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Re: [Qemu-devel] [PATCH v2 2/2] trace: separate MMIO tracepoints from TB

From: Hollis Blanchard
Subject: Re: [Qemu-devel] [PATCH v2 2/2] trace: separate MMIO tracepoints from TB-access tracepoints
Date: Mon, 7 Mar 2016 13:32:48 -0800

On Wed, 2016-03-02 at 12:12 -0800, Hollis Blanchard wrote:
Memory accesses to code which has previously been translated into a TB show up
in the MMIO path, so that they may invalidate the TB. It's extremely confusing
to mix those in with device MMIOs, so split them into their own tracepoint.

Signed-off-by: Hollis Blanchard <address@hidden>
Reviewed-by: Stefan Hajnoczi <address@hidden>
It took many hours to figure out why some RAM accesses were coming through the
MMIO path instead of being handled inline in the TBs.

On IRC, Paolo expressed some concern about performance, but ultimately agreed
that adding one conditional to an already heavy codepath wouldn't have much

v2: rename trace_memory_region_ops_tb_read/write to

Stefan, any further comment here? You sent a Reviewed-by on the original, but unlike the "include CPU index" patch, you didn't mention adding this one to https://github.com/stefanha/qemu/commits/tracing.

Hollis Blanchard <address@hidden>
Mentor Graphics Emulation Division

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