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Date:   Wed, 30 Aug 2017 10:50:22 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Christoffer Dall <christoffer.dall@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Eric Auger <eric.auger@...hat.com>,
        Shanker Donthineni <shankerd@...eaurora.org>,
        Mark Rutland <mark.rutland@....com>,
        Shameerali Kolothum Thodi 
        <shameerali.kolothum.thodi@...wei.com>
Subject: Re: [PATCH v3 40/59] KVM: arm/arm64: GICv4: Add init/teardown of the
 per-VM vPE irq domain

On 26/08/17 20:49, Christoffer Dall wrote:
> On Mon, Jul 31, 2017 at 06:26:18PM +0100, Marc Zyngier wrote:
>> In order to control the GICv4 view of virtual CPUs, we rely
>> on an irqdomain allocated for that purpose. Let's add a couple
>> of helpers to that effect.
>>
>> At the same time, the vgic data structures gain new fields to
>> track all this... erm... wonderful stuff.
>>
>> They way we hook into the vgic init is slightly convoluted. We
> 
> *The way ?
> 
>> need the vgic to be initialized (in order to guarantee that
>> the number of vcpus is now fixed), and we must have a vITS
>> (otherwise this is all very pointless). So we end-up calling
>> the init from both sites...
> 
> Which sites (sides ?) are those?

That's vgic_init() and  vgic_its_create().

> 
>>
>> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
>> ---
>>  arch/arm/kvm/Makefile         |  1 +
>>  arch/arm64/kvm/Makefile       |  1 +
>>  include/kvm/arm_vgic.h        |  8 +++++
>>  virt/kvm/arm/vgic/vgic-init.c |  9 ++++++
>>  virt/kvm/arm/vgic/vgic-its.c  |  8 +++++
>>  virt/kvm/arm/vgic/vgic-v4.c   | 74 +++++++++++++++++++++++++++++++++++++++++++
>>  virt/kvm/arm/vgic/vgic.h      |  2 ++
>>  7 files changed, 103 insertions(+)
>>  create mode 100644 virt/kvm/arm/vgic/vgic-v4.c
>>
>> diff --git a/arch/arm/kvm/Makefile b/arch/arm/kvm/Makefile
>> index d9beee652d36..0a1dd2cdb928 100644
>> --- a/arch/arm/kvm/Makefile
>> +++ b/arch/arm/kvm/Makefile
>> @@ -31,6 +31,7 @@ obj-y += $(KVM)/arm/vgic/vgic-init.o
>>  obj-y += $(KVM)/arm/vgic/vgic-irqfd.o
>>  obj-y += $(KVM)/arm/vgic/vgic-v2.o
>>  obj-y += $(KVM)/arm/vgic/vgic-v3.o
>> +obj-y += $(KVM)/arm/vgic/vgic-v4.o
>>  obj-y += $(KVM)/arm/vgic/vgic-mmio.o
>>  obj-y += $(KVM)/arm/vgic/vgic-mmio-v2.o
>>  obj-y += $(KVM)/arm/vgic/vgic-mmio-v3.o
>> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
>> index 5d9810086c25..c30fd388ef80 100644
>> --- a/arch/arm64/kvm/Makefile
>> +++ b/arch/arm64/kvm/Makefile
>> @@ -26,6 +26,7 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-init.o
>>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-irqfd.o
>>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-v2.o
>>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-v3.o
>> +kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-v4.o
>>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-mmio.o
>>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-mmio-v2.o
>>  kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/vgic/vgic-mmio-v3.o
>> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
>> index 84694b42373a..359eeffe9857 100644
>> --- a/include/kvm/arm_vgic.h
>> +++ b/include/kvm/arm_vgic.h
>> @@ -26,6 +26,8 @@
>>  #include <linux/list.h>
>>  #include <linux/jump_label.h>
>>  
>> +#include <linux/irqchip/arm-gic-v4.h>
>> +
>>  #define VGIC_V3_MAX_CPUS	255
>>  #define VGIC_V2_MAX_CPUS	8
>>  #define VGIC_NR_IRQS_LEGACY     256
>> @@ -236,6 +238,9 @@ struct vgic_dist {
>>  
>>  	/* used by vgic-debug */
>>  	struct vgic_state_iter *iter;
>> +
>> +	/* GICv4 ITS per-VM stuff */
> 
> I think we can do a little better in this comment.  Is it possible to
> succinctly explain the role of this field, e.g. ties together Linux IRQ
> subsystem structures with the GIC, or what the role really is.

Absolutely. I'll fix that (and the vPE field as well).

