Hi Alexandru,
On 12/1/20 4:01 PM, Alexandru Elisei wrote:
> 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 <alexandru.elisei@xxxxxxx>
> ---
> 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 9d69d2bf6943..65a5e89f5133 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -530,11 +530,9 @@ 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 32e32d67a127..a2f4d1c85f00 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;
> +
While we are at it, the setting of dist->ready may be moved in
kvm_vgic_map_resources() too.
Thanks
Eric
> 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 ebf53a4e1296..7f38c1a93639 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 9cdf39a94a63..35029c5cb0f1 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;
>
>
_______________________________________________
kvmarm mailing list
kvmarm@xxxxxxxxxxxxxxxxxxxxx
https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
