Re: [RFC PATCH 0/5] Removing support for 32bit KVM/arm host

From: Marc Zyngier <maz@kernel.org>
To: Stefan Agner <stefan@agner.ch>
Cc: Vladimir Murzin <vladimir.murzin@arm.com>,
	Russell King <linux@arm.linux.org.uk>,
	kvm@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Quentin Perret <qperret@google.com>,
	Christoffer Dall <Christoffer.Dall@arm.com>,
	James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Will Deacon <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH 0/5] Removing support for 32bit KVM/arm host
Date: Thu, 20 Feb 2020 11:01:48 +0000	[thread overview]
Message-ID: <cbad8640f275b9beab471ddd3136da72@kernel.org> (raw)
In-Reply-To: <69845f739bbd91e73cd82e7c4683ab5a@agner.ch>

On 2020-02-19 13:53, Stefan Agner wrote:
> On 2020-02-10 15:13, Marc Zyngier wrote:
>> KVM/arm was merged just over 7 years ago, and has lived a very quiet
>> life so far. It mostly works if you're prepared to deal with its
>> limitations, it has been a good prototype for the arm64 version,
>> but it suffers a few problems:
>> 
>> - It is incomplete (no debug support, no PMU)
>> - It hasn't followed any of the architectural evolutions
>> - It has zero users (I don't count myself here)
>> - It is more and more getting in the way of new arm64 developments
>> 
>> So here it is: unless someone screams and shows that they rely on
>> KVM/arm to be maintained upsteam, I'll remove 32bit host support
>> form the tree. One of the reasons that makes me confident nobody is
>> using it is that I never receive *any* bug report. Yes, it is perfect.
> 
> Not entirely true:
> https://lore.kernel.org/m/e2f7196ca6c70c55463a45b490f6731a@agner.ch

And I thank you for that. This bug was actually hitting both arm and
arm64, and triggered by a bogus DT (that KVM should have handled in a
nicer way). What I was trying to say is that nobody reports bugs that
are specific to 32bit KVM/arm.

> But, after that was fixed, it actually was perfect :-D
> https://blog.printk.io/2016/09/kvm-with-kvmtool-on-armv7/

Hey, neat! not sure how useful, but neat nonetheless... ;-)

> That said, I never used it in a real-world application, so from my side
> removing it is fine.

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...

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