[Xen-devel] [v7][RFC][PATCH 01/13] xen: RMRR fix

[Tiejun Chen <tiejun.chen@xxxxxxxxx>]

This series of patches try to reconcile those remaining problems but
just post as RFC to ask for any comments to refine everything.

The current whole scheme is as follows:

1. Reconcile guest mmio with RMRR in pci_setup
2. Reconcile guest RAM with RMRR in e820 table

Then in theory guest wouldn't access any RMRR range.

3. Just initialize all RMRR ranges as p2m_access_n in p2m table:
    gfn:mfn:p2m_access_n

Here I think we shouldn't set 1:1 to expose RMRR to guest if guest
may never have a device assignment. It can prevent from leaking RMRR.

4. We reset those mappings as 1:1:p2m_mmio_direct:p2m_ram_rw once we
have a device assignment.

5. Before we take real device assignment, any access to RMRR may issue
ept_handle_violation because of p2m_access_n. Then we just call
update_guest_eip() to return.

6. After a device assignment, guest may maliciously access RMRR ranges
although we already reserve in e820 table. In the worst-case scenario
just that device can't work well. But this behavior should be same as
native so I think we shouldn't do anything here.

7. Its not necessary to introduce any flag in ept_set_entry.

First of all, hypervisor/dom0 should be trusted. Any user should make
sure they never override any valid RMRR tables without any check. So
our original set_identity_p2m_entry() tries to set as follows:

 - gfn space unoccupied -> insert mapping; success.
 - gfn space already occupied by 1:1 RMRR mapping -> do nothing; success.
 - gfn space already occupied by other mapping -> fail.

Now in our case we add a rule:
 - if p2m_access_n is set we also set this mapping.

Another reason is that ept_set_entry is called in many scenarios to
support its own management, I think we shouldn't corrupt this mechanism
and its also difficult to cover all points.

8. We need to take a consideration grouping all devices that have same
RMRR range to make sure they're just assigned to one VM.

----------------------------------------------------------------
Jan Beulich (1):
      introduce XENMEM_reserved_device_memory_map

Tiejun Chen (12):
      tools/libxc: introduce hypercall for xc_reserved_device_memory_map
      tools/libxc: check if modules space is overlapping with reserved device 
memory
      hvmloader/util: get reserved device memory maps
      hvmloader/mmio: reconcile guest mmio with reserved device memory
      hvmloader/ram: check if guest memory is out of reserved device memory maps
      xen/x86/p2m: introduce p2m_check_reserved_device_memory
      xen/x86/p2m: set p2m_access_n for reserved device memory mapping
      xen/x86/ept: handle reserved device memory in ept_handle_violation
      xen/x86/p2m: introduce set_identity_p2m_entry
      xen:vtd: create RMRR mapping
      xen/vtd: re-enable USB device assignment
      xen/vtd: group assigned device with RMRR

 tools/firmware/hvmloader/e820.c      | 215 
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 tools/firmware/hvmloader/pci.c       |  68 
+++++++++++++++++++++++++++++++++++++++++++++++++-
 tools/firmware/hvmloader/util.c      |  66 
++++++++++++++++++++++++++++++++++++++++++++++++
 tools/firmware/hvmloader/util.h      |   6 +++++
 tools/libxc/include/xenctrl.h        |   4 +++
 tools/libxc/xc_domain.c              |  29 +++++++++++++++++++++
 tools/libxc/xc_hvm_build_x86.c       | 111 
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----------
 xen/arch/x86/hvm/vmx/vmx.c           |  14 +++++++++++
 xen/arch/x86/mm/p2m.c                |  52 
++++++++++++++++++++++++++++++++++++++
 xen/common/compat/memory.c           |  52 
++++++++++++++++++++++++++++++++++++++
 xen/common/memory.c                  |  49 ++++++++++++++++++++++++++++++++++++
 xen/drivers/passthrough/iommu.c      |  10 ++++++++
 xen/drivers/passthrough/vtd/dmar.c   |  46 +++++++++++++++++++++++++++++++++-
 xen/drivers/passthrough/vtd/dmar.h   |   3 ++-
 xen/drivers/passthrough/vtd/extern.h |   1 +
 xen/drivers/passthrough/vtd/iommu.c  |  93 
++++++++++++++++++++++++++++++++++++++++++++++++++++++--------------
 xen/drivers/passthrough/vtd/utils.c  |   7 ------
 xen/include/asm-x86/p2m.h            |  17 +++++++++++++
 xen/include/public/memory.h          |  24 +++++++++++++++++-
 xen/include/xen/iommu.h              |   4 +++
 xen/include/xlat.lst                 |   3 ++-
 21 files changed, 828 insertions(+), 46 deletions(-)

Thanks
Tiejun

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