2023 12:04, Roger Pau Monné wrote:
> > On Thu, Sep 28, 2023 at 09:16:48AM +0200, Jan Beulich wrote:
> >> The registration by virtual/linear address has downsides: At least on
> >> x86 the access is expensive for HVM/PVH domains. Furthermore for 64-bit
> >> PV domains the areas are inaccessible (and hence cannot be updated by
> >> Xen) when in guest-user mode, and for HVM guests they may be
> >> inaccessible when Meltdown mitigations are in place. (There are yet
> >> more issues.)
> >>
> >> In preparation of the introduction of new vCPU operations allowing to
> >> register the respective areas (one of the two is x86-specific) by
> >> guest-physical address, flesh out the map/unmap functions.
> >>
> >> Noteworthy differences from map_vcpu_info():
> >> - areas can be registered more than once (and de-registered),
> >> - remote vCPU-s are paused rather than checked for being down (which in
> >>   principle can change right after the check),
> >> - the domain lock is taken for a much smaller region.
> >>
> >> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> > 
> > Acked-by: Roger Pau Monné <roger.pau@citrix.com>
> 
> Thanks, but to be clear: Formally this doesn't help this patch make any
> progress, aiui. I'll still need an A-b by a REST maintainer then. An R-b
> from you would be different in this regard.

I see.

Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>

Thanks, Roger.