>>> On 14.01.15 at 11:31, <tamas.leng...@zentific.com> wrote: > On Wed, Jan 14, 2015 at 8:04 AM, Jan Beulich <jbeul...@suse.com> wrote: >>>>> Ed White <edmund.h.wh...@intel.com> 01/13/15 10:32 PM >>> >>>On 01/13/2015 12:45 PM, Andrew Cooper wrote: >>>> On 13/01/15 20:02, Ed White wrote: >>>>> The set of mfn's is the same, but I do allow gfn->mfn mappings to be >>>>> modified under certain circumstances. One use of this is to point the >>>>> same VA to different physical pages (with different access permissions) >>>>> in different p2m's to hide memory changes. >>>> >>>> What is the practical use of being able to play paging tricks like this >>>> behind a VMs back? >>> >>>I'm restricted in how much detail I can go into on a public mailing list, >>>but imagine that you want a data read to see one thing and an instruction >>>fetch to see something else. >> >> How would that work? There can only be one P2M in use at a time, and that's >> used for both translations. Or are you saying at least one of the two >> accesses >> would be emulated nevertheless? > > I can see it working by having data fetch access to a page trapped via > mem_access, while instruction fetch is not.
Understood, but how do you then carry out the data access? The question I raised was whether that would then involve emulation. Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
