KVM: arm/arm64: Fix bug when registering redist iodevs

If userspace creates the VCPUs after initializing the VGIC, then we end
up in a situation where we trigger a bug in kvm_vcpu_get_idx(), because
it is called prior to adding the VCPU into the vcpus array on the VM.

There is no tight coupling between the VCPU index and the area of the
redistributor region used for the VCPU, so we can simply ensure that all
creations of redistributors are serialized per VM, and increment an
offset when we successfully add a redistributor.

The vgic_register_redist_iodev() function can be called from two paths:
vgic_redister_all_redist_iodev() which is called via the kvm_vgic_addr()
device attribute handler.  This patch already holds the kvm->lock mutex.

The other path is via kvm_vgic_vcpu_init, which is called through a
longer chain from kvm_vm_ioctl_create_vcpu(), which releases the
kvm->lock mutex just before calling kvm_arch_vcpu_create(), so we can
simply take this mutex again later for our purposes.

Fixes: ab6f468c10 ("KVM: arm/arm64: Register iodevs when setting redist base and creating VCPUs")
Signed-off-by: Christoffer Dall <cdall@linaro.org>
Tested-by: Jean-Philippe Brucker <jean-philippe.brucker@arm.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
index 97b8d3728b3103f1b54f711f15d06fa84691e372..ef718586321ce0dea03aabe8b114beca9cb71a74 100644 (file)
--- a/include/kvm/arm_vgic.h
+++ b/include/kvm/arm_vgic.h
@@ -195,7 +195,10 @@ struct vgic_dist {
                /* either a GICv2 CPU interface */
                gpa_t                   vgic_cpu_base;
                /* or a number of GICv3 redistributor regions */
-               gpa_t                   vgic_redist_base;
+               struct {
+                       gpa_t           vgic_redist_base;
+                       gpa_t           vgic_redist_free_offset;
+               };
        };
 
        /* distributor enabled */

diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
index dc68e2e424abf301151f4a610d412ea4b9109831..3a0b8999f011c6e3e1ff6ea7699577879a651fd3 100644 (file)
--- a/virt/kvm/arm/vgic/vgic-init.c
+++ b/virt/kvm/arm/vgic/vgic-init.c
@@ -242,8 +242,11 @@ int kvm_vgic_vcpu_init(struct kvm_vcpu *vcpu)
         * If we are creating a VCPU with a GICv3 we must also register the
         * KVM io device for the redistributor that belongs to this VCPU.
         */
-       if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3)
+       if (dist->vgic_model == KVM_DEV_TYPE_ARM_VGIC_V3) {
+               mutex_lock(&vcpu->kvm->lock);
                ret = vgic_register_redist_iodev(vcpu);
+               mutex_unlock(&vcpu->kvm->lock);
+       }
        return ret;
 }
 

diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c
index 99da1a207c19b0563030bf4ad842d8d805b1b153..9b0f6810e7a87405d2de47c33ec3ebca51de3bab 100644 (file)
--- a/virt/kvm/arm/vgic/vgic-mmio-v3.c
+++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c
@@ -586,7 +586,7 @@ int vgic_register_redist_iodev(struct kvm_vcpu *vcpu)
        if (!vgic_v3_check_base(kvm))
                return -EINVAL;
 
-       rd_base = vgic->vgic_redist_base + kvm_vcpu_get_idx(vcpu) * SZ_64K * 2;
+       rd_base = vgic->vgic_redist_base + vgic->vgic_redist_free_offset;
        sgi_base = rd_base + SZ_64K;
 
        kvm_iodevice_init(&rd_dev->dev, &kvm_io_gic_ops);
@@ -615,11 +615,14 @@ int vgic_register_redist_iodev(struct kvm_vcpu *vcpu)
        ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, sgi_base,
                                      SZ_64K, &sgi_dev->dev);
        mutex_unlock(&kvm->slots_lock);
-       if (ret)
+       if (ret) {
                kvm_io_bus_unregister_dev(kvm, KVM_MMIO_BUS,
                                          &rd_dev->dev);
+               return ret;
+       }
 
-       return ret;
+       vgic->vgic_redist_free_offset += 2 * SZ_64K;
+       return 0;
 }
 
 static void vgic_unregister_redist_iodev(struct kvm_vcpu *vcpu)