From: Paolo Bonzini <pbonzini@redhat.com>
To: Peter Maydell <peter.maydell@linaro.org>,
Stefan Hajnoczi <stefanha@redhat.com>
Cc: "Marc-André Lureau" <marcandre.lureau@gmail.com>,
"Richard Henderson" <richard.henderson@linaro.org>,
"Philippe Mathieu-Daudé" <philmd@redhat.com>,
"QEMU Developers" <qemu-devel@nongnu.org>,
"Samuel Thibault" <samuel.thibault@ens-lyon.org>
Subject: Re: [PULL 0/2] Libslirp patches
Date: Mon, 5 Jul 2021 18:43:56 +0200 [thread overview]
Message-ID: <3b61a958-021d-bf2d-9fbb-09451f5fe22c@redhat.com> (raw)
In-Reply-To: <CAFEAcA9JnYri2TiB-zE1J0w26TQnUzzMe_z2XUD9YxBugJm6tg@mail.gmail.com>
On 05/07/21 18:31, Peter Maydell wrote:
> 8 here means "8 bytes", not "8 bits". And indeed on i386 you can't
> do 8-byte atomics with simple insns.
You can, there's a cmpxchg8b instruction. The problem is that somehow
configure's view of this disagrees with what happens during compilation.
If anybody can send a config.log and make V=1 log, I can look at it.
Paolo
> The compiler's answer to this
> is "emit a call to a helper in libatomic, which will emulate an
> atomic access by taking some kind of lock". We don't ever want to
> fall back to "take a lock" because sometimes our accesses to the
> atomic variables are from TCG generated code -- this is why we
> don't link against libatomic. The problem is that we have not
> correctly detected that this compiler can't do inline atomics
> for 64-bit values and avoided using them. But at least we have
> made this a compile failure rather than a silently-wrong-code bug:-)
next prev parent reply other threads:[~2021-07-05 16:44 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-29 18:55 [PULL 0/2] Libslirp patches marcandre.lureau
2021-05-29 18:55 ` [PULL 1/2] Update libslirp to v4.5.0 marcandre.lureau
2021-06-18 16:01 ` Doug Evans
2021-06-18 18:14 ` Marc-André Lureau
2021-07-27 20:05 ` Doug Evans
2021-05-29 18:55 ` [PULL 2/2] build-sys: make libslirp a meson subproject marcandre.lureau
2021-06-01 9:10 ` [PULL 0/2] Libslirp patches Peter Maydell
2021-06-01 11:01 ` Marc-André Lureau
2021-06-07 12:16 ` Peter Maydell
2021-06-08 15:55 ` Marc-André Lureau
2021-06-08 16:55 ` Peter Maydell
2021-06-08 20:35 ` Marc-André Lureau
2021-07-05 10:31 ` Philippe Mathieu-Daudé
2021-07-05 16:25 ` Stefan Hajnoczi
2021-07-05 16:31 ` Peter Maydell
2021-07-05 16:43 ` Paolo Bonzini [this message]
2021-07-05 16:47 ` Paolo Bonzini
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