[Qemu-devel] [PATCH] exec.c: Clarify comment about tlb_flush() flush_global parameter

[Peter Maydell]

Clarify the comment about tlb_flush()'s flush_global parameter,
so it is clearer what it does and why it is OK that the implementation
currently ignores it.

Signed-off-by: Peter Maydell <address@hidden>
---
Minor clarification following a conversation on IRC...

 exec.c |   14 ++++++++++++--
 1 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/exec.c b/exec.c
index 7f9f730..f667cf0 100644
--- a/exec.c
+++ b/exec.c
@@ -1876,8 +1876,18 @@ static CPUTLBEntry s_cputlb_empty_entry = {
     .addend     = -1,
 };
 
-/* NOTE: if flush_global is true, also flush global entries (not
-   implemented yet) */
+/* NOTE:
+ * If flush_global is true (the usual case), flush all tlb entries.
+ * If flush_global is false, flush (at least) all tlb entries not
+ * marked global.
+ *
+ * Since QEMU doesn't currently implement a global/not-global flag
+ * for tlb entries, at the moment tlb_flush() will also flush all
+ * tlb entries in the flush_global == false case. This is OK because
+ * CPU architectures generally permit an implementation to drop
+ * entries from the TLB at any time, so flushing more entries than
+ * required is only an efficiency issue, not a correctness issue.
+ */
 void tlb_flush(CPUState *env, int flush_global)
 {
     int i;
-- 
1.7.1