When a guest accesses memory outside the memory slots, KVM usually bounces the access back to userspace with KVM_EXIT_MMIO. However, on arm/arm64 systems, certain load/store instructions did not provide decoding info for the hypervisor to emulate the instruction, and in this case KVM has rather rudely returned -ENOSYS and printed a not overly helpful error message: load/store instruction decoding not implemented This patch series improves the error message and allows userspace to be notified of this event instead of receiving -ENOSYS, and also allows userspace to ask KVM to inject an external abort to the guest, which it can use for any memory access that it either cannot handle. One remaining case which this patch set does not address is if the guest accesses an in-kernel emulated device, such as the VGIC, but using a load/store instruction which doesn't provide decode info. With these patches, this will return to userspace for it to handle, but there's no way for userspace to return the decoding information to KVM and have KVM complete the access to the in-kernel emulated device. I have no plans to address this limitation. Changes since v1: - Rebased on v5.4-rc2 - Fixed some documentation and coding nit in review of v1 Christoffer Dall (2): KVM: arm/arm64: Allow reporting non-ISV data aborts to userspace KVM: arm/arm64: Allow user injection of external data aborts Documentation/virt/kvm/api.txt | 51 +++++++++++++++++++++++++++- arch/arm/include/asm/kvm_arm.h | 1 + arch/arm/include/asm/kvm_emulate.h | 5 +++ arch/arm/include/asm/kvm_host.h | 8 +++++ arch/arm/include/uapi/asm/kvm.h | 3 +- arch/arm/kvm/guest.c | 3 ++ arch/arm64/include/asm/kvm_emulate.h | 5 +++ arch/arm64/include/asm/kvm_host.h | 8 +++++ arch/arm64/include/uapi/asm/kvm.h | 3 +- arch/arm64/kvm/guest.c | 3 ++ arch/arm64/kvm/inject_fault.c | 4 +-- include/uapi/linux/kvm.h | 8 +++++ virt/kvm/arm/arm.c | 22 ++++++++++++ virt/kvm/arm/mmio.c | 9 ++++- 14 files changed, 127 insertions(+), 6 deletions(-) -- 2.18.0 _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
