On 05/03/18 14:01, Peter Maydell wrote: > Hi; I've just noticed a bug in QEMU where we weren't migrating > Secure-bank register state for AArch32 emulated guest correctly, which > turns out to be intertwined with how KVM defines its index values for > cp15 registers in the KVM_REG_ARM_* encoding. > > The problem is that QEMU defines the on-the-wire migration format > for system registers using the KVM encoding. This is fine when we're > using KVM (because all guest visible registers for KVM are non-secure), > but if we're using emulation, we might have to migrate both secure and > non-secure register state, so we need to be able to define ID values > that distinguish them. > > I could just borrow a currently-spare bit in the encoding to indicate > S/NS, but this seems liable to future breakage if the bit gets defined > to have some meaning for the kernel, so it would be nice if we could > define a bit officially, something like: > > #define KVM_REG_ARM_SECURE_MASK 0x0000000010000000 > > in arch/arm/include/uapi/asm/kvm.h > > Does this seem like a good idea? (We could alternatively steal a bit > from the top of the rather-over-specified 12 bit field for copro > number, but AFAIK bit 28 isn't used currently so is free.) I guess that'd be fine. If we ever have KVM running in S-EL2 on a v8.4 core, we'd be able to make use of this bit. Let's hope it never happens though. Would you be able to write a patch for this please? Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
