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From 7693449b235bbab6d32a1b87fa1d0e101c786f3b Mon Sep 17 00:00:00 2001
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From: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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Date: Thu, 9 Mar 2023 08:11:14 -0500
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Subject: [PATCH 05/13] edu: add smp_mb__after_rmw()
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RH-Author: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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RH-MergeRequest: 263: qatomic: add smp_mb__before/after_rmw()
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RH-Bugzilla: 2168472
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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RH-Acked-by: Eric Auger <eric.auger@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: David Hildenbrand <david@redhat.com>
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RH-Commit: [5/10] 300901290e08b253b1278eedc39cd07c1e202b96
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2168472
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commit 2482aeea4195ad84cf3d4e5b15b28ec5b420ed5a
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Author: Paolo Bonzini <pbonzini@redhat.com>
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Date: Thu Mar 2 11:16:13 2023 +0100
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edu: add smp_mb__after_rmw()
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Ensure ordering between clearing the COMPUTING flag and checking
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IRQFACT, and between setting the IRQFACT flag and checking
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COMPUTING. This ensures that no wakeups are lost.
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Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
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Reviewed-by: David Hildenbrand <david@redhat.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
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---
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hw/misc/edu.c | 5 +++++
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1 file changed, 5 insertions(+)
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diff --git a/hw/misc/edu.c b/hw/misc/edu.c
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index e935c418d4..a1f8bc77e7 100644
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--- a/hw/misc/edu.c
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+++ b/hw/misc/edu.c
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@@ -267,6 +267,8 @@ static void edu_mmio_write(void *opaque, hwaddr addr, uint64_t val,
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case 0x20:
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if (val & EDU_STATUS_IRQFACT) {
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qatomic_or(&edu->status, EDU_STATUS_IRQFACT);
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+ /* Order check of the COMPUTING flag after setting IRQFACT. */
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+ smp_mb__after_rmw();
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} else {
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qatomic_and(&edu->status, ~EDU_STATUS_IRQFACT);
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}
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@@ -349,6 +351,9 @@ static void *edu_fact_thread(void *opaque)
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qemu_mutex_unlock(&edu->thr_mutex);
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qatomic_and(&edu->status, ~EDU_STATUS_COMPUTING);
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+ /* Clear COMPUTING flag before checking IRQFACT. */
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+ smp_mb__after_rmw();
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+
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if (qatomic_read(&edu->status) & EDU_STATUS_IRQFACT) {
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qemu_mutex_lock_iothread();
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edu_raise_irq(edu, FACT_IRQ);
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--
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2.37.3
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