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Re: [PATCH v1 1/7] softmmu: fix watchpoint-interrupt races

From: Richard Henderson
Subject: Re: [PATCH v1 1/7] softmmu: fix watchpoint-interrupt races
Date: Wed, 24 Nov 2021 08:38:52 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0

On 11/23/21 9:57 PM, Alex Bennée wrote:
From: Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru>

Watchpoint may be processed in two phases. First one is detecting
the instruction with target memory access. And the second one is
executing only one instruction and setting the debug interrupt flag.
Hardware interrupts can break this sequence when they happen after
the first watchpoint phase.
This patch postpones the interrupt request until watchpoint is

Signed-off-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Message-Id: <163662451431.125458.14945698834107669531.stgit@pasha-ThinkPad-X280>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
  accel/tcg/cpu-exec.c | 5 +++++
  1 file changed, 5 insertions(+)

diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 2d14d02f6c..9cb892e326 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -742,6 +742,11 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
              return true;
+        /* Process watchpoints first, or interrupts will ruin everything */
+        if (cpu->watchpoint_hit) {
+            qemu_mutex_unlock_iothread();
+            return false;
+        }

I think this is redundant with the next patch.


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