[v5,0/3] drop writes to read-only ram device & vfio regions

Message

Yan Zhao April 30, 2020, 5:15 a.m. UTC

guest writes to read-only memory regions need to be dropped.

patch 1 modifies handler of ram device memory regions to drop guest writes
to read-only ram device memory regions

patch 2 modifies handler of non-mmap'd read-only vfio regions to drop guest
writes to those regions 

patch 3 set read-only flag to mmap'd read-only vfio regions, so that guest
writes to those regions would be trapped.
without patch 1, host qemu would then crash on guest write to those
read-only regions.
with patch 1, host qemu would drop the writes.

Changelog:
v5:
-changed write handler of ram device memory region from .write to
.write_with_attrs in patch 1 (Paolo)
(for vfio region in patch 2, I still keep the operations as .read & .write.
the reasons are:
1. vfio_region_ops are for mmio/pio regions. the top level read/write
dispatcher in kvm just ignores their return values. (the return value of
address_space_rw() is just ignored)
2. there are a lot of callers to vfio_region_read() and
vfio_region_write(), who actually do not care about the return values
)
-minor changes on text format in error logs.

v4:
-instead of modifying tracing log, added qemu_log_mask(LOG_GUEST_ERROR...)
to log guest writes to read-only regions (Philippe)

for
v3:
-refreshed and Cc Stefan for reviewing of tracing part

v2:
-split one big patches into smaller ones (Philippe)
-modify existing trace to record guest writes to read-only memory (Alex)
-modify vfio_region_write() to drop guest writes to non-mmap'd read-only
 region (Alex)



Yan Zhao (3):
  memory: drop guest writes to read-only ram device regions
  hw/vfio: drop guest writes to ro regions
  hw/vfio: let read-only flag take effect for mmap'd regions

 hw/vfio/common.c | 17 +++++++++++++++--
 memory.c         | 15 ++++++++++++---
 2 files changed, 27 insertions(+), 5 deletions(-)