From 1c91f06d296de4f0c27022f5ec464e047d471215 Mon Sep 17 00:00:00 2001 From: Alexandru Elisei Date: Tue, 1 Dec 2020 15:01:55 +0000 Subject: [PATCH] KVM: arm64: Move double-checked lock to kvm_vgic_map_resources() kvm_vgic_map_resources() is called when a VCPU if first run and it maps all the VGIC MMIO regions. To prevent double-initialization, the VGIC uses the ready variable to keep track of the state of resources and the global KVM mutex to protect against concurrent accesses. After the lock is taken, the variable is checked again in case another VCPU took the lock between the current VCPU reading ready equals false and taking the lock. The double-checked lock pattern is spread across four different functions: in kvm_vcpu_first_run_init(), in kvm_vgic_map_resource() and in vgic_{v2,v3}_map_resources(), which makes it hard to reason about and introduces minor code duplication. Consolidate the checks in kvm_vgic_map_resources(), where the lock is taken. No functional change intended. Signed-off-by: Alexandru Elisei Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20201201150157.223625-4-alexandru.elisei@arm.com --- arch/arm64/kvm/arm.c | 8 +++----- arch/arm64/kvm/vgic/vgic-init.c | 6 ++++++ arch/arm64/kvm/vgic/vgic-v2.c | 3 --- arch/arm64/kvm/vgic/vgic-v3.c | 3 --- 4 files changed, 9 insertions(+), 11 deletions(-) diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index e207e4541f552..ab782c480e9a5 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -580,11 +580,9 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu) * Map the VGIC hardware resources before running a vcpu the * first time on this VM. */ - if (unlikely(!vgic_ready(kvm))) { - ret = kvm_vgic_map_resources(kvm); - if (ret) - return ret; - } + ret = kvm_vgic_map_resources(kvm); + if (ret) + return ret; } else { /* * Tell the rest of the code that there are userspace irqchip diff --git a/arch/arm64/kvm/vgic/vgic-init.c b/arch/arm64/kvm/vgic/vgic-init.c index 32e32d67a127f..a2f4d1c85f001 100644 --- a/arch/arm64/kvm/vgic/vgic-init.c +++ b/arch/arm64/kvm/vgic/vgic-init.c @@ -428,7 +428,13 @@ int kvm_vgic_map_resources(struct kvm *kvm) struct vgic_dist *dist = &kvm->arch.vgic; int ret = 0; + if (likely(vgic_ready(kvm))) + return 0; + mutex_lock(&kvm->lock); + if (vgic_ready(kvm)) + goto out; + if (!irqchip_in_kernel(kvm)) goto out; diff --git a/arch/arm64/kvm/vgic/vgic-v2.c b/arch/arm64/kvm/vgic/vgic-v2.c index ebf53a4e12963..7f38c1a936395 100644 --- a/arch/arm64/kvm/vgic/vgic-v2.c +++ b/arch/arm64/kvm/vgic/vgic-v2.c @@ -306,9 +306,6 @@ int vgic_v2_map_resources(struct kvm *kvm) struct vgic_dist *dist = &kvm->arch.vgic; int ret = 0; - if (vgic_ready(kvm)) - goto out; - if (IS_VGIC_ADDR_UNDEF(dist->vgic_dist_base) || IS_VGIC_ADDR_UNDEF(dist->vgic_cpu_base)) { kvm_err("Need to set vgic cpu and dist addresses first\n"); diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c index 9cdf39a94a635..35029c5cb0f12 100644 --- a/arch/arm64/kvm/vgic/vgic-v3.c +++ b/arch/arm64/kvm/vgic/vgic-v3.c @@ -500,9 +500,6 @@ int vgic_v3_map_resources(struct kvm *kvm) int ret = 0; int c; - if (vgic_ready(kvm)) - goto out; - kvm_for_each_vcpu(c, vcpu, kvm) { struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu;