On 05/10/16 13:29, Jan Beulich wrote: >>>> On 05.10.16 at 14:22, <rcojoc...@bitdefender.com> wrote: >>> what's the point of this being used by hvmemul_read() and >>> hvmemul_cmpxchg(), but (namely but not limited to) not by >>> hvmemul_write()? >> To do introspection work, we sometimes need to modify the guest memory, >> and there are cases, namely during hibernate / resume of Windows guests, >> when we need to serve the "old" version of that memory to the current >> instruction reading from it for the process to work reliably. >> >> The design choice here has been that the introspection application is >> smart enough to handle writes (after all, it is the one managing the >> buffer sent via vm_event reply), so it is intended behaviour. > Well - the confusing thing is that for cmpxchg it's the value to be > written which gets altered, not the value to be compared against, > i.e. it acts as if set_context_data() was also intended to be > present in hvmemul_write().
Can I highly suggest that writing an Introspection feature doc, explaining some bits and pieces like this might be a very good idea? Also, commiseration to whichever poor sole had to debug that issue... ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
