On Tue, Sep 01, 2015 at 05:01:07PM -0700, Nakajima, Jun wrote: > On Tue, Sep 1, 2015 at 9:28 AM, Jan Kiszka <jan.kis...@siemens.com> wrote: > > On 2015-09-01 18:02, Michael S. Tsirkin wrote: > ... > >> You don't need to be able to map all guest memory if you know > >> guest won't try to allow device access to all of it. > >> It's a question of how good is the bus address allocator. > > > > But those BARs need to allocate a guest-physical address range as large > > as the other guest's RAM is, possibly even larger if that RAM is not > > contiguous, and you can't put other resources into potential holes > > because VM2 does not know where those holes will be. > > > > I think you can allocate such guest-physical address ranges > efficiently if each BAR sets the base of each memory region reported > by VHOST_SET_MEM_TABLE, for example. The issue is that we would need > to 8 (VHOST_MEMORY_MAX_NREGIONS) of them vs. 6 (defined by PCI-SIG).
Besides, 8 is not even a limit: we merged a patch that allows makeing it larger. > -- > Jun > Intel Open Source Technology Center
