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Re: [Qemu-devel] [RFC 00/30] cmpxchg-based emulation of atomics
From: |
Lluís Vilanova |
Subject: |
Re: [Qemu-devel] [RFC 00/30] cmpxchg-based emulation of atomics |
Date: |
Tue, 28 Jun 2016 10:45:28 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) |
Emilio G Cota writes:
[...]
> - What to do when atomic ops are used on something other than RAM?
> Should we have a "slow path" that is not atomic for these cases, or
> it's OK to assume code is bogus? For now, I just wrote XXX.
[...]
You mean, for example, on I/O space? In these cases, it depends on the specific
device you're accessing and the interconnect used to access it.
TL;DR: In some cases, it makes sense to support atomics outside RAM.
For example, PCIe has support for expressing atomic operations in its messages
(I'm sure other interconnects do too). But in the end it depends on whether the
device supports them (I'm not sure if the device can reject atomics and produce
an error to whomever tried to do the atomic access, or if they are simply
ignored).
Cheers,
Lluis
- [Qemu-devel] [RFC 29/30] linux-user: remove handling of aarch64's EXCP_STREX, (continued)
- [Qemu-devel] [RFC 29/30] linux-user: remove handling of aarch64's EXCP_STREX, Emilio G. Cota, 2016/06/27
- [Qemu-devel] [RFC 20/30] target-i386: remove helper_lock(), Emilio G. Cota, 2016/06/27
- [Qemu-devel] [RFC 26/30] target-arm: add cmpxchg helpers for aarch64, Emilio G. Cota, 2016/06/27
- [Qemu-devel] [RFC 17/30] target-i386: emulate LOCK'ed BTX ops using atomic helpers, Emilio G. Cota, 2016/06/27
- [Qemu-devel] [RFC 24/30] target-arm: emulate SWP with atomic_xchg helper, Emilio G. Cota, 2016/06/27
- [Qemu-devel] [RFC 30/30] target-arm: remove EXCP_STREX + cpu_exclusive_{test, info}, Emilio G. Cota, 2016/06/27
- [Qemu-devel] [RFC 18/30] target-i386: emulate XCHG using atomic helper, Emilio G. Cota, 2016/06/27
- [Qemu-devel] [RFC 28/30] linux-user: remove handling of ARM's EXCP_STREX, Emilio G. Cota, 2016/06/27
- [Qemu-devel] [RFC 21/30] target-arm: add cmpxchg helpers, Emilio G. Cota, 2016/06/27
- [Qemu-devel] [RFC 19/30] tests: add atomic_add-bench, Emilio G. Cota, 2016/06/27
- Re: [Qemu-devel] [RFC 00/30] cmpxchg-based emulation of atomics,
Lluís Vilanova <=