[Xen-devel] [PATCH 3/4] xen: arm: add barrier before sev in smp_spin_table_cpu_up

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

This ensures that the writeq to the release address has occurred.

In reality there is a dsb() in the iounmap() (in the eventual write_pte()) but
make it explicit.

The ARMv8 ARM recommends that sev() is usually accompanied by a dsb(), the
only other uses are in the v7 spinlock code which includes a dsb() already.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
v2: typos in the commit message
---
 xen/arch/arm/arm64/smpboot.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/xen/arch/arm/arm64/smpboot.c b/xen/arch/arm/arm64/smpboot.c
index 9146476..8e2ecf2 100644
--- a/xen/arch/arm/arm64/smpboot.c
+++ b/xen/arch/arm/arm64/smpboot.c
@@ -36,6 +36,7 @@ static int __init smp_spin_table_cpu_up(int cpu)
 
     iounmap(release);
 
+    dsb(); /* Ensure that the write to cpu_release_addr has occurred. */
     sev();
 
     return cpu_up_send_sgi(cpu);
-- 
1.7.10.4


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