• Jeremy Fitzhardinge's avatar
    xen: convert p2m to a 3 level tree · 58e05027
    Jeremy Fitzhardinge authored
    Make the p2m structure a 3 level tree which covers the full possible
    physical space.
    
    The p2m structure contains mappings from the domain's pfns to system-wide
    mfns.  The structure has 3 levels and two roots.  The first root is for
    the domain's own use, and is linked with virtual addresses.  The second
    is all mfn references, and is used by Xen on save/restore to allow it to
    update the p2m mapping for the domain.
    
    At boot, the domain builder provides a simple flat p2m array for all the
    initially present pages.  We construct the two levels above that using
    the early_brk allocator.  After early boot time, set_phys_to_machine()
    will allocate any missing levels using the normal kernel allocator
    (at GFP_KERNEL, so it must be called in a normal blocking context).
    
    Because the early_brk() API requires us to pre-reserve the maximum amount
    of memory we could allocate, there is still a CONFIG_XEN_MAX_DOMAIN_MEMORY
    config option, but its only negative side-effect is to increase the
    kernel's apparent bss size.  However, since all unused brk memory is
    returned to the heap, there's no real downside to making it large.
    Signed-off-by: default avatarJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
    58e05027
mmu.c 61.4 KB