Re: [Xen-devel] memaccess: skipping mem_access_send_req

[Gareth Stockwell <Gareth.Stockwell@xxxxxxx>]

On Fri, Apr 10, 2015 at 17:03:26, Andrew Cooper wrote:
> Are you perhaps looking for something similar to Intel #VE support?
Yes, in that we want a way to notify a guest that it has made an access that 
violated a stage-2 / EPT permission.  However, for our purposes a trap into the 
hypervisor followed by injection of a virtual interrupt into the guest is 
acceptable; we don't require the interrupt to be directly delivered to the 
guest.

> (although I guess you are looking at ARM rather than x86)
Yes, my email address is a giveaway ;)

> It is not safe to always re-inject back into the vcpu, especially if
> the permission changes were around the guest kernel stack, but a
> restricted subset ought to be safe to bounce straight in.
The permission changes will be applied only to DMA buffers, rather than to 
anything the guest kernel itself needs to touch - so should be safe to directly 
re-inject.


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