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Re: [Xen-devel] [PATCH 4/4] xen/arm: gic: Relax barrier when sending an SGI

On 10/24/18 2:32 PM, Andrii Anisov wrote:
Hello Julien,

Hi Andrii,

On 23.10.18 21:17, Julien Grall wrote:
diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 0108e9603c..077b941b79 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -300,12 +300,6 @@ void send_SGI_mask(const cpumask_t *cpumask, enum gic_sgi 
       ASSERT(sgi < 16); /* There are only 16 SGIs */
- /*
-    * Ensure that stores to Normal memory are visible to the other CPUs
-    * before issuing the IPI.
-    * Matches the read barrier in do_sgi.
-    */
-    dsb(sy);
Here you remove the comment you've just added within this patch series,
and the same below.
Wouldn't it better to reorder patches, first relax the barrier, then
ensure ordering between read of INTACK and shared data?

patch #1 and #2 should be backported. This patch is technically not a bug fix but a relaxation. So I am not comfortable to suggest backporting it up to Xen 4.9. Hence the ordering of the series.


Julien Grall

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