Re: [PATCH v6 0/2] add new p2m type class and new p2m type

["Yu, Zhang" <yu.c.zhang@linux.intel.com>]

Hi Tim & Jan,

   Thank you very much for your review.
   And could you please also help me about how to get an ACK? I'm not 
sure what's the next action I need to take. :-)

B.R.
Yu

On 12/6/2014 11:55 AM, Yu Zhang wrote:
> 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 v5:
>   - Stricter type checks for p2m type transitions;
>   - One code style change.
>
> 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(-)
>