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From: Cornelia Huck <cohuck@redhat.com>
To: Jianyong Wu <jianyong.wu@arm.com>,
	maz@kernel.org, james.morse@arm.com, will@kernel.org
Cc: rmk@armlinux.org.uk, salil.mehta@huawei.com,
	suzuki.poulose@arm.com, oliver.upton@linux.dev,
	linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev,
	linux-kernel@vger.kernel.org, justin.he@arm.com,
	jianyong.wu@arm.com
Subject: Re: [PATCH] arm64/kvm: Introduce feature extension for SMCCC filter
Date: Thu, 16 Nov 2023 14:08:58 +0100	[thread overview]
Message-ID: <877cmhq1zp.fsf@redhat.com> (raw)
In-Reply-To: <20231116114152.912344-1-jianyong.wu@arm.com>

On Thu, Nov 16 2023, Jianyong Wu <jianyong.wu@arm.com> wrote:

> 821d935c87b introduces support for userspace SMCCC filtering, but lack
> of a way to tell userspace if we have this feature. Add a corresponding
> feature extension can resolve this issue.
>
> For example, the incoming feature Vcpu Hotplug needs the SMCCC filter.
> As there is no way to check this feature, VMM will run into error when
> it calls this feature on an old kernel. It's bad for backward compatible.

Can't you simply query via KVM_HAS_DEVICE_ATTR whether the SMCCC
filtering controls exist?

>
> Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
> ---
>  Documentation/virt/kvm/api.rst | 3 ++-
>  arch/arm64/kvm/arm.c           | 1 +
>  include/uapi/linux/kvm.h       | 1 +
>  3 files changed, 4 insertions(+), 1 deletion(-)
>


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  reply	other threads:[~2023-11-16 13:09 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-11-16 11:41 [PATCH] arm64/kvm: Introduce feature extension for SMCCC filter Jianyong Wu
2023-11-16 13:08 ` Cornelia Huck [this message]
2023-11-16 14:06   ` Salil Mehta
2023-11-21  1:58     ` Jianyong Wu
2023-11-16 14:21   ` Marc Zyngier
2023-11-21  2:01     ` Jianyong Wu
2023-11-16 19:06 ` Russell King (Oracle)
2023-11-16 23:22   ` Oliver Upton
2023-11-21 10:57     ` Salil Mehta

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