[Qemu-devel] [PATCH v2 0/4] target-arm: Handle tagged addresses when loading PC

[Thomas Hanson]

If tagged addresses are enabled, then addresses being loaded into the 
PC must be cleaned up by overwriting the tag bits with either all 0's 
or all 1's as specified in the ARM ARM spec.  The decision process is 
dependent on whether the code will be running in EL0/1 or in EL2/3 and 
is controlled by a combination of Top Byte Ignored (TBI) bits in the 
TCR and the value of bit 55 in the address being loaded. 
    
TBI values are extracted from the appropriate TCR and made available 
to TCG code generation routines by inserting them into the TB flags 
field and then transferring them to DisasContext structure in 
gen_intermediate_code_a64().

New function gen_a64_set_pc_reg() encapsulates the logic required to 
determine whether clean up of the tag byte is required and then 
generating the code to correctly load the PC.
  
In addition to those instruction which can directly load a tagged 
address into the PC, there are others which increment or add a value to
the PC.  If 56 bit addressing is used, these instructions can cause an 
arithmetic roll-over into the tag bits.  The ARM ARM specification for 
handling tagged addresses requires that these cases also be addressed
by cleaning up the tag field.  This work has been deferred because 
there is currently no CPU model available for testing with 56 bit 
addresses.

v1->v2:
  - Updated patch descriptions per Peter's commments
  - Added function header and other comments as recommended
  - Change return type from long to unit32_t for arm_regime_tbi0() &
    arm_regime_tbi1()
  - Moved prototype of gen_a64_set_pc_reg() from patch 1 to patch 2
  - Moved assignment of dc->tbi0 & dc->tbi1 from patch 2 to patch 1
  - Split out documentation comments into separate patch.

  Still looking into handling of tagged addresses for exceptions and
  exception returns.  Will handle that as a separate patch set.


Thomas Hanson (4):
  target-arm: Infrastucture changes to enable handling of tagged address
    loading into PC
  target-arm: Code changes to implement overwrite of tag field on PC
    load
  target-arm: Comments to mark location of pending work for 56 bit
    addresses
  target-arm: Comments added to identify cases in a switch

 target-arm/cpu.h           |  39 ++++++++++++++++-
 target-arm/helper.c        |  46 +++++++++++++++++++++
 target-arm/translate-a64.c | 101 +++++++++++++++++++++++++++++++++++++++++----
 target-arm/translate.h     |   3 ++
 4 files changed, 179 insertions(+), 10 deletions(-)

-- 
1.9.1