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SubjectRE: [PATCH] KVM: x86: Add lowest-priority support for vt-d posted-interrupts
Date
Hi Paolo,

Any comments about this patch, thanks in advance!

Thanks,
Feng

> -----Original Message-----
> From: Wu, Feng
> Sent: Monday, November 9, 2015 10:47 AM
> To: pbonzini@redhat.com
> Cc: kvm@vger.kernel.org; linux-kernel@vger.kernel.org; Wu, Feng
> <feng.wu@intel.com>
> Subject: [PATCH] KVM: x86: Add lowest-priority support for vt-d posted-
> interrupts
>
> Use vector-hashing to handle lowest-priority interrupts for
> posted-interrupts. As an example, modern Intel CPUs use this
> method to handle lowest-priority interrupts.
>
> Signed-off-by: Feng Wu <feng.wu@intel.com>
> ---
> arch/x86/include/asm/kvm_host.h | 2 ++
> arch/x86/kvm/irq_comm.c | 52
> +++++++++++++++++++++++++++++++++++++
> arch/x86/kvm/lapic.c | 57
> +++++++++++++++++++++++++++++++++++++++++
> arch/x86/kvm/lapic.h | 2 ++
> arch/x86/kvm/vmx.c | 14 ++++++++--
> 5 files changed, 125 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h
> b/arch/x86/include/asm/kvm_host.h
> index 9265196..e225106 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1258,6 +1258,8 @@ bool kvm_vcpu_is_bsp(struct kvm_vcpu *vcpu);
>
> bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
> struct kvm_vcpu **dest_vcpu);
> +struct kvm_vcpu *kvm_intr_vector_hashing_dest(struct kvm *kvm,
> + struct kvm_lapic_irq *irq);
>
> void kvm_set_msi_irq(struct kvm_kernel_irq_routing_entry *e,
> struct kvm_lapic_irq *irq);
> diff --git a/arch/x86/kvm/irq_comm.c b/arch/x86/kvm/irq_comm.c
> index 84b96d3..8156e45 100644
> --- a/arch/x86/kvm/irq_comm.c
> +++ b/arch/x86/kvm/irq_comm.c
> @@ -266,6 +266,58 @@ out:
> return r;
> }
>
> +/*
> + * This routine handles lowest-priority interrupts using vector-hashing
> + * mechanism. As an example, modern Intel CPUs use this method to
> handle
> + * lowest-priority interrupts.
> + *
> + * Here is the details about the vector-hashing mechanism:
> + * 1. For lowest-priority interrupts, store all the possible destination
> + * vCPUs in an array.
> + * 2. Use "guest vector % max number of destination vCPUs" to find the
> right
> + * destination vCPU in the array for the lowest-priority interrupt.
> + */
> +struct kvm_vcpu *kvm_intr_vector_hashing_dest(struct kvm *kvm,
> + struct kvm_lapic_irq *irq)
> +
> +{
> + unsigned long
> dest_vcpu_bitmap[BITS_TO_LONGS(KVM_MAX_VCPUS)];
> + unsigned int dest_vcpus = 0;
> + struct kvm_vcpu *vcpu;
> + unsigned int i, mod, idx = 0;
> +
> + vcpu = kvm_intr_vector_hashing_dest_fast(kvm, irq);
> + if (vcpu)
> + return vcpu;
> +
> + memset(dest_vcpu_bitmap, 0, sizeof(dest_vcpu_bitmap));
> +
> + kvm_for_each_vcpu(i, vcpu, kvm) {
> + if (!kvm_apic_present(vcpu))
> + continue;
> +
> + if (!kvm_apic_match_dest(vcpu, NULL, irq->shorthand,
> + irq->dest_id, irq->dest_mode))
> + continue;
> +
> + __set_bit(vcpu->vcpu_id, dest_vcpu_bitmap);
> + dest_vcpus++;
> + }
> +
> + if (dest_vcpus == 0)
> + return NULL;
> +
> + mod = irq->vector % dest_vcpus;
> +
> + for (i = 0; i <= mod; i++) {
> + idx = find_next_bit(dest_vcpu_bitmap, KVM_MAX_VCPUS,
> idx) + 1;
> + BUG_ON(idx >= KVM_MAX_VCPUS);
> + }
> +
> + return kvm_get_vcpu(kvm, idx - 1);
