From 67bbeb056f75adc6c964468d876531ab68366fe0 Mon Sep 17 00:00:00 2001 From: Emanuele Giuseppe Esposito Date: Thu, 9 Mar 2023 08:24:36 -0500 Subject: [PATCH 07/12] edu: add smp_mb__after_rmw() RH-Author: Emanuele Giuseppe Esposito RH-MergeRequest: 158: qatomic: add smp_mb__before/after_rmw() RH-Bugzilla: 2175660 RH-Acked-by: Paolo Bonzini RH-Acked-by: Cornelia Huck RH-Acked-by: David Hildenbrand RH-Acked-by: Eric Auger RH-Commit: [4/9] 2ad6fd6cb33fde39d2d017d94c0dde2152ad70c4 (eesposit/qemu-kvm) Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2175660 commit 2482aeea4195ad84cf3d4e5b15b28ec5b420ed5a Author: Paolo Bonzini 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 Reviewed-by: David Hildenbrand Signed-off-by: Paolo Bonzini Signed-off-by: Emanuele Giuseppe Esposito --- 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