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qemu-kvm/SOURCES/kvm-edu-add-smp_mb__after_r...

62 lines
2.2 KiB

From 67bbeb056f75adc6c964468d876531ab68366fe0 Mon Sep 17 00:00:00 2001
From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Date: Thu, 9 Mar 2023 08:24:36 -0500
Subject: [PATCH 07/12] edu: add smp_mb__after_rmw()
RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
RH-MergeRequest: 158: qatomic: add smp_mb__before/after_rmw()
RH-Bugzilla: 2175660
RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
RH-Acked-by: David Hildenbrand <david@redhat.com>
RH-Acked-by: Eric Auger <eric.auger@redhat.com>
RH-Commit: [4/9] 2ad6fd6cb33fde39d2d017d94c0dde2152ad70c4 (eesposit/qemu-kvm)
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2175660
commit 2482aeea4195ad84cf3d4e5b15b28ec5b420ed5a
Author: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu Mar 2 11:16:13 2023 +0100
edu: add smp_mb__after_rmw()
Ensure ordering between clearing the COMPUTING flag and checking
IRQFACT, and between setting the IRQFACT flag and checking
COMPUTING. This ensures that no wakeups are lost.
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
---
hw/misc/edu.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/hw/misc/edu.c b/hw/misc/edu.c
index e935c418d4..a1f8bc77e7 100644
--- a/hw/misc/edu.c
+++ b/hw/misc/edu.c
@@ -267,6 +267,8 @@ static void edu_mmio_write(void *opaque, hwaddr addr, uint64_t val,
case 0x20:
if (val & EDU_STATUS_IRQFACT) {
qatomic_or(&edu->status, EDU_STATUS_IRQFACT);
+ /* Order check of the COMPUTING flag after setting IRQFACT. */
+ smp_mb__after_rmw();
} else {
qatomic_and(&edu->status, ~EDU_STATUS_IRQFACT);
}
@@ -349,6 +351,9 @@ static void *edu_fact_thread(void *opaque)
qemu_mutex_unlock(&edu->thr_mutex);
qatomic_and(&edu->status, ~EDU_STATUS_COMPUTING);
+ /* Clear COMPUTING flag before checking IRQFACT. */
+ smp_mb__after_rmw();
+
if (qatomic_read(&edu->status) & EDU_STATUS_IRQFACT) {
qemu_mutex_lock_iothread();
edu_raise_irq(edu, FACT_IRQ);
--
2.39.1