accel/tcg: Test CPUJumpCache in tb_jmp_cache_clear_page

After commit 4e4fa6c12d ("accel/tcg: Complete cpu initialization
before registration"), it looks the CPUJumpCache pointer can be NULL.
This causes a SIGSEV when running debug-wp-migration kvm unit test.

At the first place it should be clarified why this TCG code is called
with KVM acceleration. This may hide another bug.

Fixes: 4e4fa6c12d ("accel/tcg: Complete cpu initialization before registration")
Signed-off-by: Eric Auger <eric.auger@redhat.com>
Message-Id: <20230203171510.2867451-1-eric.auger@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index 4e040a1cb9cc9eabae9e4ed8e682cd4d1001159f..04e270742ebc2c606b205d004183c54a8d9d430e 100644 (file)
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -100,9 +100,14 @@ static void tlb_window_reset(CPUTLBDesc *desc, int64_t ns,
 
 static void tb_jmp_cache_clear_page(CPUState *cpu, target_ulong page_addr)
 {
-    int i, i0 = tb_jmp_cache_hash_page(page_addr);
     CPUJumpCache *jc = cpu->tb_jmp_cache;
+    int i, i0;
 
+    if (unlikely(!jc)) {
+        return;
+    }
+
+    i0 = tb_jmp_cache_hash_page(page_addr);
     for (i = 0; i < TB_JMP_PAGE_SIZE; i++) {
         qatomic_set(&jc->array[i0 + i].tb, NULL);
     }