[Xen-devel] [PATCH v5 0/2] add new p2m type class and new p2m type

[Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>]

XenGT (Intel Graphics Virtualization technology, please refer to
https://01.org/xen/blogs/srclarkx/2013/graphics-virtualization-
xengt) driver runs inside Dom0 as a virtual graphics device model,
and needs to trap and emulate the guest's write operations to some
specific memory pages, like memory pages used by guest graphics
driver as PPGTT(per-process graphics translation table). We added
a new p2m type, p2m_mmio_write_dm, to trap and emulate the write
operations on these graphic page tables. 

Handling of this new p2m type are similar with existing p2m_ram_ro
in most condition checks, with only difference on final policy of
emulation vs. drop. For p2m_ram_ro types, write operations will not
trigger the device model, and will be discarded later in __hvm_copy();
while for the p2m_mmio_write_dm type pages, writes will go to the
device model via ioreq-server.

Previously, the conclusion in our v3 patch review is to provide a
more generalized HVMOP_map_io_range_to_ioreq_server hypercall, by
seperating rangesets inside a ioreq server to read-protected/write-
protected/both-prtected. Yet, after offline discussion with Paul,
we believe a more simplified solution may suffice. We can keep the 
existing HVMOP_map_io_range_to_ioreq_server hypercall, and let the 
user decide whether or not a p2m type change is necessary, because
in most cases the emulator will already use the p2m_mmio_dm type.

Changes from v4:
 - A new p2m type class, P2M_DISCARD_WRITE_TYPES, is added;
 - A new predicate, p2m_is_discard_write, is used in __hvm_copy()/
   __hvm_clear()/emulate_gva_to_mfn()/hvm_hap_nested_page_fault(),
   to discard the write operations;
 - The new p2m type, p2m_mmio_write_dm, is added to P2M_RO_TYPES;
 - Coding style changes;

Changes from v3:
 - Use the existing HVMOP_map_io_range_to_ioreq_server hypercall
   to add write protected range;
 - Modify the HVMOP_set_mem_type hypercall to support the new p2m
   type for this range.

Changes from v2:
 - Remove excute attribute of the new p2m type p2m_mmio_write_dm;
 - Use existing rangeset for keeping the write protection page range
   instead of introducing hash table;
 - Some code style fix.

Changes from v1:
 - Changes the new p2m type name from p2m_ram_wp to p2m_mmio_write_dm.
   This means that we treat the pages as a special mmio range instead
   of ram;
 - Move macros to c file since only this file is using them.
 - Address various comments from Jan.

Yu Zhang (2):
  Add a new p2m type class - P2M_DISCARD_WRITE_TYPES
  add a new p2m type - p2m_mmio_write_dm

 xen/arch/x86/hvm/hvm.c          | 25 ++++++++++---------------
 xen/arch/x86/mm/p2m-ept.c       |  1 +
 xen/arch/x86/mm/p2m-pt.c        |  1 +
 xen/arch/x86/mm/shadow/multi.c  |  2 +-
 xen/include/asm-x86/p2m.h       |  9 ++++++++-
 xen/include/public/hvm/hvm_op.h |  1 +
 6 files changed, 22 insertions(+), 17 deletions(-)

-- 
1.9.1


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