linux-kernel - Re: [PATCH v3 1/1] KVM: arm64: Allow cacheable stage 2 mapping using VMA flags

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Message-ID: <20250318125751.GQ9311@nvidia.com>
Date: Tue, 18 Mar 2025 09:57:51 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Marc Zyngier <maz@...nel.org>
Cc: ankita@...dia.com, oliver.upton@...ux.dev, joey.gouly@....com,
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Subject: Re: [PATCH v3 1/1] KVM: arm64: Allow cacheable stage 2 mapping using
 VMA flags

On Mon, Mar 10, 2025 at 11:54:52AM +0000, Marc Zyngier wrote:

> Which brings me to the next point: FWB is not discoverable from
> userspace. How do you expect a VMM to know what it can or cannot do?

If you add a check at memslot creation time then simply fail the
memslot.

There is nothing the VMM can do except completely fail. There is no
alternative path here where a cachable VMA can be safely made
non-cachable for the guest?

Jason