On Wed, Jul 22, 2020 at 12:06:06PM +1000, Michael Ellerman wrote: > Ram Pai <linux...@us.ibm.com> writes: > > An instruction accessing a mmio address, generates a HDSI fault. This > > fault is > > appropriately handled by the Hypervisor. However in the case of secureVMs, > > the > > fault is delivered to the ultravisor. > > > > Unfortunately the Ultravisor has no correct-way to fetch the faulting > > instruction. The PEF architecture does not allow Ultravisor to enable MMU > > translation. Walking the two level page table to read the instruction can > > race > > with other vcpus modifying the SVM's process scoped page table. > > You're trying to read the guest's kernel text IIUC, that mapping should > be stable. Possibly permissions on it could change over time, but the > virtual -> real mapping should not.
Actually the code does not capture the address of the instruction in the sprg0 register. It captures the instruction itself. So should the mapping matter? > > > This problem can be correctly solved with some help from the kernel. > > > > Capture the faulting instruction in SPRG0 register, before executing the > > faulting instruction. This enables the ultravisor to easily procure the > > faulting instruction and emulate it. > > This is not something I'm going to merge. Sorry. Ok. Will consider other approaches. RP
