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From: Aaron Lindsay <aaron@os.amperecomputing.com>
To: qemu-devel@nongnu.org, "Alex Bennée" <alex.bennee@linaro.org>
Cc: cota@braap.org, richard.henderson@linaro.org
Subject: plugins: Missing Store Exclusive Memory Accesses
Date: Thu, 16 Sep 2021 16:44:32 -0400	[thread overview]
Message-ID: <YUOssEF1lND+Rhsr@strawberry.localdomain> (raw)

Hello,

I recently noticed that the plugin interface does not appear to be
emitting callbacks to functions registered via
`qemu_plugin_register_vcpu_mem_cb` for AArch64 store exclusives. This
would include instructions like `stxp  w16, x2, x3, [x4]` (encoding:
0xc8300c82). Seeing as how I'm only running with a single CPU, I don't
see how this could be due to losing exclusivity after the preceding
`ldxp`.

In looking at QEMU's source, I *think* this is because the
`gen_store_exclusive` function in translate-a64.c is not making the same
calls to `plugin_gen_mem_callbacks` & company that are being made by
"normal" stores handled by functions like `tcg_gen_qemu_st_i64` (at
least in my case; I do see some code paths under `gen_store_exclusive`
call down into `tcg_gen_qemu_st_i64` eventually, but it appears not all
of them do?).

Does my initial guess check out? And, if so, does anyone have insight
into how to fix this issue most cleanly/generically? I suspect if/when I
debug my particular case I can discover one code path to fix, but I'm
wondering if my discovery may be part of a larger class of cases which
fell through the cracks and ought to be fixed together.

Thanks for any help,

Aaron


             reply	other threads:[~2021-09-16 20:51 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-16 20:44 Aaron Lindsay [this message]
2021-09-17 11:05 ` plugins: Missing Store Exclusive Memory Accesses Alex Bennée
2021-09-17 14:44   ` Aaron Lindsay via
2021-09-21 20:28   ` Aaron Lindsay via
2021-09-22 20:22     ` Aaron Lindsay via
2021-10-20 17:12       ` Aaron Lindsay via
2021-10-20 17:54         ` Alex Bennée
2021-10-20 20:49           ` Aaron Lindsay via
2021-10-21 12:28             ` Alex Bennée
2021-10-21 20:40               ` Aaron Lindsay via
2021-10-22  8:37                 ` Alex Bennée

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