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Message-ID: <874jdu9vjr.wl-maz@kernel.org>
Date: Tue, 27 Feb 2024 08:10:48 +0000
From: Marc Zyngier <maz@...nel.org>
To: Wei-Lin Chang <r09922117@...e.ntu.edu.tw>
Cc: oliver.upton@...ux.dev,
james.morse@....com,
suzuki.poulose@....com,
yuzenghui@...wei.com,
catalin.marinas@....com,
will@...nel.org,
linux-arm-kernel@...ts.infradead.org,
kvmarm@...ts.linux.dev,
linux-kernel@...r.kernel.org,
sauravsc@...zon.com,
eric.auger@...hat.com
Subject: Re: [PATCH 1/1] KVM: arm64: Affinity level 3 support
On Tue, 27 Feb 2024 02:27:08 +0000,
Wei-Lin Chang <r09922117@...e.ntu.edu.tw> wrote:
>
> On Sun, 25 Feb 2024 11:19:05 +0000,
> Marc Zyngier <maz@...nel.org> wrote:
[...]
> > I can see multiple problems with this:
> >
> > - this is the host state, which shouldn't necessarily represent the
> > guest state. It should be possible to restore a VM that have a
> > different A3V value and still have the same guarantees. There is
> > however a small nit around ICV_CTLR_EL1.A3V, which would require
> > trapping to emulate the A3V bit.
> >
> > - this assumes GICv3, which is definitely not universal (we support
> > GICv2, for which no such restriction actually exists).
> >
> > Finally, I don't see VM save/restore being addressed here, and I
> > suspect it hasn't been looked at.
> >
> > Overall, this patch does too many things, and it should be split in
> > discrete changes. I also want to see an actual justification for Aff3
> > support. And if we introduce it, it must be fully virtualised
> > (independent of the A3V support on the host).
>
> Hi Marc,
>
> Really appreciate for the feedback. I think I understand most of your
> comments and agree with them. It appears that I don't fully understand
> the changes that I am doing with this. Thanks for explaining.
I hope this doesn't deter you from working on this feature. I'll
happily answer questions and discuss the above points.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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