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    SubjectRe: [PATCH v3 11/12] KVM: arm/arm64: Implement KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION
    On Fri, Apr 13, 2018 at 10:20:57AM +0200, Eric Auger wrote:
    > Now all the internals are ready to handle multiple redistributor
    > regions, let's allow the userspace to register them.
    >
    > Signed-off-by: Eric Auger <eric.auger@redhat.com>
    >
    > ---
    >
    > v2 -> v3:
    > - early exit if vgic_v3_rdist_region_from_index() fails
    > ---
    > virt/kvm/arm/vgic/vgic-kvm-device.c | 42 +++++++++++++++++++++++++++++++++++--
    > virt/kvm/arm/vgic/vgic-mmio-v3.c | 4 ++--
    > virt/kvm/arm/vgic/vgic.h | 9 +++++++-
    > 3 files changed, 50 insertions(+), 5 deletions(-)
    >
    > diff --git a/virt/kvm/arm/vgic/vgic-kvm-device.c b/virt/kvm/arm/vgic/vgic-kvm-device.c
    > index e7b5a86..00e03d3 100644
    > --- a/virt/kvm/arm/vgic/vgic-kvm-device.c
    > +++ b/virt/kvm/arm/vgic/vgic-kvm-device.c
    > @@ -65,7 +65,8 @@ int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 *addr, bool write)
    > {
    > int r = 0;
    > struct vgic_dist *vgic = &kvm->arch.vgic;
    > - phys_addr_t *addr_ptr, alignment;
    > + phys_addr_t *addr_ptr = NULL;
    > + phys_addr_t alignment;
    > uint64_t undef_value = VGIC_ADDR_UNDEF;

    nit: mussed this one before, type should be u64

    >
    > mutex_lock(&kvm->lock);
    > @@ -92,7 +93,7 @@ int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 *addr, bool write)
    > if (r)
    > break;
    > if (write) {
    > - r = vgic_v3_set_redist_base(kvm, *addr);
    > + r = vgic_v3_set_redist_base(kvm, 0, *addr, 0);
    > goto out;
    > }
    > rdreg = list_first_entry(&vgic->rd_regions,
    > @@ -103,6 +104,42 @@ int kvm_vgic_addr(struct kvm *kvm, unsigned long type, u64 *addr, bool write)
    > addr_ptr = &rdreg->base;
    > break;
    > }
    > + case KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION:
    > + {
    > + struct vgic_redist_region *rdreg;
    > + uint8_t index;
    > +

    we tend to use u8, u32, etc. in the kernel.

    > + r = vgic_check_type(kvm, KVM_DEV_TYPE_ARM_VGIC_V3);
    > + if (r)
    > + break;
    > +
    > + index = *addr & KVM_VGIC_V3_RDIST_INDEX_MASK;
    > +
    > + if (write) {
    > + gpa_t base = *addr & KVM_VGIC_V3_RDIST_BASE_MASK;
    > + uint32_t count = (*addr & KVM_VGIC_V3_RDIST_COUNT_MASK)
    > + >> KVM_VGIC_V3_RDIST_COUNT_SHIFT;
    > + uint8_t flags = (*addr & KVM_VGIC_V3_RDIST_FLAGS_MASK)
    > + >> KVM_VGIC_V3_RDIST_FLAGS_SHIFT;
    > +
    > + if (!count || flags)
    > + r = -EINVAL;
    > + else
    > + r = vgic_v3_set_redist_base(kvm, index,
    > + base, count);
    > + goto out;
    > + }
    > +
    > + rdreg = vgic_v3_rdist_region_from_index(kvm, index);
    > + if (!rdreg) {
    > + r = -ENODEV;
    > + goto out;
    > + }
    > +
    > + *addr_ptr = rdreg->base & index &
    > + (uint64_t)rdreg->count << KVM_VGIC_V3_RDIST_COUNT_SHIFT;

    This looks fairly broken, isn't this a clear null pointer dereference?

