From: Marc Zyngier <maz@kernel.org>
To: Alexander Graf <graf@amazon.com>
Cc: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH] KVM: arm64: Change default caching mode for {PEND, PROP}BASER.outer
Date: Sun, 05 Jul 2020 19:11:38 +0100 [thread overview]
Message-ID: <87o8otesrp.wl-maz@kernel.org> (raw)
In-Reply-To: <20200701140206.8664-1-graf@amazon.com>
On Wed, 01 Jul 2020 15:02:06 +0100,
Alexander Graf <graf@amazon.com> wrote:
>
> PENDBASER and PROPBASER define the outer caching mode for LPI tables.
> The memory backing them may not be outer sharable, so we mark them as nC
> by default. This however, breaks Windows on ARM which only accepts
> SameAsInner or RaWaWb as values for outer cachability.
>
> We do today already allow the outer mode to be set to SameAsInner
> explicitly, so the easy fix is to default to that instead of nC for
> situations when an OS asks for a not fulfillable cachability request.
>
> This fixes booting Windows in KVM with vgicv3 and ITS enabled for me.
>
> Signed-off-by: Alexander Graf <graf@amazon.com>
> ---
> arch/arm64/kvm/vgic/vgic-mmio-v3.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> index d2339a2b9fb9..5c786b915cd3 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> @@ -389,7 +389,7 @@ u64 vgic_sanitise_outer_cacheability(u64 field)
> case GIC_BASER_CACHE_nC:
> return field;
> default:
> - return GIC_BASER_CACHE_nC;
> + return GIC_BASER_CACHE_SameAsInner;
> }
> }
>
I am going to provisionally queue this for 5.9, with the explicit
reserve that it will be reverted if it causes a regression for other
guests (as this is an observable change in behaviour).
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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next prev parent reply other threads:[~2020-07-05 18:11 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-01 14:02 [PATCH] KVM: arm64: Change default caching mode for {PEND, PROP}BASER.outer Alexander Graf
2020-07-05 18:11 ` Marc Zyngier [this message]
2020-07-05 18:18 ` Marc Zyngier
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