cputlb: introduce tlb_flush_* async work.

Some architectures allow to flush the tlb of other VCPUs. This is not a problem
when we have only one thread for all VCPUs but it definitely needs to be an
asynchronous work when we are in true multithreaded work.

We take the tb_lock() when doing this to avoid racing with other threads
which may be invalidating TB's at the same time. The alternative would
be to use proper atomic primitives to clear the tlb entries en-mass.

This patch doesn't do anything to protect other cputlb function being
called in MTTCG mode making cross vCPU changes.

Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
[AJB: remove need for g_malloc on defer, make check fixes, tb_lock]
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 10db89b16a..e80bf7a64a 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -402,6 +402,12 @@ struct CPUState {
 
     bool hax_vcpu_dirty;
     struct hax_vcpu_state *hax_vcpu;
+
+    /* The pending_tlb_flush flag is set and cleared atomically to
+     * avoid potential races. The aim of the flag is to avoid
+     * unnecessary flushes.
+     */
+    bool pending_tlb_flush;
 };
 
 QTAILQ_HEAD(CPUTailQ, CPUState);