From: Marc Zyngier <maz@kernel.org>
To: Shenming Lu <lushenming@huawei.com>
Cc: Eric Auger <eric.auger@redhat.com>, Will Deacon <will@kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<kvmarm@lists.cs.columbia.edu>, <kvm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>,
Alex Williamson <alex.williamson@redhat.com>,
Cornelia Huck <cohuck@redhat.com>,
"Lorenzo\ Pieralisi" <lorenzo.pieralisi@arm.com>,
<wanghaibin.wang@huawei.com>, <yuzenghui@huawei.com>
Subject: Re: [PATCH v3 2/4] KVM: arm64: GICv4.1: Try to save hw pending state in save_pending_tables
Date: Fri, 12 Mar 2021 09:02:58 +0000 [thread overview]
Message-ID: <87lfasg2wt.wl-maz@kernel.org> (raw)
In-Reply-To: <3b47598f-0795-a165-1a64-abe02258b306@huawei.com>
On Thu, 11 Mar 2021 12:31:48 +0000,
Shenming Lu <lushenming@huawei.com> wrote:
>
> On 2021/3/11 17:09, Marc Zyngier wrote:
> > I have asked that question in the past: is it actually safe to remap
> > the vPEs and expect them to be runnable
>
> In my opinion, logically it can work, but there might be problems like the
> one below that I didn't notice...
One thing is that you will have lost interrupts in the meantime
(assuming your devices are still alive). How will you make up for
that?
>
> >
> > Also, the current code assumes that VMAPP.PTZ can be advertised if a
> > VPT is mapped for the first time. Clearly, it is unlikely that the VPT
> > will be only populated with 0s, so you'll end up with state corruption
> > on the first remap.
>
> Oh, thanks for pointing it out.
> And if we always signal PTZ when alloc = 1, does it mean that we
> can't remap the vPE when the VPT is not empty, thus there is no
> chance to get the VLPI state? Could we just assume that the VPT is
> not empty when first mapping the vPE?
I think we should drop the setting of PTZ altogether. It is a silly
micro-optimisation, and if the HW can't parse the VPT efficiently when
it is empty, then the HW is pretty bad, PTZ or not.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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next prev parent reply other threads:[~2021-03-12 9:04 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-27 12:13 [PATCH v3 0/4] KVM: arm64: Add VLPI migration support on GICv4.1 Shenming Lu
2021-01-27 12:13 ` [PATCH v3 1/4] KVM: arm64: GICv4.1: Add function to get VLPI state Shenming Lu
2021-03-11 8:57 ` Marc Zyngier
2021-03-11 12:26 ` Shenming Lu
2021-03-12 8:52 ` Marc Zyngier
2021-01-27 12:13 ` [PATCH v3 2/4] KVM: arm64: GICv4.1: Try to save hw pending state in save_pending_tables Shenming Lu
2021-03-11 9:09 ` Marc Zyngier
2021-03-11 12:31 ` Shenming Lu
2021-03-12 9:02 ` Marc Zyngier [this message]
2021-03-12 10:47 ` Shenming Lu
2021-01-27 12:13 ` [PATCH v3 3/4] KVM: arm64: GICv4.1: Restore VLPI's pending state to physical side Shenming Lu
2021-03-11 9:14 ` Marc Zyngier
2021-03-11 12:32 ` Shenming Lu
2021-03-12 9:05 ` Marc Zyngier
2021-03-12 10:48 ` Shenming Lu
2021-03-12 11:10 ` Marc Zyngier
2021-03-12 11:34 ` Shenming Lu
2021-03-12 12:02 ` Marc Zyngier
2021-03-12 12:31 ` Shenming Lu
2021-01-27 12:13 ` [PATCH v3 4/4] KVM: arm64: GICv4.1: Give a chance to save VLPI's pending state Shenming Lu
2021-02-26 8:58 ` [PATCH v3 0/4] KVM: arm64: Add VLPI migration support on GICv4.1 Shenming Lu
2021-03-11 7:03 ` Shenming Lu
2021-03-11 9:17 ` Marc Zyngier
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