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

From: Juergen Gross
Date: Mon Apr 25 2022 - 03:48:49 EST

On 24.04.22 18:53, Oleksandr wrote:

On 23.04.22 19:40, Christoph Hellwig wrote:

Hello Christoph

Please split this into one patch that creates grant-dma-ops, and another
that sets up the virtio restricted access helpers.

Sounds reasonable, will do:

1. grant-dma-ops.c with config XEN_GRANT_DMA_OPS

2. arch_has_restricted_virtio_memory_access() with config XEN_VIRTIO

+int arch_has_restricted_virtio_memory_access(void)
+    return (xen_has_restricted_virtio_memory_access() ||
+            cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT));
So instead of hardcoding Xen here, this seems like a candidate for
another cc_platform_has flag.

I have a limited knowledge of x86 and Xen on x86.

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.


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