> -----Original Message----- > From: Jan Beulich [mailto:jbeul...@suse.com] > Sent: 25 June 2015 14:48 > To: Paul Durrant > Cc: Andrew Cooper; xen-de...@lists.xenproject.org; Keir (Xen.org) > Subject: RE: [PATCH v4 07/17] x86/hvm: add length to mmio check op > > >>> On 25.06.15 at 15:36, <paul.durr...@citrix.com> wrote: > > I think that also allows me to simplfy the patch since I don't have to > > modify the mmio_check op any more. I simply call it once for the first byte > > of the access and, if it accepts, verify that it also accepts the last byte > > of the access. > > That's actually not (generally) okay: There could be a hole in the > middle. But as long as instructions don't do accesses wider than > a page, we're fine with that in practice I think. Or wait, no, in the > MSI-X this could not be okay: A 64-byte read to the 16 bytes > 32 bytes away from a page boundary (and being the last entry > on one device's MSI-X table) would extend into another device's > MSI-X table on the next page. I.e. first and last bytes would be > okay to be accessed, but bytes 16...31 of the access wouldn't. > Of course the MSI-X read/write handlers don't currently permit > such wide accesses, but anyway... >
We could also verify that, for a rep op, all reads/writes come back with OKAY. I think that would be ok. Paul > Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
