[Xen-devel] [RFC v2 03/16] gic:vgic:gic-vgic: introduce non-atomic bitops

[Andrii Anisov <andrii.anisov@xxxxxxxxx>]

From: Andrii Anisov <andrii_anisov@xxxxxxxx>

All bit operations for gic, vgic and gic-vgic are performed under
spinlocks, so there is no need for atomic bit ops here, they only
introduce excessive call to functions used more expensive exclusive
ARM instructions.

Signed-off-by: Andrii Anisov <andrii_anisov@xxxxxxxx>
---

This patch was not changed. Its only here to list what is really
evaluated for IRQ latency impact. So ugly non-atomic bitops are still
here.
Moreover, taking in cosideration this [1], a closer look is needed
into bitops in XEN on ARM.

[1] https://lists.xenproject.org/archives/html/xen-devel/2018-11/msg03425.html

---
 xen/arch/arm/gic-vgic.c | 16 ++++++++++++++++
 xen/arch/arm/gic.c      | 16 ++++++++++++++++
 xen/arch/arm/vgic.c     | 16 ++++++++++++++++
 3 files changed, 48 insertions(+)

diff --git a/xen/arch/arm/gic-vgic.c b/xen/arch/arm/gic-vgic.c
index 471e2d0..0f8f8d5 100644
--- a/xen/arch/arm/gic-vgic.c
+++ b/xen/arch/arm/gic-vgic.c
@@ -25,6 +25,22 @@
 #include <asm/gic.h>
 #include <asm/vgic.h>
 
+#undef set_bit
+#define set_bit(nr, addr) (*(addr) |= (1<<nr))
+
+#undef clear_bit
+#define clear_bit(nr, addr) (*(addr) &= ~(1<<nr))
+
+#undef test_bit
+#define test_bit(nr,addr) (*(addr) & (1<<nr))
+
+#undef test_and_clear_bit
+#define test_and_clear_bit(nr,addr) ({                    \
+    bool _x; \
+    _x = (*(addr) & (1<<nr));                        \
+    (*(addr) &= ~(1<<nr));                                \
+    (_x);})
+
 #define lr_all_full() (this_cpu(lr_mask) == ((1 << gic_get_nr_lrs()) - 1))
 
 #undef GIC_DEBUG
diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
index 77fc06f..f576b66 100644
--- a/xen/arch/arm/gic.c
+++ b/xen/arch/arm/gic.c
@@ -40,6 +40,22 @@
 
 DEFINE_PER_CPU(uint64_t, lr_mask);
 
+#undef set_bit
+#define set_bit(nr, addr) (*(addr) |= (1<<nr))
+
+#undef clear_bit
+#define clear_bit(nr, addr) (*(addr) &= ~(1<<nr))
+
+#undef test_bit
+#define test_bit(nr,addr) (*(addr) & (1<<nr))
+
+#undef test_and_clear_bit
+#define test_and_clear_bit(nr,addr) ({                    \
+    bool _x; \
+    _x = (*(addr) & (1<<nr));                        \
+    (*(addr) &= ~(1<<nr));                                \
+    (_x);})
+
 #undef GIC_DEBUG
 
 const struct gic_hw_operations *gic_hw_ops;
diff --git a/xen/arch/arm/vgic.c b/xen/arch/arm/vgic.c
index 458b2a8..057a721 100644
--- a/xen/arch/arm/vgic.c
+++ b/xen/arch/arm/vgic.c
@@ -33,6 +33,22 @@
 #include <asm/gic.h>
 #include <asm/vgic.h>
 
+#undef set_bit
+#define set_bit(nr, addr) (*(addr) |= (1<<nr))
+
+#undef clear_bit
+#define clear_bit(nr, addr) (*(addr) &= ~(1<<nr))
+
+#undef test_bit
+#define test_bit(nr,addr) (*(addr) & (1<<nr))
+
+#undef test_and_clear_bit
+#define test_and_clear_bit(nr,addr) ({                    \
+    bool _x = (*(addr) & (1<<nr));                        \
+    (*(addr) &= ~(1<<nr));                                \
+    return (_x);                                                 \
+})
+
 static inline struct vgic_irq_rank *vgic_get_rank(struct vcpu *v, int rank)
 {
     if ( rank == 0 )
-- 
2.7.4


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