Re: [PATCH v11 00/43] KVM: arm64: Nested Virtualization support (FEAT_NV2 only)

From: Marc Zyngier <maz@kernel.org>
To: Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com>
Cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Alexandru Elisei <alexandru.elisei@arm.com>,
	Andre Przywara <andre.przywara@arm.com>,
	Chase Conklin <chase.conklin@arm.com>,
	Christoffer Dall <christoffer.dall@arm.com>,
	Darren Hart <darren@os.amperecomputing.com>,
	Jintack Lim <jintack@cs.columbia.edu>,
	Russell King <rmk+kernel@armlinux.org.uk>,
	Miguel Luis <miguel.luis@oracle.com>,
	James Morse <james.morse@arm.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Oliver Upton <oliver.upton@linux.dev>,
	Zenghui Yu <yuzenghui@huawei.com>
Subject: Re: [PATCH v11 00/43] KVM: arm64: Nested Virtualization support (FEAT_NV2 only)
Date: Tue, 21 Nov 2023 09:08:55 +0000	[thread overview]
Message-ID: <86ttpfzd5k.wl-maz@kernel.org> (raw)
In-Reply-To: <a44660c4-e43a-4663-94c0-9b290ea755e3@os.amperecomputing.com>

On Tue, 21 Nov 2023 08:51:35 +0000,
Ganapatrao Kulkarni <gankulkarni@os.amperecomputing.com> wrote:
> 
> 
> Hi Marc,
> 
> On 20-11-2023 06:39 pm, Marc Zyngier wrote:
> > This is the 5th drop of NV support on arm64 for this year, and most
> > probably the last one for this side of Christmas.
> > 
> > For the previous episodes, see [1].
> > 
> > What's changed:
> > 
> > - Drop support for the original FEAT_NV. No existing hardware supports
> >    it without FEAT_NV2, and the architecture is deprecating the former
> >    entirely. This results in fewer patches, and a slightly simpler
> >    model overall.
> > 
> > - Reorganise the series to make it a bit more logical now that FEAT_NV
> >    is gone.
> > 
> > - Apply the NV idreg restrictions on VM first run rather than on each
> >    access.
> > 
> > - Make the nested vgic shadow CPU interface a per-CPU structure rather
> >    than per-vcpu.
> > 
> > - Fix the EL0 timer fastpath
> > 
> > - Work around the architecture deficiencies when trapping WFI from a
> >    L2 guest.
> > 
> > - Fix sampling of nested vgic state (MISR, ELRSR, EISR)
> > 
> > - Drop the patches that have already been merged (NV trap forwarding,
> >    per-MMU VTCR)
> > 
> > - Rebased on top of 6.7-rc2 + the FEAT_E2H0 support [2].
> > 
> > The branch containing these patches (and more) is at [3]. As for the
> > previous rounds, my intention is to take a prefix of this series into
> > 6.8, provided that it gets enough reviewing.
> > 
> > [1] https://lore.kernel.org/r/20230515173103.1017669-1-maz@kernel.org
> > [2] https://lore.kernel.org/r/20231120123721.851738-1-maz@kernel.org
> > [3] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/log/?h=kvm-arm64/nv-6.8-nv2-only
> > 
> 
> V11 series is not booting on Ampere platform (I am yet to debug).
> With lkvm, it is stuck at the very early stage itself and no early
> boot prints/logs.
> 
> Are there any changes needed in kvmtool for V11?

Not really, I'm still using the version I had built for 6.5. Is the
problem with L1 or L2?

However, this looks like a problem I've been chasing, and which I
though was only a M2 issue. In some situations, I'm getting interrupt
storms when L1 gets a level interrupt while in L2.

Can you cherry-pick [1] from my tree, and let me know if this helps?
This isn't a proper fix, but if L2 starts booting with this, I would
know this is a common issue.

Now, if your problem is with L1, I really have no idea.

Thanks,

	M.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=kvm-arm64/nv-6.8-nv2-only&id=759d2e18f8954f4c76eb1772f38301df6ed8fa5d

-- 
Without deviation from the norm, progress is not possible.

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