On Tue, May 20, 2014 at 09:52:53PM +0800, Haojian Zhuang wrote:

On 20 May 2014 21:44, Christoffer Dall [off-list ref] wrote:

quoted

On Tue, May 20, 2014 at 09:10:27PM +0800, Haojian Zhuang wrote:

[...]

quoted

quoted

diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
index 47b2983..4c0c1e9 100644
--- a/virt/kvm/arm/vgic.c
+++ b/virt/kvm/arm/vgic.c

@@ -76,6 +76,8 @@
 #define IMPLEMENTER_ARM              0x43b
 #define GICC_ARCH_VERSION_V2 0x2

+#define vgic_nr_lr(vcpu)     (vcpu->hw_cfg & HWCFG_NR_LR_MASK)
+
 /* Physical address of vgic virtual cpu interface */
 static phys_addr_t vgic_vcpu_base;

@@ -97,7 +99,7 @@ static void vgic_retire_disabled_irqs(struct kvm_vcpu *vcpu);
 static void vgic_update_state(struct kvm *kvm);
 static void vgic_kick_vcpus(struct kvm *kvm);
 static void vgic_dispatch_sgi(struct kvm_vcpu *vcpu, u32 reg);
-static u32 vgic_nr_lr;
+static u32 vgic_hw_cfg;

 static unsigned int vgic_maint_irq;

@@ -624,9 +626,9 @@ static void vgic_unqueue_irqs(struct kvm_vcpu *vcpu)
      struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;
      int vcpu_id = vcpu->vcpu_id;
      int i, irq, source_cpu;
-     u32 *lr;
+     u32 *lr, nr_lr = vgic_nr_lr(vgic_cpu);

This is static for any system post-boot, right?  Can't we set this
global variable once like we did before instead of having to define
these extra variables and do the bit manipulation all over the place?

-Christoffer

I tried to define a global gich_apr variable before. But Marc didn't agree on
that. He suggested to use vgic_cpu_nr_lr to save both GICH_APR offset
and nr_lr.

Adding gich_apr variable should be the simpler implementation.

You're talking about storing this information on the vgic_cpu struct,
which is accessed on every world-switch patch.  There, you don't want
two memory accesses.

Here, on the other hand, you're in host kernel land, and you can do your
bit-shuffling once, and always access a single static variable like we
did before, which will simplify the C-code.

Makes sense?

-Christoffer