linux-kernel - Re: [PATCH v13 11/40] arm64/gcs: Provide basic EL2 setup to allow GCS usage at EL0 and EL1

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Message-ID: <Zw1Hc38CwFS2XE6c@arm.com>
Date: Mon, 14 Oct 2024 17:31:47 +0100
From: Catalin Marinas <catalin.marinas@....com>
To: Marc Zyngier <maz@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>, Mark Brown <broonie@...nel.org>,
	Will Deacon <will@...nel.org>, Jonathan Corbet <corbet@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	James Morse <james.morse@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Arnd Bergmann <arnd@...db.de>, Oleg Nesterov <oleg@...hat.com>,
	Eric Biederman <ebiederm@...ssion.com>,
	Shuah Khan <shuah@...nel.org>,
	"Rick P. Edgecombe" <rick.p.edgecombe@...el.com>,
	Deepak Gupta <debug@...osinc.com>, Ard Biesheuvel <ardb@...nel.org>,
	Szabolcs Nagy <Szabolcs.Nagy@....com>, Kees Cook <kees@...nel.org>,
	"H.J. Lu" <hjl.tools@...il.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Florian Weimer <fweimer@...hat.com>,
	Christian Brauner <brauner@...nel.org>,
	Thiago Jung Bauermann <thiago.bauermann@...aro.org>,
	Ross Burton <ross.burton@....com>,
	David Spickett <david.spickett@....com>,
	Yury Khrustalev <yury.khrustalev@....com>,
	Wilco Dijkstra <wilco.dijkstra@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-doc@...r.kernel.org,
	kvmarm@...ts.linux.dev, linux-fsdevel@...r.kernel.org,
	linux-arch@...r.kernel.org, linux-mm@...ck.org,
	linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v13 11/40] arm64/gcs: Provide basic EL2 setup to allow
 GCS usage at EL0 and EL1

On Fri, Oct 11, 2024 at 01:55:05PM +0100, Marc Zyngier wrote:
> On Thu, 10 Oct 2024 18:16:52 +0100,
> Catalin Marinas <catalin.marinas@....com> wrote:
> > 
> > On Thu, Oct 10, 2024 at 04:18:13PM +0100, Marc Zyngier wrote:
> > > From 20c98d2647c11db1e40768f92c5998ff5d764a3a Mon Sep 17 00:00:00 2001
> > > From: Marc Zyngier <maz@...nel.org>
> > > Date: Thu, 10 Oct 2024 16:13:26 +0100
> > > Subject: [PATCH] KVM: arm64: Shave a few bytes from the EL2 idmap code
> > > 
> > > Our idmap is becoming too big, to the point where it doesn't fit in
> > > a 4kB page anymore.
> > > 
> > > There are some low-hanging fruits though, such as the el2_init_state
> > > horror that is expanded 3 times in the kernel. Let's at least limit
> > > ourselves to two copies, which makes the kernel link again.
> > > 
> > > At some point, we'll have to have a better way of doing this.
> > > 
> > > Reported-by: Nathan Chancellor <nathan@...nel.org>
> > > Signed-off-by: Marc Zyngier <maz@...nel.org>
> > > Link: https://lore.kernel.org/r/20241009204903.GA3353168@thelio-3990X
> > 
> > Thanks Marc for the quick fix. It looks fine to me, it will keep the
> > linker quiet for a while. I pushed it to arm64 for-kernelci for the time
> > being, see if anything falls apart. I'll apply it properly once it gets
> > a bit more testing.
> 
> Works for me. But if that helps, I can also queue it as a KVM fix for
> 6.12, leaving the GCS branch unencumbered. Just let me know.

That would help, thanks. The for-kernelci branch merges the latest mainline
rc anyway, so it will no longer blow up allmodconfig tests.

-- 
Catalin