From: Oliver Upton <oliver.upton@linux.dev>
To: Will Deacon <will@kernel.org>
Cc: kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH 1/2] KVM: arm64: Fix hvhe/nvhe early alias parsing
Date: Mon, 6 May 2024 17:35:38 +0000 [thread overview]
Message-ID: <ZjkU6qyd2IRcUi2M@linux.dev> (raw)
In-Reply-To: <20240502102030.GA16965@willie-the-truck>
On Thu, May 02, 2024 at 11:20:30AM +0100, Will Deacon wrote:
> Hey Oliver,
>
> On Wed, May 01, 2024 at 05:44:57PM +0000, Oliver Upton wrote:
> > On Wed, May 01, 2024 at 05:33:59PM +0100, Will Deacon wrote:
> > > Booting a kernel with "arm64_sw.hvhe=1 kvm-arm.mode=nvhe" on the
> > > command-line results in KVM initialising using hVHE, whereas one might
> > > expect the latter option to override the former.
> > >
> > > Fix this by adding "arm64_sw.hvhe=0" to the alias expansion for
> > > "kvm-arm.mode=nvhe".
> >
> > Hmm, I wonder if it'd be better to just evaluate the sanitised VH field
> > in hvhe_possible(). Otherwise I worry about keeping aliases in sync when
> > new command line options come along.
> >
> > This is similar to what we had before commit 35876f35f482 ("arm64:
> > cpufeature: Add helper to test for CPU feature overrides") w/ the added
> > use of the sanitised reg.
> >
> > Thoughts?
>
> I think that goes wonky when you have the arguments the other way around:
>
> "kvm-arm.mode=nvhe arm64_sw.hvhe=1"
>
> would end up using nVHE.
Right... What I was hoping to get at is a simple set of arguments to
test protected + nVHE, even on systems that support VHE. Although I
suppose:
"kvm-arm.mode=protected id_aa64mmfr1.vh=0 arm64_sw.hvhe=0"
isn't that bad and would preserve precedence of later args. So, FWIW:
Acked-by: Oliver Upton <oliver.upton@linux.dev>
--
Thanks,
Oliver
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next prev parent reply other threads:[~2024-05-06 17:36 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-01 16:33 [PATCH 0/2] Tweaks to the kvm-arm.mode= early cmdline parsing Will Deacon
2024-05-01 16:33 ` [PATCH 1/2] KVM: arm64: Fix hvhe/nvhe early alias parsing Will Deacon
2024-05-01 17:44 ` Oliver Upton
2024-05-02 10:20 ` Will Deacon
2024-05-06 17:35 ` Oliver Upton [this message]
2024-05-01 16:34 ` [PATCH 2/2] KVM: arm64: Use hVHE in pKVM by default on CPUs with VHE support Will Deacon
2024-05-01 17:47 ` Oliver Upton
2024-05-08 6:14 ` [PATCH 0/2] Tweaks to the kvm-arm.mode= early cmdline parsing Marc Zyngier
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