From: Zenghui Yu <yuzenghui@xxxxxxxxxx> commit 23bde34771f1ea92fb5e6682c0d8c04304d34b3b upstream. It was recently reported that if GICR_TYPER is accessed before the RD base address is set, we'll suffer from the unset @rdreg dereferencing. Oops... gpa_t last_rdist_typer = rdreg->base + GICR_TYPER + (rdreg->free_index - 1) * KVM_VGIC_V3_REDIST_SIZE; It's "expected" that users will access registers in the redistributor if the RD has been properly configured (e.g., the RD base address is set). But it hasn't yet been covered by the existing documentation. Per discussion on the list [1], the reporting of the GICR_TYPER.Last bit for userspace never actually worked. And it's difficult for us to emulate it correctly given that userspace has the flexibility to access it any time. Let's just drop the reporting of the Last bit for userspace for now (userspace should have full knowledge about it anyway) and it at least prevents kernel from panic ;-) [1] https://lore.kernel.org/kvmarm/c20865a267e44d1e2c0d52ce4e012263@xxxxxxxxxx/ Fixes: ba7b3f1275fd ("KVM: arm/arm64: Revisit Redistributor TYPER last bit computation") Reported-by: Keqian Zhu <zhukeqian1@xxxxxxxxxx> Signed-off-by: Zenghui Yu <yuzenghui@xxxxxxxxxx> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx> Link: https://lore.kernel.org/r/20201117151629.1738-1-yuzenghui@xxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- virt/kvm/arm/vgic/vgic-mmio-v3.c | 22 ++++++++++++++++++++-- 1 file changed, 20 insertions(+), 2 deletions(-) --- a/virt/kvm/arm/vgic/vgic-mmio-v3.c +++ b/virt/kvm/arm/vgic/vgic-mmio-v3.c @@ -226,6 +226,23 @@ static unsigned long vgic_mmio_read_v3r_ return extract_bytes(value, addr & 7, len); } +static unsigned long vgic_uaccess_read_v3r_typer(struct kvm_vcpu *vcpu, + gpa_t addr, unsigned int len) +{ + unsigned long mpidr = kvm_vcpu_get_mpidr_aff(vcpu); + int target_vcpu_id = vcpu->vcpu_id; + u64 value; + + value = (u64)(mpidr & GENMASK(23, 0)) << 32; + value |= ((target_vcpu_id & 0xffff) << 8); + + if (vgic_has_its(vcpu->kvm)) + value |= GICR_TYPER_PLPIS; + + /* reporting of the Last bit is not supported for userspace */ + return extract_bytes(value, addr & 7, len); +} + static unsigned long vgic_mmio_read_v3r_iidr(struct kvm_vcpu *vcpu, gpa_t addr, unsigned int len) { @@ -532,8 +549,9 @@ static const struct vgic_register_region REGISTER_DESC_WITH_LENGTH(GICR_IIDR, vgic_mmio_read_v3r_iidr, vgic_mmio_write_wi, 4, VGIC_ACCESS_32bit), - REGISTER_DESC_WITH_LENGTH(GICR_TYPER, - vgic_mmio_read_v3r_typer, vgic_mmio_write_wi, 8, + REGISTER_DESC_WITH_LENGTH_UACCESS(GICR_TYPER, + vgic_mmio_read_v3r_typer, vgic_mmio_write_wi, + vgic_uaccess_read_v3r_typer, vgic_mmio_uaccess_write_wi, 8, VGIC_ACCESS_64bit | VGIC_ACCESS_32bit), REGISTER_DESC_WITH_LENGTH(GICR_WAKER, vgic_mmio_read_raz, vgic_mmio_write_wi, 4,
