> -----Original Message----- > From: Jan Beulich [mailto:jbeul...@suse.com] > Sent: 25 June 2015 15:46 > 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 15:52, <paul.durr...@citrix.com> wrote: > >> -----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. > > I wasn't thinking of a rep op, but of an AVX-512 memory access. >
That's ok because it would be chunked at the higher level and accept() would be called for each (up to) 8 byte chunk. Paul > Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
