On Fri, 25 Oct 2013 11:34:22 -0200 Marcelo Tosatti <mtosa...@redhat.com> wrote:
> On Fri, Oct 25, 2013 at 11:57:18AM +0200, igor Mammedov wrote: > > On Fri, 25 Oct 2013 02:58:05 -0200 > > Marcelo Tosatti <mtosa...@redhat.com> wrote: > > > > > On Fri, Oct 25, 2013 at 12:55:36AM +0100, Paolo Bonzini wrote: > > > > > + if (hpagesize == (1<<30)) { > > > > > + unsigned long holesize = 0x100000000ULL - > > > > > below_4g_mem_size; + > > > > > + memory_region_init_alias(ram_above_4g, NULL, > > > > > "ram-above-4g", ram, > > > > > + 0x100000000ULL, > > > > > + above_4g_mem_size - > > > > > holesize); > > > > > + memory_region_add_subregion(system_memory, > > > > > 0x100000000ULL, > > > > > + ram_above_4g); > > > > > + > > > > > + ram_above_4g_piecetwo = > > > > > g_malloc(sizeof(*ram_above_4g_piecetwo)); > > > > > + memory_region_init_alias(ram_above_4g_piecetwo, > > > > > NULL, > > > > > + "ram-above-4g-piecetwo", > > > > > ram, > > > > > + 0x100000000ULL - > > > > > holesize, holesize); > > > > > + memory_region_add_subregion(system_memory, > > > > > + 0x100000000ULL + > > > > > + above_4g_mem_size - > > > > > holesize, > > > > > + > > > > > ram_above_4g_piecetwo); > > > > > > > > Why break it in two? You can just allocate extra holesize > > > > bytes in the "ram" MemoryRegion, and not map the part that > > > > corresponds to [0x100000000ULL - holesize, 0x100000000ULL). > > > > > > - If the "ram" MemoryRegion is backed with 1GB hugepages, you > > > might not want to allocate extra holesize bytes (which might > > > require an entire 1GB page). > > From POV of moddeling current "ram" as dimm devices, aliasing > > wouldn't work nice. But breaking one block in two or more is fine > > since then blocks could be represented as several dimm devices. > > > > +3Gb backend ram it could be split in blocks like this: > > > > [ 3Gb (1Gb pages backed) ] > > [tail1 (below_4gb - 3Gb) (2mb pages backed) ] > > [above_4gb whole X Gb pages (1Gb pages backed)] > > [tail2 (2mb pages backed)] > > Yes, thought of that, unfortunately its cumbersome to add an interface > for the user to supply both 2MB and 1GB hugetlbfs pages. Could 2Mb tails be automated, meaning if host uses 1Gb hugepages and there is/are tail/s, QEMU should be able to figure out alignment issues and allocate with appropriate pages. Goal is separate host part allocation aspect from guest related one, aliasing 32-bit hole size at the end doesn't help it at all, it's quite opposite, it's making current code more complicated and harder to fix in the future.