Finish initializing the memory subsystem by mapping the direct map and
frame table.

In the case of RISC-V 64, which has a large virtual address space
(the minimum supported MMU mode is Sv39, providing GBs of VA space),
so frame table is mapped starting from physical address
0 to ram_end.
This simplifies the calculations and thereby improves performance for
page_to_mfn(), mfn_to_page() as there is no frametable_base_pdx or
frametable_base_mfn ( if CONFIG_PDX_COMPRESSION=n).

The directmap_virt_start is introduced and shifted lower in the VA space to
(DIRECTMAP_VIRT_START - masked_low_bits_of_ram_start_address) to avoid
wasting a large portion of the directmap space, this also allows for simple
VA <-> PA translations. Also aligns DIRECTMAP_VIRT_START to a GB boundary
(for Sv39; for other MMU mode boundaries will be bigger ) by masking the
higher bits of the RAM start address to enable the use of superpages in
map_pages_to_xen().

In addition, initialize the VMAP_DEFAULT region, finalize the boot allocator,
and update the system state from early_boot to boot.

Introduce share_xen_page_with_guest() to deal with linkage error which occurs
because of DCE:
  riscv64-linux-gnu-ld: prelink.o: in function `tasklet_kill':
  /build/xen/common/tasklet.c:176: undefined reference to
     `share_xen_page_with_guest'
  riscv64-linux-gnu-ld: ./.xen-syms.0: hidden symbol `share_xen_page_with_guest'
    isn't defined riscv64-linux-gnu-ld: final link failed: bad value

The function maddr_to_virt() is introduced as part of this patch series.

virt_to_maddr() is updated as it is started to use direct_virt_start which is
introduced in this patch series.

---
Changes in V3:
 - Update the cover letter message as DIRECTMAP connected things were changed.
 - Update setup_mm(), setup_{directmap,frametable}_mappings.
 - Introduce ROUNDDOWN in <xen/macros.h>
 - All other details please look at the specific patch.
---
Changes in V2:
 - update the cover letter message.
 - merge first 3 patches to "introduce setup_mm()" patch as after setup_mm()
   rework all the things in first two patches of v1 started to use changes
   introduced in "introduce setup_mm()" patch.
 - add Acked-by for some patch series.
 - All other details please look at the specific patch.
---

Oleksii Kurochko (3):
  xen/riscv: introduce setup_mm()
  xen/riscv: initialize the VMAP_DEFAULT virtual range
  xen/riscv: finalize boot allocator and transition to boot state

 xen/arch/riscv/include/asm/mm.h    |  13 ++-
 xen/arch/riscv/include/asm/setup.h |   2 +
 xen/arch/riscv/mm.c                | 152 +++++++++++++++++++++++++++--
 xen/arch/riscv/pt.c                |   6 ++
 xen/arch/riscv/setup.c             |  14 +++
 xen/include/xen/macros.h           |   1 +
 6 files changed, 178 insertions(+), 10 deletions(-)

-- 
2.47.0