linux-kernel - Re: [PATCH V1 3/6] xen/virtio: Add option to restrict memory access under Xen

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Date:   Mon, 25 Apr 2022 00:58:30 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Juergen Gross <jgross@...e.com>
Cc:     Oleksandr <olekstysh@...il.com>,
        Christoph Hellwig <hch@...radead.org>,
        xen-devel@...ts.xenproject.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Julien Grall <julien@....org>,
        Oleksandr Tyshchenko <oleksandr_tyshchenko@...m.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH V1 3/6] xen/virtio: Add option to restrict memory access
 under Xen

On Mon, Apr 25, 2022 at 09:47:49AM +0200, Juergen Gross wrote:
> > Would the Xen specific bits fit into Confidential Computing Platform
> > checks? I will let Juergen/Boris comment on this.
> 
> I don't think cc_platform_has would be correct here. Xen certainly
> provides more isolation between guests and dom0, but "Confidential
> Computing" is basically orthogonal to that feature.

The point of cc_platform_has is to remove all these open code checks.
If a Xen hypervisor / dom0 can't access arbitrary guest memory for
virtual I/O and we need special APIs for that it certainly false
into the scope of cc_platform_has, even if the confientiality is
rather limited.