[Qemu-devel] [mttcg RFC v4 2/6] cputlb: wrap tlb_flush with the a new function

[Alvise Rigo <a.rigo@virtualopensystems.com>]

Introduce the new tlb_query_flush_cpu function to query a TLB flush
to a given vCPU.
The function takes care to check and set a new flag (pending_tlb_flush)
to avoid unnecessary flushes.

Signed-off-by: Alvise Rigo <a.rigo@virtualopensystems.com>
---
 cputlb.c                | 21 ++++++++++++++++-----
 include/exec/exec-all.h |  1 +
 include/qom/cpu.h       |  4 ++++
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/cputlb.c b/cputlb.c
index 538c92d..7cbaaca 100644
--- a/cputlb.c
+++ b/cputlb.c
@@ -79,13 +79,27 @@ static void tlb_flush_async_work(void *opaque)
     struct TLBFlushParams *params = opaque;
 
     tlb_flush(params->cpu, params->flush_global);
+    atomic_set(&params->cpu->pending_tlb_flush, 0);
+
     g_free(params);
 }
 
+void tlb_query_flush_cpu(CPUState *cpu, int flush_global) {
+    struct TLBFlushParams *params;
+
+    if (!atomic_read(&cpu->pending_tlb_flush)) {
+        params = g_malloc(sizeof(struct TLBFlushParams));
+        params->cpu = cpu;
+        params->flush_global = flush_global;
+
+        atomic_set(&cpu->pending_tlb_flush, 1);
+        async_run_on_cpu(cpu, tlb_flush_async_work, params);
+    }
+}
+
 void tlb_flush_all(int flush_global)
 {
     CPUState *cpu;
-    struct TLBFlushParams *params;
 
 #if 0 /* MTTCG */
     CPU_FOREACH(cpu) {
@@ -99,10 +113,7 @@ void tlb_flush_all(int flush_global)
              */
             tlb_flush(cpu, flush_global);
         } else {
-            params = g_malloc(sizeof(struct TLBFlushParams));
-            params->cpu = cpu;
-            params->flush_global = flush_global;
-            async_run_on_cpu(cpu, tlb_flush_async_work, params);
+            tlb_query_flush_cpu(cpu, flush_global);
         }
     }
 #endif /* MTTCG */
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 246df68..3c36724 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -99,6 +99,7 @@ void tcg_cpu_address_space_init(CPUState *cpu, AddressSpace *as);
 /* cputlb.c */
 void tlb_flush_page_all(target_ulong addr);
 void tlb_flush_page(CPUState *cpu, target_ulong addr);
+void tlb_query_flush_cpu(CPUState *cpu, int flush_global);
 void tlb_flush_all(int flush_global);
 void tlb_flush(CPUState *cpu, int flush_global);
 void tlb_set_page(CPUState *cpu, target_ulong vaddr,
diff --git a/include/qom/cpu.h b/include/qom/cpu.h
index 23418c0..62abf6e 100644
--- a/include/qom/cpu.h
+++ b/include/qom/cpu.h
@@ -299,6 +299,10 @@ struct CPUState {
 
     void *opaque;
 
+    /* True if the CPU has a pending request for a TLB flush. While this value
+     * is true, any flush request will be ignored. */
+    int pending_tlb_flush;
+
     /* In order to avoid passing too many arguments to the MMIO helpers,
      * we store some rarely used information in the CPU context.
      */
-- 
2.5.0