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Re: [PATCH -tip 0/6 V4] tracing: kprobe-based event tracer
- From: Avi Kivity <avi at redhat dot com>
- To: Ingo Molnar <mingo at elte dot hu>
- Cc: Masami Hiramatsu <mhiramat at redhat dot com>, "H. Peter Anvin" <hpa at zytor dot com>, Frederic Weisbecker <fweisbec at gmail dot com>, Steven Rostedt <rostedt at goodmis dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Andrew Morton <akpm at linux-foundation dot org>, Andi Kleen <andi at firstfloor dot org>, Jim Keniston <jkenisto at us dot ibm dot com>, kvm at vger dot kernel dot org, systemtap-ml <systemtap at sources dot redhat dot com>, LKML <linux-kernel at vger dot kernel dot org>
- Date: Fri, 03 Apr 2009 15:17:06 +0300
- Subject: Re: [PATCH -tip 0/6 V4] tracing: kprobe-based event tracer
- References: <49D4F4B5.9040107@redhat.com> <20090403112639.GC31399@elte.hu> <49D5F80B.7000305@redhat.com> <20090403121202.GI31399@elte.hu>
Ingo Molnar wrote:
kvm has three requirements not needed by kprobes:
- it wants to execute instructions, not just decode them, including
generating faults where appropriate
- it is performance critical
- it needs to support 16-bit, 32-bit, and 64-bit instructions simultaneously
If an arch/x86/ decoder/emulator gives me these I'll gladly switch
to it. x86_emulate.c is high on my list of most disliked code.
Well, this has to be driven from the KVM side as the kprobes use
will only be for decoding so if it's modified from the kprobes side
the KVM-only functionality might regress.
So ... we can do the library decoder for kprobes purposes, and
someone versed in the KVM emulator can then combine the two.
Problem is, anyone versed in the kvm emulator will want to run as far
away from this work as possible.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.