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KVM: arm/arm64: vgic-v2: Avoid accessing GICH registers 

GICv2 registers are *slow*. As in "terrifyingly slow". Which is bad.
But we're equaly bad, as we make a point in accessing them even if
we don't have any interrupt in flight.

A good solution is to first find out if we have anything useful to
write into the GIC, and if we don't, to simply not do it. This
involves tracking which LRs actually have something valid there.

Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Marc Zyngier 2016-02-02 19:35:34 +00:00
parent 9b4a300443
commit 59f00ff9af
2 changed files with 52 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/kvm/arm_vgic.h
View File

@ -321,6 +321,8 @@ struct vgic_cpu {
/* Protected by the distributor's irq_phys_map_lock */
struct list_head irq_phys_map_list;
u64 live_lrs;
};
#define LR_EMPTY 0xff

46
virt/kvm/arm/hyp/vgic-v2-sr.c
View File

@ -36,15 +36,20 @@ void __hyp_text __vgic_v2_save_state(struct kvm_vcpu *vcpu)
nr_lr = vcpu->arch.vgic_cpu.nr_lr;
cpu_if->vgic_vmcr = readl_relaxed(base + GICH_VMCR);
cpu_if->vgic_misr = readl_relaxed(base + GICH_MISR);
if (vcpu->arch.vgic_cpu.live_lrs) {
eisr0 = readl_relaxed(base + GICH_EISR0);
elrsr0 = readl_relaxed(base + GICH_ELRSR0);
cpu_if->vgic_misr = readl_relaxed(base + GICH_MISR);
cpu_if->vgic_apr = readl_relaxed(base + GICH_APR);
if (unlikely(nr_lr > 32)) {
eisr1 = readl_relaxed(base + GICH_EISR1);
elrsr1 = readl_relaxed(base + GICH_ELRSR1);
} else {
eisr1 = elrsr1 = 0;
}
#ifdef CONFIG_CPU_BIG_ENDIAN
cpu_if->vgic_eisr = ((u64)eisr0 << 32) | eisr1;
cpu_if->vgic_elrsr = ((u64)elrsr0 << 32) | elrsr1;
@ -52,12 +57,20 @@ void __hyp_text __vgic_v2_save_state(struct kvm_vcpu *vcpu)
cpu_if->vgic_eisr = ((u64)eisr1 << 32) | eisr0;
cpu_if->vgic_elrsr = ((u64)elrsr1 << 32) | elrsr0;
#endif
cpu_if->vgic_apr = readl_relaxed(base + GICH_APR);
for (i = 0; i < nr_lr; i++)
if (vcpu->arch.vgic_cpu.live_lrs & (1UL << i))
cpu_if->vgic_lr[i] = readl_relaxed(base + GICH_LR0 + (i * 4));
writel_relaxed(0, base + GICH_HCR);
for (i = 0; i < nr_lr; i++)
cpu_if->vgic_lr[i] = readl_relaxed(base + GICH_LR0 + (i * 4));
vcpu->arch.vgic_cpu.live_lrs = 0;
} else {
cpu_if->vgic_eisr = 0;
cpu_if->vgic_elrsr = ~0UL;
cpu_if->vgic_misr = 0;
cpu_if->vgic_apr = 0;
}
}
/* vcpu is already in the HYP VA space */
@ -68,15 +81,30 @@ void __hyp_text __vgic_v2_restore_state(struct kvm_vcpu *vcpu)
struct vgic_dist *vgic = &kvm->arch.vgic;
void __iomem *base = kern_hyp_va(vgic->vctrl_base);
int i, nr_lr;
u64 live_lrs = 0;
if (!base)
return;
writel_relaxed(cpu_if->vgic_hcr, base + GICH_HCR);
writel_relaxed(cpu_if->vgic_vmcr, base + GICH_VMCR);
writel_relaxed(cpu_if->vgic_apr, base + GICH_APR);
nr_lr = vcpu->arch.vgic_cpu.nr_lr;
for (i = 0; i < nr_lr; i++)
writel_relaxed(cpu_if->vgic_lr[i], base + GICH_LR0 + (i * 4));
if (cpu_if->vgic_lr[i] & GICH_LR_STATE)
live_lrs |= 1UL << i;
if (live_lrs) {
writel_relaxed(cpu_if->vgic_hcr, base + GICH_HCR);
writel_relaxed(cpu_if->vgic_apr, base + GICH_APR);
for (i = 0; i < nr_lr; i++) {
u32 val = 0;
if (live_lrs & (1UL << i))
val = cpu_if->vgic_lr[i];
writel_relaxed(val, base + GICH_LR0 + (i * 4));
}
}
writel_relaxed(cpu_if->vgic_vmcr, base + GICH_VMCR);
vcpu->arch.vgic_cpu.live_lrs = live_lrs;
}