From: Richard Henderson <richard.henderson@linaro.org>
Date: Thu, 23 Feb 2023 09:05:01 +0000 (-1000)
Subject: accel/tcg: Honor TLB_DISCARD_WRITE in atomic_mmu_lookup
X-Git-Tag: qemu-xen-4.18.0-rc5~288^2~78
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=0953674ed0acacfa9b2409678f8ce8333398ee1c;p=qemu-xen.git

accel/tcg: Honor TLB_DISCARD_WRITE in atomic_mmu_lookup

Using an atomic write or read-write insn on ROM is basically
a happens-never case.  Handle it via stop-the-world, which
will generate non-atomic serial code, where we can correctly
ignore the write while producing the correct read result.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---

diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index deafcc7f15..b49fb0d754 100644
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -1831,7 +1831,7 @@ static void *atomic_mmu_lookup(CPUArchState *env, target_ulong addr,
     }
 
     /* Notice an IO access or a needs-MMU-lookup access */
-    if (unlikely(tlb_addr & TLB_MMIO)) {
+    if (unlikely(tlb_addr & (TLB_MMIO | TLB_DISCARD_WRITE))) {
         /* There's really nothing that can be done to
            support this apart from stop-the-world.  */
         goto stop_the_world;