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Re: [PATCH v4 6/9] domain: map/unmap GADDR based shared guest areas
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Thu, 28 Sep 2023 13:10:35 +0200
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Henry Wang <Henry.Wang@xxxxxxx>
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- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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@xxxxxxxx>
> >
> > Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
>
> 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@xxxxxxxxxx>
Thanks, Roger.
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