Re: [Qemu-arm] [Qemu-devel] [PATCH for-4.0?] arm: Allow system registers for KVM guests to be changed by QEMU code

[Peter Maydell]

On Mon, 18 Mar 2019 at 12:34, gengdongjiu <address@hidden> wrote:
>
>
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> On 2019/3/16 4:11, Philippe Mathieu-Daudé wrote:
> >> Signed-off-by: Peter Maydell <address@hidden>
> >> ---
> >> Should we try to put this in for rc1? Not sure... Testing
> >> definitely appreciated.
> > You might include it for rc1 and we still have rc2/rc3 to revert it.
>
> why we still have rc2/rc3 to revert it?

I think Philippe's point is that it's reasonably safe to
apply this patch in rc1 (ie now), because if we do do that
and then discover that we have some other bug in it, we
still have plenty of time to take the patch out again
before release.

(If we did discover another bug in this patch in future, I
would favour reverting it for the 4.0 release rather than
trying to fix whatever that bug was, because two unexpected
bugs in the patch means I clearly didn't understand
the code well enough to produce a reliable patch. The cases
that this patch fixes are pretty rare -- it does fix a bug
but only in handling of some cases of debugging a KVM guest;
but the patch potentially affects the behaviour of any
KVM guest, even if the user isn't trying to debug. So it's
riskier than some other kinds of change, and on balance
that means that when we're making a decision at rc2 or rc3
I'm more in favour of just reverting it rather than
applying what we hope is a fix.)

thanks
-- PMM