[PATCH] powerpc/sstep: Fix VSX instruction emulation

[Ravi Bangoria]

On 2/25/21 8:49 AM, Jordan Niethe wrote:
> Commit af99da74333b ("powerpc/sstep: Support VSX vector paired storage
> access instructions") added loading and storing 32 word long data into
> adjacent VSRs. However the calculation used to determine if two VSRs
> needed to be loaded/stored inadvertently prevented the load/storing
> taking place for instructions with a data length less than 16 words.
> 
> This causes the emulation to not function correctly, which can be seen
> by the alignment_handler selftest:
> 
> $ ./alignment_handler
> [snip]
> test: test_alignment_handler_vsx_207
> tags: git_version:powerpc-5.12-1-0-g82d2c16b350f
> VSX: 2.07B
>          Doing lxsspx:   PASSED
>          Doing lxsiwax:  FAILED: Wrong Data
>          Doing lxsiwzx:  PASSED
>          Doing stxsspx:  PASSED
>          Doing stxsiwx:  PASSED
> failure: test_alignment_handler_vsx_207
> test: test_alignment_handler_vsx_300
> tags: git_version:powerpc-5.12-1-0-g82d2c16b350f
> VSX: 3.00B
>          Doing lxsd:     PASSED
>          Doing lxsibzx:  PASSED
>          Doing lxsihzx:  PASSED
>          Doing lxssp:    FAILED: Wrong Data
>          Doing lxv:      PASSED
>          Doing lxvb16x:  PASSED
>          Doing lxvh8x:   PASSED
>          Doing lxvx:     PASSED
>          Doing lxvwsx:   FAILED: Wrong Data
>          Doing lxvl:     PASSED
>          Doing lxvll:    PASSED
>          Doing stxsd:    PASSED
>          Doing stxsibx:  PASSED
>          Doing stxsihx:  PASSED
>          Doing stxssp:   PASSED
>          Doing stxv:     PASSED
>          Doing stxvb16x: PASSED
>          Doing stxvh8x:  PASSED
>          Doing stxvx:    PASSED
>          Doing stxvl:    PASSED
>          Doing stxvll:   PASSED
> failure: test_alignment_handler_vsx_300
> [snip]
> 
> Fix this by making sure all VSX instruction emulation correctly
> load/store from the VSRs.
> 
> Fixes: af99da74333b ("powerpc/sstep: Support VSX vector paired storage access instructions")
> Signed-off-by: Jordan Niethe <jniethe5 at gmail.com>

Yikes!

Reviewed-by: Ravi Bangoria <ravi.bangoria at linux.ibm.com>