Re: [GIT PULL] KVM/arm64 updates for 6.2

From: Marc Zyngier <maz@kernel.org>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: kvm@vger.kernel.org, "Catalin Marinas" <catalin.marinas@arm.com>,
	"Andrew Jones" <andrew.jones@linux.dev>,
	"Usama Arif" <usama.arif@bytedance.com>,
	"Bagas Sanjaya" <bagasdotme@gmail.com>,
	"Ben Gardon" <bgardon@google.com>,
	"Maciej S . Szmigiero" <maciej.szmigiero@oracle.com>,
	"Will Deacon" <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	"Marek Szyprowski" <m.szyprowski@samsung.com>,
	"Steven Price" <steven.price@arm.com>,
	linux-arm-kernel@lists.infradead.org,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Anshuman Khandual" <anshuman.khandual@arm.com>,
	"Arnaldo Carvalho de Melo" <acme@kernel.org>,
	"Mark Brown" <broonie@kernel.org>,
	kvmarm@lists.linux.dev, "Peter Collingbourne" <pcc@google.com>,
	"Philippe Mathieu-Daudé" <philmd@linaro.org>,
	"Cornelia Huck" <cohuck@redhat.com>,
	"Zhiyuan Dai" <daizhiyuan@phytium.com.cn>,
	"Andrew Morton" <akpm@linux-foundation.org>
Subject: Re: [GIT PULL] KVM/arm64 updates for 6.2
Date: Wed, 07 Dec 2022 07:49:08 +0000	[thread overview]
Message-ID: <877cz3u00b.wl-maz@kernel.org> (raw)
In-Reply-To: <28e7f298-972b-2cb8-df80-951076724c73@redhat.com>

On Tue, 06 Dec 2022 21:43:43 +0000,
Paolo Bonzini <pbonzini@redhat.com> wrote:
> 
> On 12/6/22 19:20, Mark Brown wrote:
> >> I almost suggested doing that on multiple occasions this cycle, but ultimately
> >> decided not to because it would effectively mean splitting series that touch KVM
> >> and selftests into different trees, which would create a different kind of
> >> dependency hell.  Or maybe a hybrid approach where series that only (or mostly?)
> >> touch selftests go into a dedicated tree?
> > 
> > Some other subsystems do have a separate branch for kselftests.  One
> > fairly common occurrence is that the selftests branch ends up failing to
> > build independently because someone adds new ABI together with a
> > selftest but the patches adding the ABI don't end up on the same branch
> > as the tests which try to use them.  That is of course resolvable but
> > it's a common friction point.
> 
> Yeah, the right solution is simply to merge selftests changes
> separately from the rest and use topic branches.

Don't know if this is what you have in mind, but I think that we
should use topic branches for *everything*. The only things for which
I don't use a separate branch are the odd drive-by patches, of the
spelling fix persuasion.

That's what we do for arm64 and the IRQ subsystem. It is a bit more
involved at queuing time, but makes dropping series from -next
extremely easy, without affecting the history. And crucially, it gives
everyone a hint to base their stuff on a stable commit, not a random
"tip of kvm/queue as of three days ago".

	M.

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