[PATCH v4 2/4] xen/arm: optimize the size of struct vcpu

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

When CONFIG_NEW_VGIC=y and CONFIG_ARM_64=y, the size of struct vcpu
exceeds one page, which requires allocating two pages and led to the
introduction of MAX_PAGES_PER_VCPU.

To remove the need for MAX_PAGES_PER_VCPU in a follow-up patch, the vgic
member of NEW_VGIC's struct vgic_vcpu member private_irq is changed to a
pointer to struct vgic_irq.
As a result, the size of struct vcpu for Arm64 is reduced to 2176 bytes,
compared to 3840 bytes (without these changes and with CONFIG_ARM_64=y)
and 4736 bytes (without these changes and with both CONFIG_ARM_64=y and
CONFIG_NEW_VGIC=y).

Since the private_irqs member is now a pointer, vcpu_vgic_init() and
vcpu_vgic_free() are updated to allocate and free private_irqs instance.

Suggested-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
Change in v4:
 - Add Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>.
---
Changes in v3:
 - Make private_irqs member as pointer to vgic_irq in struct vgic_cpu
   of new_vgic instead of vgic member of arch_vcpu.
---
Changes in v2:
 - New patch.
---
 xen/arch/arm/include/asm/new_vgic.h | 2 +-
 xen/arch/arm/vgic/vgic-init.c       | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/include/asm/new_vgic.h 
b/xen/arch/arm/include/asm/new_vgic.h
index 1e762138939f..6f7af0e02b2b 100644
--- a/xen/arch/arm/include/asm/new_vgic.h
+++ b/xen/arch/arm/include/asm/new_vgic.h
@@ -155,7 +155,7 @@ struct vgic_dist {
 };
 
 struct vgic_cpu {
-    struct vgic_irq private_irqs[VGIC_NR_PRIVATE_IRQS];
+    struct vgic_irq *private_irqs;
 
     struct list_head ap_list_head;
     spinlock_t ap_list_lock;    /* Protects the ap_list */
diff --git a/xen/arch/arm/vgic/vgic-init.c b/xen/arch/arm/vgic/vgic-init.c
index aef526f2e717..4eb49d922492 100644
--- a/xen/arch/arm/vgic/vgic-init.c
+++ b/xen/arch/arm/vgic/vgic-init.c
@@ -202,6 +202,11 @@ int vcpu_vgic_init(struct vcpu *v)
 {
     int ret = 0;
 
+    v->arch.vgic.private_irqs =
+        xzalloc_array(struct vgic_irq, VGIC_NR_PRIVATE_IRQS);
+    if ( !v->arch.vgic.private_irqs )
+        return -ENOMEM;
+
     vgic_vcpu_early_init(v);
 
     if ( gic_hw_version() == GIC_V2 )
@@ -244,6 +249,8 @@ void vcpu_vgic_free(struct vcpu *v)
     struct vgic_cpu *vgic_cpu = &v->arch.vgic;
 
     INIT_LIST_HEAD(&vgic_cpu->ap_list_head);
+
+    XFREE(v->arch.vgic.private_irqs);
 }
 
 /*
-- 
2.52.0