Re: [PATCH 0/5] tcg: Issue memory barriers for guest memory model

[Richard Henderson <richard.henderson@linaro.org>]

Ping.  A local rebase seems to apply clean.

r~

On 3/16/21 3:07 PM, Richard Henderson wrote:
> This is intending to fix the current aarch64 host failure
> for s390x guest cdrom-test.  This is caused by the io thread
> issuing memory barriers that are supposed to be matched by
> the vcpu, but are elided by tcg in rr mode as "unnecessary".
> 
> I know Peter would like a smaller patch to sync the io thread
> with the vcpu thread.  I've made a couple of attempts at this,
> but havn't managed to get something reliable (although now
> irritatingly infrequent -- about 1 in 500).
> 
> I have further patches to further optimize barriers, and to
> generate load-acquire/store-release instructions in tcg.
> But it's late in the release cycle, etc etc.
> 
> I've done nothing to measure the performance impact of this.
> I quit the cdtom-test cycle after 4000 passes.
> 
> 
> r~
> 
> 
> Richard Henderson (5):
>    tcg: Decode the operand to INDEX_op_mb in dumps
>    tcg: Do not elide memory barriers for CF_PARALLEL
>    tcg: Elide memory barriers implied by the host memory model
>    tcg: Create tcg_req_mo
>    tcg: Add host memory barriers to cpu_ldst.h interfaces
> 
>   include/exec/cpu_ldst.h |  7 ++++
>   include/tcg/tcg.h       | 20 +++++++++++
>   accel/tcg/cputlb.c      |  2 ++
>   accel/tcg/tcg-all.c     |  6 +---
>   accel/tcg/user-exec.c   | 17 +++++++++
>   tcg/tcg-op.c            | 19 +++++-----
>   tcg/tcg.c               | 79 +++++++++++++++++++++++++++++++++++++++++
>   7 files changed, 137 insertions(+), 13 deletions(-)
>