    (If we're making this ioctl read-only using the parameter as both in/out
    for set/get, that should also be documented in the API text, then you
    should consider writing a small test along with your userspace
    implementation to actually test that functionality - otherwise we should
    just make this write-only and omit the index part. It could be said
    that retrieving what the kernel actually has is a reasonable debug
    feature.)

    I think you want (notice the | instead of & as well):

    *addr = index;
    *addr |= rdreg->base;
    *addr |= (u64)rdreg->count << KVM_VGIC_V3_RDIST_COUNT_SHIFT;
    goto out;

    It is then debatable if the addr_ptr construct gets too convoluted when
    not used in every case, and if the logic should be embedded into each
    case, and the addr_ptr variable dropped. Meh, I don't mind leaving it
    for now.


    > + break;
    > + }
    > default:
    > r = -ENODEV;
    > }
    > @@ -674,6 +711,7 @@ static int vgic_v3_has_attr(struct kvm_device *dev,
    > switch (attr->attr) {
    > case KVM_VGIC_V3_ADDR_TYPE_DIST:
    > case KVM_VGIC_V3_ADDR_TYPE_REDIST:
    > + case KVM_VGIC_V3_ADDR_TYPE_REDIST_REGION:
    > return 0;
    > }
    > break;
    > diff --git a/virt/kvm/arm/vgic/vgic-mmio-v3.c b/virt/kvm/arm/vgic/vgic-mmio-v3.c
    > index df23e66..f603fdf 100644
    > --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c
    > +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c
    > @@ -770,11 +770,11 @@ static int vgic_v3_insert_redist_region(struct kvm *kvm, uint32_t index,
    > return ret;
    > }
    >
    > -int vgic_v3_set_redist_base(struct kvm *kvm, u64 addr)
    > +int vgic_v3_set_redist_base(struct kvm *kvm, u32 index, u64 addr, u32 count)
    > {
    > int ret;
    >
    > - ret = vgic_v3_insert_redist_region(kvm, 0, addr, 0);
    > + ret = vgic_v3_insert_redist_region(kvm, index, addr, count);
    > if (ret)
    > return ret;
    >
    > diff --git a/virt/kvm/arm/vgic/vgic.h b/virt/kvm/arm/vgic/vgic.h
    > index 95b8345..0a95b43 100644
    > --- a/virt/kvm/arm/vgic/vgic.h
    > +++ b/virt/kvm/arm/vgic/vgic.h
    > @@ -96,6 +96,13 @@
    > /* we only support 64 kB translation table page size */
    > #define KVM_ITS_L1E_ADDR_MASK GENMASK_ULL(51, 16)
    >
    > +#define KVM_VGIC_V3_RDIST_INDEX_MASK GENMASK_ULL(11, 0)
    > +#define KVM_VGIC_V3_RDIST_FLAGS_MASK GENMASK_ULL(15, 12)
    > +#define KVM_VGIC_V3_RDIST_FLAGS_SHIFT 12
    > +#define KVM_VGIC_V3_RDIST_BASE_MASK GENMASK_ULL(51, 16)
    > +#define KVM_VGIC_V3_RDIST_COUNT_MASK GENMASK_ULL(63, 52)
    > +#define KVM_VGIC_V3_RDIST_COUNT_SHIFT 52
    > +
    > /* Requires the irq_lock to be held by the caller. */
    > static inline bool irq_is_pending(struct vgic_irq *irq)
    > {
    > @@ -201,7 +208,7 @@ int vgic_v3_probe(const struct gic_kvm_info *info);
    > int vgic_v3_map_resources(struct kvm *kvm);
    > int vgic_v3_lpi_sync_pending_status(struct kvm *kvm, struct vgic_irq *irq);
    > int vgic_v3_save_pending_tables(struct kvm *kvm);
    > -int vgic_v3_set_redist_base(struct kvm *kvm, u64 addr);
    > +int vgic_v3_set_redist_base(struct kvm *kvm, u32 index, u64 addr, u32 count);
    > int vgic_register_redist_iodev(struct kvm_vcpu *vcpu);
    > bool vgic_v3_check_base(struct kvm *kvm);
    >
    > --
    > 2.5.5
    >

    Thanks,
    -Christoffer

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