Re: [PATCH kvmtool] aarch64: Give up with MTE for AArch32 guest

From: Alexandru Elisei <alexandru.elisei@arm.com>
To: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, will@kernel.org, maz@kernel.org
Subject: Re: [PATCH kvmtool] aarch64: Give up with MTE for AArch32 guest
Date: Fri, 20 May 2022 14:31:03 +0100	[thread overview]
Message-ID: <YoeYF/J2O/cLXmXZ@monolith.localdoman> (raw)
In-Reply-To: <20220520123844.127733-1-vladimir.murzin@arm.com>

Hi Vladimir,

When I run an --aarch32 guest with --debug this is the message that I'm
getting:

  Info: (arm/aarch64/kvm.c) kvm__arch_enable_mte:146: MTE capability not available

Would you mind elaborating on the merits of the message that you are
proposing:

  Info: (arm/aarch64/kvm.c) kvm__arch_enable_mte:124: MTE is incompatible with AArch32

Is it because it explains why the capability is not available?

Thanks,
Alex

On Fri, May 20, 2022 at 01:38:44PM +0100, Vladimir Murzin wrote:
> KVM doesn't support combination of MTE and AArch32 guest, so do not
> even try.
> 
> Signed-off-by: Vladimir Murzin <vladimir.murzin@arm.com>
> ---
>  arm/aarch64/kvm.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/arm/aarch64/kvm.c b/arm/aarch64/kvm.c
> index 1b992dd..f3fe854 100644
> --- a/arm/aarch64/kvm.c
> +++ b/arm/aarch64/kvm.c
> @@ -120,6 +120,11 @@ void kvm__arch_enable_mte(struct kvm *kvm)
>  		.cap = KVM_CAP_ARM_MTE,
>  	};
>  
> +	if (kvm->cfg.arch.aarch32_guest) {
> +		pr_debug("MTE is incompatible with AArch32");
> +		return;
> +	}
> +
>  	if (kvm->cfg.arch.mte_disabled) {
>  		pr_debug("MTE disabled by user");
>  		return;
> -- 
> 2.25.1
> 

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