Re: [PATCH v5 09/26] KVM: arm/arm64: GICv4: Add init/teardown of the per-VM vPE irq domain

Christoffer Dall
2017-11-10T08:18:39Z

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;