Re: [PATCH] accel/tcg: Use TLB_FORCE_SLOW not TLB_MMIO for user-only plugins

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> In 6d03226b422 we set TLB_MMIO to a non-zero value for user-only
> so that we could return a non-zero value from probe_* functions
> so that we could force callers like Arm SVE vector moves to use
> the slow path rather than direct access.  All for the sake of
> exposing these accesses to plugins.
>
> Back then, TLB_FORCE_SLOW did not exist, so TLB_MMIO seemed like
> a reasonable solution.  However, user-only doesn't really have
> MMIO and this has knock-on effects, like forcing Arm SVE first-fault
> vector loads to stop.  Better to use TLB_FORCE_SLOW as a more exact
> exact trigger for plugins.
>
> Cc: qemu-stable@nongnu.org
> Fixes: 6d03226b422 ("plugins: force slow path when plugins instrument memory ops")
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Acked-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro