On Sat, 29 Jun 2019 19:09:37 +0200 Jan Kiszka <jan.kiszka@xxxxxx> wrote: Hi Jan, > Hi all, > > just got KVM running on the Raspberry Pi4. Seems they now embedded all > required logic into that new SoC. Yeah, someone saw the light and decided to enter the 21st century by attaching a GICv2 to the thing. Who knows, they may plug a GICv3 and a SMMU in 2050 at that rate! ;-) > However, as the Raspberry kernel is not yet ready for 64-bit (and > upstream is not in sight), I had to use legacy 32-bit mode. And there we > stumble over the core detection. This little patch made it work, though: > > diff --git a/arch/arm/kvm/guest.c b/arch/arm/kvm/guest.c > index 2b8de885b2bf..01606aad73cc 100644 > --- a/arch/arm/kvm/guest.c > +++ b/arch/arm/kvm/guest.c > @@ -290,6 +290,7 @@ int __attribute_const__ kvm_target_cpu(void) > case ARM_CPU_PART_CORTEX_A7: > return KVM_ARM_TARGET_CORTEX_A7; > case ARM_CPU_PART_CORTEX_A15: > + case ARM_CPU_PART_CORTEX_A72: > return KVM_ARM_TARGET_CORTEX_A15; > default: > return -EINVAL; > > That raises the question if this is hack or a valid change and if there > is general interest in mapping 64-bit cores on 32-bit if they happen to > run in 32-bit mode. The real thing to do here would be to move to a generic target, much like we did on the 64bit side. Could you investigate that instead? It would also allow KVM to be used on other 32bit cores such as A12/A17/A32. Although some would argue that the *real* real thing to do would be "rm -rf arch/arm/kvm" and be done with it, but that's a discussion for next week... ;-) > Jan > > PS: The RPi device tree lacks description of the GICH maintenance > interrupts. Seems KVM is fine without that - because it has the > information hard-coded or because it can live without that interrupt? Nah, it really should have an interrupt here. You can end-up in situation where new virtual interrupts are delayed until the next natural exit if you don't get a maintenance interrupt. Feels like a bug. Anyway, if you know of any effort to get a 64bit kernel on that thing, I'm interested in helping. I bought one on Monday, but didn't get a change to do any hacking on it just yet... Thanks, M.
