From: Vincent Donnefort <vdonnefort@google.com>
To: Marc Zyngier <maz@kernel.org>
Cc: Oliver Upton <oliver.upton@linux.dev>,
kvmarm@lists.cs.columbia.edu, kvmarm@lists.linux.dev,
kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Quentin Perret <qperret@google.com>,
Will Deacon <will@kernel.org>
Subject: Re: [PATCH] KVM: arm64: pkvm: Fixup boot mode to reflect that the kernel resumes from EL1
Date: Thu, 13 Oct 2022 14:33:38 +0100 [thread overview]
Message-ID: <Y0gTshQFSTwh+Eqf@google.com> (raw)
In-Reply-To: <87pmeygjrl.wl-maz@kernel.org>
On Tue, Oct 11, 2022 at 09:58:22PM +0100, Marc Zyngier wrote:
> On Tue, 11 Oct 2022 19:48:39 +0100,
> Oliver Upton <oliver.upton@linux.dev> wrote:
> >
> > On Tue, Oct 11, 2022 at 05:54:00PM +0100, Marc Zyngier wrote:
> > > The kernel has an awfully complicated boot sequence in order to cope
> > > with the various EL2 configurations, including those that "enhanced"
> > > the architecture. We go from EL2 to EL1, then back to EL2, staying
> > > at EL2 if VHE capable and otherwise go back to EL1.
> > >
> > > Here's a paracetamol tablet for you.
> >
> > Heh, still have a bit of a headache from this :)
> >
> > I'm having a hard time following where we skip the EL2 promotion based
> > on __boot_cpu_mode.
> >
> > On the cpu_resume() path it looks like we take the return of
> > init_kernel_el() and pass that along to finalise_el2(). As we are in EL1
> > at this point, it seems like we'd go init_kernel_el() -> init_el1().
> >
> > What am I missing?
>
> That I'm an idiot.
>
> This is only necessary on pre-6.0, before 005e12676af0 ("arm64: head:
> record CPU boot mode after enabling the MMU"), as this code-path
> *used* to reload the boot mode from memory. Now, this is directly
> passed as a parameter, making this patch useless.
On a 5.10 though, the suprious HVCs are gone and I have not observed any
regression.
Thanks!
For a stable fix:
Tested-by: Vincent Donnefort <vdonnefort@google.com>
>
> The joys of looking at too many code bases at the same time... I'll
> see how we can add it to 5.19.
>
> Thanks,
>
> M.
>
> --
> Without deviation from the norm, progress is not possible.
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prev parent reply other threads:[~2022-10-13 13:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-11 16:54 [PATCH] KVM: arm64: pkvm: Fixup boot mode to reflect that the kernel resumes from EL1 Marc Zyngier
2022-10-11 18:48 ` Oliver Upton
2022-10-11 20:58 ` Marc Zyngier
2022-10-13 13:33 ` Vincent Donnefort [this message]
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