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Date:   Fri, 10 Nov 2017 09:20:43 +0100
From:   Christoffer Dall <cdall@linaro.org>
To:     Auger Eric <eric.auger@redhat.com>
Cc:     Marc Zyngier <marc.zyngier@arm.com>,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
        kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
        Christoffer Dall <christoffer.dall@linaro.org>,
        Shanker Donthineni <shankerd@codeaurora.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Shameerali Kolothum Thodi 
        <shameerali.kolothum.thodi@huawei.com>,
        Andre Przywara <Andre.Przywara@arm.com>
Subject: Re: [PATCH v5 09/26] KVM: arm/arm64: GICv4: Add init/teardown of the
 per-VM vPE irq domain
Message-ID: <20171110082043.GG14144@cbox>
References: <20171027142855.21584-1-marc.zyngier@arm.com>
 <20171027142855.21584-10-marc.zyngier@arm.com>
 <4a41a67d-a04b-b3ca-a5e8-c582e27c17d1@redhat.com>
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On Tue, Nov 07, 2017 at 02:08:23PM +0100, Auger Eric wrote:
> Hi Marc,
> 
> On 27/10/2017 16:28, 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.
> > 
> > The way we hook into the vgic init is slightly convoluted. We
> > 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 vgic_init and vgic_its_create.
> > 
> > Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
> > Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> > ---
> >  arch/arm/kvm/Makefile         |  1 +
> >  arch/arm64/kvm/Makefile       |  1 +
> >  include/kvm/arm_vgic.h        | 19 ++++++++++
> >  virt/kvm/arm/vgic/vgic-init.c |  9 +++++
> >  virt/kvm/arm/vgic/vgic-its.c  |  8 +++++
> >  virt/kvm/arm/vgic/vgic-v4.c   | 83 +++++++++++++++++++++++++++++++++++++++++++
> >  virt/kvm/arm/vgic/vgic.h      |  2 ++
> >  7 files changed, 123 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 ba9fb450aa1b..7eeb6c2a2f9c 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 +238,15 @@ struct vgic_dist {
> >  
> >  	/* used by vgic-debug */
> >  	struct vgic_state_iter *iter;
> > +
> > +	/*
> > +	 * GICv4 ITS per-VM data, containing the IRQ domain, the VPE
> > +	 * array, the property table pointer as well as allocation
> > +	 * data. This essentially ties the Linux IRQ core and ITS
> > +	 * together, and avoids leaking KVM's data structures anywhere
> > +	 * else.
> > +	 */
> > +	struct its_vm		its_vm;
> >  };
> >  
> >  struct vgic_v2_cpu_if {
> > @@ -254,6 +265,14 @@ struct vgic_v3_cpu_if {
> >  	u32		vgic_ap0r[4];
> >  	u32		vgic_ap1r[4];
> >  	u64		vgic_lr[VGIC_V3_MAX_LRS];
> > +
> > +	/*
> > +	 * GICv4 ITS per-VPE data, containing the doorbell IRQ, the
> > +	 * pending table pointer, the its_vm pointer and a few other
> > +	 * HW specific things. As for the its_vm structure, this is
> > +	 * linking the Linux IRQ subsystem and the ITS together.
> > +	 */
> > +	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..40be908da238 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_supports_direct_msis(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_supports_direct_msis(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 8ee03f1e89fc..89768d2b6a91 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)) {
> Don't we need to test vgic_supports_direct_msis() on this path too?
> 

Seems to me that we should, otherwise creating an ITS after the VGIC has
been initialized would fail on non-GICv4 compatible systems, right?

How about this patch as a follow-up to the series:

commit 48ec1662d0f10d6468907cdc7e12c46ca1ef497c (HEAD -> next-gicv4)
Author: Christoffer Dall <christoffer.dall@linaro.org>
Date:   Fri Nov 10 09:16:23 2017 +0100

    KVM: arm/arm64: Fix GICv4 ITS initialization issues
    
    We should only try to initialize GICv4 data structures on a GICv4
    capable system.  Move the vgic_supports_direct_msis() check inito
    vgic_v4_init() so that any KVM VGIC initialization path does not fail
    on non-GICv4 systems.
    
    Also be slightly more strict in the checking of the return value in
    vgic_its_create, and only error out on negative return values from the
    vgic_v4_init() function.  This is important because the kvm device code
    only treats negative values as errors and only cleans up in this case.
    Errornously treating a positive return value as an error from the
    vgic_v4_init() function can lead to NULL pointer dereferences, as has
    recently been observed.
    
    Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index 40be908da238..62310122ee78 100644
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -285,11 +285,9 @@ int vgic_init(struct kvm *kvm)
 	if (ret)
 		goto out;
 
-	if (vgic_supports_direct_msis(kvm)) {
-		ret = vgic_v4_init(kvm);
-		if (ret)
-			goto out;
-	}
+	ret = vgic_v4_init(kvm);
+	if (ret)
+		goto out;
 
 	kvm_for_each_vcpu(i, vcpu, kvm)
 		kvm_vgic_vcpu_enable(vcpu);
diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
index b8c1b724ba3e..c93ecd4a903b 100644
--- a/virt/kvm/arm/vgic/vgic-its.c
+++ b/virt/kvm/arm/vgic/vgic-its.c
@@ -1673,7 +1673,7 @@ static int vgic_its_create(struct kvm_device *dev, u32 type)
 
 	if (vgic_initialized(dev->kvm)) {
 		int ret = vgic_v4_init(dev->kvm);
-		if (ret) {
+		if (ret < 0) {
 			kfree(its);
 			return ret;
 		}
diff --git a/virt/kvm/arm/vgic/vgic-v4.c b/virt/kvm/arm/vgic/vgic-v4.c
index e367d65a0ebe..bb7e31fcee35 100644
--- a/virt/kvm/arm/vgic/vgic-v4.c
+++ b/virt/kvm/arm/vgic/vgic-v4.c
@@ -118,6 +118,9 @@ int vgic_v4_init(struct kvm *kvm)
 	struct kvm_vcpu *vcpu;
 	int i, nr_vcpus, ret;
 
+	if (!vgic_supports_direct_msis(kvm))
+		return 0; /* Nothing to see here... move along. */
+
 	if (dist->its_vm.vpes)
 		return 0;
 

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