> +}
> +EXPORT_SYMBOL_GPL(kvm_intr_vector_hashing_dest);
> +
> bool kvm_intr_is_single_vcpu(struct kvm *kvm, struct kvm_lapic_irq *irq,
> struct kvm_vcpu **dest_vcpu)
> {
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index ecd4ea1..4937aa4 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -816,6 +816,63 @@ out:
> return ret;
> }
>
> +struct kvm_vcpu *kvm_intr_vector_hashing_dest_fast(struct kvm *kvm,
> + struct kvm_lapic_irq *irq)
> +{
> + struct kvm_apic_map *map;
> + struct kvm_vcpu *vcpu = NULL;
> +
> + if (irq->shorthand)
> + return NULL;
> +
> + rcu_read_lock();
> + map = rcu_dereference(kvm->arch.apic_map);
> +
> + if (!map)
> + goto out;
> +
> + if ((irq->dest_mode != APIC_DEST_PHYSICAL) &&
> + kvm_lowest_prio_delivery(irq)) {
> + u16 cid;
> + int i, idx = 0;
> + unsigned long bitmap = 1;
> + unsigned int mod, dest_vcpus = 0;
> + struct kvm_lapic **dst = NULL;
> +
> +
> + if (!kvm_apic_logical_map_valid(map))
> + goto out;
> +
> + apic_logical_id(map, irq->dest_id, &cid, (u16 *)&bitmap);
> +
> + if (cid >= ARRAY_SIZE(map->logical_map))
> + goto out;
> +
> + dst = map->logical_map[cid];
> +
> + for_each_set_bit(i, &bitmap, 16) {
> + if (!dst[i])
> + continue;
> +
> + dest_vcpus++;
> + }
> +
> + mod = irq->vector % dest_vcpus;
> +
> + for (i = 0; i <= mod; i++) {
> + idx = find_next_bit(&bitmap, KVM_MAX_VCPUS, idx)
> + 1;
> + BUG_ON(idx >= KVM_MAX_VCPUS);
> + }
> +
> + if (kvm_apic_present(dst[idx-1]->vcpu))
> + vcpu = dst[idx-1]->vcpu;
> + }
> +
> +out:
> + rcu_read_unlock();
> + return vcpu;
> +}
> +
> /*
> * Add a pending IRQ into lapic.
> * Return 1 if successfully added and 0 if discarded.
> diff --git a/arch/x86/kvm/lapic.h b/arch/x86/kvm/lapic.h
> index fde8e35d..a6a775d 100644
> --- a/arch/x86/kvm/lapic.h
> +++ b/arch/x86/kvm/lapic.h
> @@ -170,4 +170,6 @@ void wait_lapic_expire(struct kvm_vcpu *vcpu);
>
> bool kvm_intr_is_single_vcpu_fast(struct kvm *kvm, struct kvm_lapic_irq
> *irq,
> struct kvm_vcpu **dest_vcpu);
> +struct kvm_vcpu *kvm_intr_vector_hashing_dest_fast(struct kvm *kvm,
> + struct kvm_lapic_irq *irq);
> #endif
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 5eb56ed..57f71ee 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -159,6 +159,9 @@ static int ple_window_actual_max =
> KVM_VMX_DEFAULT_PLE_WINDOW_MAX;
> static int ple_window_max = KVM_VMX_DEFAULT_PLE_WINDOW_MAX;
> module_param(ple_window_max, int, S_IRUGO);
>
> +static bool __read_mostly enable_pi_vector_hashing = 1;
> +module_param(enable_pi_vector_hashing, bool, S_IRUGO);
> +
> extern const ulong vmx_return;
>
> #define NR_AUTOLOAD_MSRS 8
> @@ -10702,8 +10705,15 @@ static int vmx_update_pi_irte(struct kvm *kvm,
> unsigned int host_irq,
> */
>
> kvm_set_msi_irq(e, &irq);
> - if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu))
> - continue;
> + if (!kvm_intr_is_single_vcpu(kvm, &irq, &vcpu)) {
> + if ((!enable_pi_vector_hashing ||
> + irq.delivery_mode != APIC_DM_LOWEST))
> + continue;
> +
> + vcpu = kvm_intr_vector_hashing_dest(kvm, &irq);
> + if (!vcpu)
> + continue;
> + }
>
> vcpu_info.pi_desc_addr = __pa(vcpu_to_pi_desc(vcpu));
> vcpu_info.vector = irq.vector;
> --
> 2.1.0



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