From: "H. Peter Anvin" <h.peter.anvin@intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andy Lutomirski <luto@amacapital.net>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Gleb Natapov <gleb@kernel.org>
Subject: Re: [RFC/HACK] x86: Fast return to kernel
Date: Sun, 04 May 2014 16:49:12 -0700 [thread overview]
Message-ID: <5366D1F8.5040006@intel.com> (raw)
In-Reply-To: <5366D163.9000503@redhat.com>
On 05/04/2014 04:46 PM, Paolo Bonzini wrote:
>
> Your suggested trick of splitting the return paths for IF=0/IF=1 can be
> also done like this:
>
> movq EFLAGS-ARGOFFSET(%rsp), %rdi
> btrq $9, %rdi # Clear IF, save old value in CF
> movq %rdi, (%rsi)
> ...
> popfq
> jnc 1f # If IF was 0, just return
> sti # Using STI gets us an interrupt shadow
> 1f:
> retq
>
That doesn't work, because CF gets restored by the popfq as well.
Unfortunately.
-hpa
next prev parent reply other threads:[~2014-05-04 23:49 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-02 19:04 [RFC/HACK] x86: Fast return to kernel Andy Lutomirski
2014-05-02 19:31 ` Linus Torvalds
2014-05-02 19:50 ` Andy Lutomirski
2014-05-04 18:40 ` Ingo Molnar
2014-05-04 19:59 ` H. Peter Anvin
2014-05-04 21:31 ` Linus Torvalds
2014-05-04 22:01 ` H. Peter Anvin
2014-05-02 19:51 ` Linus Torvalds
2014-05-02 20:07 ` H. Peter Anvin
2014-05-02 20:30 ` Thomas Gleixner
2014-05-02 21:01 ` Linus Torvalds
2014-05-02 21:04 ` Andy Lutomirski
2014-05-02 21:07 ` Linus Torvalds
2014-05-02 21:37 ` H. Peter Anvin
2014-05-02 21:42 ` Andy Lutomirski
2014-05-02 21:44 ` H. Peter Anvin
2014-05-02 21:28 ` Thomas Gleixner
2014-05-04 23:46 ` Paolo Bonzini
2014-05-04 23:49 ` H. Peter Anvin [this message]
2014-05-02 20:19 ` Steven Rostedt
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