>> +	struct its_vm		its_vm;
>>  };
>>  
>>  struct vgic_v2_cpu_if {
>> @@ -254,6 +259,9 @@ struct vgic_v3_cpu_if {
>>  	u32		vgic_ap0r[4];
>>  	u32		vgic_ap1r[4];
>>  	u64		vgic_lr[VGIC_V3_MAX_LRS];
>> +
>> +	/* GICv4 vPE info */
> 
> same
> 
>> +	struct its_vpe	its_vpe;
>>  };
>>  
>>  struct vgic_cpu {
>> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
>> index 5801261f3add..d1c6c775203d 100644
>> --- a/virt/kvm/arm/vgic/vgic-init.c
>> +++ b/virt/kvm/arm/vgic/vgic-init.c
>> @@ -285,6 +285,12 @@ int vgic_init(struct kvm *kvm)
>>  	if (ret)
>>  		goto out;
>>  
>> +	if (vgic_has_its(kvm) && vgic_is_v4_capable(kvm)) {
>> +		ret = vgic_v4_init(kvm);
>> +		if (ret)
>> +			goto out;
>> +	}
>> +
>>  	kvm_for_each_vcpu(i, vcpu, kvm)
>>  		kvm_vgic_vcpu_enable(vcpu);
>>  
>> @@ -320,6 +326,9 @@ static void kvm_vgic_dist_destroy(struct kvm *kvm)
>>  
>>  	kfree(dist->spis);
>>  	dist->nr_spis = 0;
>> +
>> +	if (vgic_is_v4_capable(kvm))
>> +		vgic_v4_teardown(kvm);
>>  }
>>  
>>  void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu)
>> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
>> index fb7be8673bff..a2217f53bbe5 100644
>> --- a/virt/kvm/arm/vgic/vgic-its.c
>> +++ b/virt/kvm/arm/vgic/vgic-its.c
>> @@ -1603,6 +1603,14 @@ static int vgic_its_create(struct kvm_device *dev, u32 type)
>>  	if (!its)
>>  		return -ENOMEM;
>>  
>> +	if (vgic_initialized(dev->kvm)) {
>> +		int ret = vgic_v4_init(dev->kvm);
>> +		if (ret) {
>> +			kfree(its);
>> +			return ret;
>> +		}
>> +	}
>> +	
>>  	mutex_init(&its->its_lock);
>>  	mutex_init(&its->cmd_lock);
>>  
>> diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
>> new file mode 100644
>> index 000000000000..207e1fda0dcd
>> --- /dev/null
>> +++ b/virt/kvm/arm/vgic/vgic-v4.c
>> @@ -0,0 +1,74 @@
>> +/*
>> + * Copyright (C) 2017 ARM Ltd.
>> + * Author: Marc Zyngier <marc.zyngier@....com>
>> + *
>> + * This program is free software; you can redistribute it and/or modify
>> + * it under the terms of the GNU General Public License version 2 as
>> + * published by the Free Software Foundation.
>> + *
>> + * This program is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU General Public License
>> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>> + */
>> +
>> +#include <linux/interrupt.h>
>> +#include <linux/irqdomain.h>
>> +#include <linux/kvm_host.h>
>> +
>> +#include "vgic.h"
>> +
>> +int vgic_v4_init(struct kvm *kvm)
>> +{
>> +	struct vgic_dist *dist = &kvm->arch.vgic;
>> +	struct kvm_vcpu *vcpu;
>> +	int i, nr_vcpus, ret;
>> +
>> +	/*
>> +	 * We may be called each time a vITS is created, or when the
>> +	 * vgic is initialized. This relies on kvm->lock to be
>> +	 * held. In both cases, the number of vcpus should now be
>> +	 * fixed.
>> +	 */
> 
> I don't really see the connection between this comment and the following
> block.  Was this comment meant for the whole function?

Indeed. I'll move the comment up, and add some proper kerneldoc as well.

> 
>> +	if (dist->its_vm.vpes)
>> +		return 0;
>> +
>> +	nr_vcpus = atomic_read(&kvm->online_vcpus);
>> +
>> +	dist->its_vm.vpes = kzalloc(sizeof(*dist->its_vm.vpes) * nr_vcpus,
>> +				    GFP_KERNEL);
>> +	if (!dist->its_vm.vpes)
>> +		return -ENOMEM;
>> +
>> +	dist->its_vm.nr_vpes = nr_vcpus;
>> +
>> +	kvm_for_each_vcpu(i, vcpu, kvm)
>> +		dist->its_vm.vpes[i] = &vcpu->arch.vgic_cpu.vgic_v3.its_vpe;
>> +
>> +	ret = its_alloc_vcpu_irqs(&dist->its_vm);
>> +	if (ret < 0) {
>> +		kvm_err("VPE IRQ allocation failure\n");
>> +		kfree(dist->its_vm.vpes);
>> +		dist->its_vm.nr_vpes = 0;
>> +		dist->its_vm.vpes = NULL;
>> +		return ret;
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>> +void vgic_v4_teardown(struct kvm *kvm)
>> +{
>> +	struct its_vm *its_vm = &kvm->arch.vgic.its_vm;
>> +
>> +	if (!its_vm->vpes)
>> +		return;
>> +
>> +	its_free_vcpu_irqs(its_vm);
>> +	kfree(its_vm->vpes);
>> +	its_vm->nr_vpes = 0;
>> +	its_vm->vpes = NULL;
>> +}
>> diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
>> index 90f6436a11aa..1356f485d7cf 100644
>> --- a/virt/kvm/arm/vgic/vgic.h
>> +++ b/virt/kvm/arm/vgic/vgic.h
>> @@ -230,5 +230,7 @@ int vgic_its_resolve_lpi(struct kvm *kvm, struct vgic_its *its,
>>  struct vgic_its *vgic_msi_to_its(struct kvm *kvm, struct kvm_msi *msi);
>>  
>>  bool vgic_is_v4_capable(struct kvm *kvm);
>> +int vgic_v4_init(struct kvm *kvm);
>> +void vgic_v4_teardown(struct kvm *kvm);
>>  
>>  #endif
>> -- 
>> 2.11.0
>>
> 
> Thanks,
> -Christoffer
> 

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

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