> -----Original Message----- > From: Jan Beulich [mailto:jbeul...@suse.com] > Sent: 13 January 2017 10:31 > To: Andrew Cooper <andrew.coop...@citrix.com>; Paul Durrant > <paul.durr...@citrix.com> > Cc: Ian Jackson <ian.jack...@citrix.com>; Jennifer Herbert > <jennifer.herb...@citrix.com>; Wei Liu <wei.l...@citrix.com>; xen- > de...@lists.xenproject.org; Daniel DeGraaf <dgde...@tycho.nsa.gov> > Subject: RE: [PATCH v3 1/8] public / x86: Introduce __HYPERCALL_dm_op... > > >>> On 13.01.17 at 10:05, <paul.durr...@citrix.com> wrote: > >> From: Jan Beulich [mailto:jbeul...@suse.com] > >> Sent: 12 January 2017 16:29 > >> >>> On 12.01.17 at 17:10, <paul.durr...@citrix.com> wrote: > >> >> The userspace side should be > >> >> > >> >> struct xen_dm_op_buf { > >> >> void *h; > >> >> size_t size; > >> >> } > >> >> > >> >> which will work sensibly for 32bit and 64bit userspace, and futureproof > >> >> (for when 128bit turns up). Its size is also a power of two which > >> >> avoids alignment issues in the array. > >> >> > >> >> The kernel already has to parse this structure anyway, and will know > the > >> >> bitness of its userspace process. We could easily (at this point) > >> >> require the kernel to turn it into the kernels bitness for forwarding on > >> >> to Xen, which covers the 32bit userspace under a 64bit kernel problem, > >> >> in a way which won't break the hypercall ABI when 128bit comes along. > >> > >> But that won't cover a 32-bit kernel. > >> > > > > Do we need to care about a 32-bit kernel for a tools-only hypercall? I > thought > > a toolstack already had to be (at least) 64-bit to match Xen. > > Why would that be? Didn't XenServer for a long time run with a > 32-bit Dom0 on top of a 64-bit Xen? See also domctl/sysctl. >
Ok, I thought the landscape had changed since then. If that's the case then a 64 bit handle seems sensible and I guess we have to deal with 128 bit when that happens. Paul > Jan _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org https://lists.xen.org/xen-devel
