[Xen-devel] [RFC 12/16] gic-v2: Write HCR only on change

[Andrii Anisov <andrii.anisov@xxxxxxxxx>]

From: Andrii Anisov <andrii_anisov@xxxxxxxx>

This saves one write to peripheral HCR register per hypervisor entry for
most cases.

Signed-off-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
---
 xen/arch/arm/gic-v2.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/gic-v2.c b/xen/arch/arm/gic-v2.c
index 1a744c5..25147bd 100644
--- a/xen/arch/arm/gic-v2.c
+++ b/xen/arch/arm/gic-v2.c
@@ -579,14 +579,17 @@ static void gicv2_write_lr(int lr, const struct gic_lr 
*lr_reg)
 
 static void gicv2_hcr_status(uint32_t flag, bool status)
 {
-    uint32_t hcr = readl_gich(GICH_HCR);
+    uint32_t hcr, ohcr;
+
+    ohcr = hcr = readl_gich(GICH_HCR);
 
     if ( status )
         hcr |= flag;
     else
         hcr &= (~flag);
 
-    writel_gich(hcr, GICH_HCR);
+    if ( hcr != ohcr )
+        writel_gich(hcr, GICH_HCR);
 }
 
 static unsigned int gicv2_read_vmcr_priority(void)
-- 
2.7.4


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