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Christopher Clark
4048189d01
The register op is used by a domain to register a region of memory for receiving messages from either a specified other domain, or, if specifying a wildcard, any domain. This operation creates a mapping within Xen's private address space that will remain resident for the lifetime of the ring. In subsequent commits, the hypervisor will use this mapping to copy data from a sending domain into this registered ring, making it accessible to the domain that registered the ring to receive data. Wildcard any-sender rings are default disabled and registration will be refused with EPERM unless they have been specifically enabled with the new mac-permissive flag that is added to the argo boot option here. The reason why the default for wildcard rings is 'deny' is that there is currently no means to protect the ring from DoS by a noisy domain spamming the ring, affecting other domains ability to send to it. This will be addressed with XSM policy controls in subsequent work. Since denying access to any-sender rings is a significant functional constraint, the new option "mac-permissive" for the argo bootparam enables overriding this. eg: "argo=1,mac-permissive=1" The p2m type of the memory supplied by the guest for the ring must be p2m_ram_rw and the memory will be pinned as PGT_writable_page while the ring is registered. This hypercall op and its interface currently only supports 4K-sized pages. Signed-off-by: Christopher Clark <christopher.clark6@baesystems.com> Tested-by: Chris Patterson <pattersonc@ainfosec.com> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com> Release-acked-by: Juergen Gross <jgross@suse.com>