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RE: For 4.17 (was: Re: [PATCH v3 0/2] Move calls to memory_type_changed())
- To: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxx>
- From: Henry Wang <Henry.Wang@xxxxxxx>
- Date: Thu, 29 Sep 2022 11:10:44 +0000
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Jun Nakajima <jun.nakajima@xxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Thu, 29 Sep 2022 11:11:19 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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- Thread-topic: For 4.17 (was: Re: [PATCH v3 0/2] Move calls to memory_type_changed())
Hi Roger and Jan,
> -----Original Message-----
> From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
> Subject: For 4.17 (was: Re: [PATCH v3 0/2] Move calls to
> memory_type_changed())
>
> On Thu, Sep 29, 2022 at 12:14:10PM +0200, Jan Beulich wrote:
> > On 28.09.2022 16:11, Roger Pau Monne wrote:
> > > The current calls to memory_type_changed() are wider than strictly
> > > necessary. Move them inside the iocap handlers and also limit to only
> > > issue them when required.
> > >
> > > I would really like to get some feedback on the Arm change, since this
> > > is now a prereq for the actual fix.
> > >
> > > Thanks, Roger.
> > >
> > > Roger Pau Monne (2):
> > > arm/vgic: drop const attribute from gic_iomem_deny_access()
> > > x86/ept: limit calls to memory_type_changed()
> >
> > Are there intentions for having these on 4.17?
>
> I wasn't sure. From XenServer PoV it's certainly a bug fix,
> otherwise some workloads related to GPU passthrough are simply too
> slow to be usable.
>
> I would certainly be fine with it making it's way into 4.17, let me
> add Henry:
>
> Cons:
> - Changes the number of issued memory_type_changed(), so there's a
> risk I misplaced some of the conditions and we end up with wrong
> cache types in the guest p2m due to missing memory_type_changed()
> calls. That however won't affect Xen itself, just the guest.
>
> Pros:
> - Removes unneeded memory_type_changed(), thus making some
> operations
> faster. It's effect it's greatly dependent on using a set of
> hypercalls against a domain, which doesn't seem common in upstream.
> It's possible other products based on Xen apart from XenServer will
> also see an speedup as a result.
Thanks for the information and the detailed summary!
I think my understanding is the same as what Jan has in
"x86/NUMA: correct memnode_shift calculation for single node system",
- we are still not in code freeze but in feature freeze, so properly-reviewed
fixes are eligible for the release. For this specific series, (to me) it looks
ok
and I will not block the merging of this series if maintainers want to merge
it :))
Kind regards,
Henry
>
> Thanks, Roger.
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