From: Stefan Hajnoczi <stefanha@redhat.com>
To: Florian Weimer <fweimer@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Fam Zheng <fam@euphon.net>,
thuth@redhat.com, Daniel Berrange <berrange@redhat.com>,
qemu-block@nongnu.org,
Richard Henderson <richard.henderson@linaro.org>,
qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>,
Warner Losh <imp@bsdimp.com>,
sguelton@redhat.com
Subject: Re: [RFC v2 1/4] tls: add macros for coroutine-safe TLS variables
Date: Thu, 2 Dec 2021 09:53:46 +0000 [thread overview]
Message-ID: <YaiXqkhGy6X7/jYw@stefanha-x1.localdomain> (raw)
In-Reply-To: <87h7bs6v4u.fsf@oldenburg.str.redhat.com>
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On Wed, Dec 01, 2021 at 07:24:33PM +0100, Florian Weimer wrote:
> * Stefan Hajnoczi:
>
> > +#elif defined(__x86_64__)
> > +#define QEMU_CO_TLS_ADDR(ret, var) \
> > + asm volatile("rdfsbase %0\n\t" \
> > + "lea "#var"@tpoff(%0), %0" : "=r"(ret))
> > +#endif
>
> RDFSBASE needs quite recent kernels. I think you should use
>
> movq %%fs:0, %0
>
> instead, which is equivalent for the x86-64 psABI.
Nice trick! I remember reading that the address of the thread data is
stored in the first element of the thread data itself, so this makes
sense :).
Stefan
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next prev parent reply other threads:[~2021-12-02 13:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-12-01 17:01 [RFC v2 0/4] tls: add macros for coroutine-safe TLS variables Stefan Hajnoczi
2021-12-01 17:01 ` [RFC v2 1/4] " Stefan Hajnoczi
2021-12-01 18:24 ` Florian Weimer
2021-12-02 9:53 ` Stefan Hajnoczi [this message]
2021-12-02 14:44 ` Peter Maydell
2021-12-02 14:50 ` Peter Maydell
2021-12-02 14:57 ` Florian Weimer
2021-12-03 6:24 ` Serge Guelton
2021-12-01 17:01 ` [RFC v2 2/4] util/async: replace __thread with QEMU TLS macros Stefan Hajnoczi
2021-12-01 17:01 ` [RFC v2 3/4] rcu: use coroutine " Stefan Hajnoczi
2021-12-01 17:01 ` [RFC v2 4/4] cpus: use coroutine TLS macros for iothread_locked Stefan Hajnoczi
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