Hi Christoffer, On 17/09/17 15:43, Christoffer Dall wrote: > On Tue, Aug 08, 2017 at 05:46:08PM +0100, James Morse wrote: >> Make tpidr_el2 a cpu-offset for per-cpu variables in the same way the >> host uses tpidr_el1. This lets tpidr_el{1,2} have the same value, and >> on VHE they can be the same register. >> >> KVM calls hyp_panic() when anything unexpected happens. This may occur >> while a guest owns the EL1 registers. KVM stashes the vcpu pointer in >> tpidr_el2, which it uses to find the host context in order to restore >> the host EL1 registers before parachuting into the host's panic(). >> >> The host context is a struct kvm_cpu_context allocated in the per-cpu >> area, and mapped to hyp. Given the per-cpu offset for this CPU, this is >> easy to find. Change hyp_panic() to take a pointer to the >> struct kvm_cpu_context. Wrap these calls with an asm function that >> retrieves the struct kvm_cpu_context from the host's per-cpu area. >> >> Copy the per-cpu offset from the hosts tpidr_el1 into tpidr_el2 during >> kvm init. (Later patches will make this unnecessary for VHE hosts) >> >> We print out the vcpu pointer as part of the panic message. Add a back >> reference to the 'running vcpu' in the host cpu context to preserve this.
>> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c >> index 945e79c641c4..235d615cee30 100644 >> --- a/arch/arm64/kvm/hyp/switch.c >> +++ b/arch/arm64/kvm/hyp/switch.c >> @@ -286,9 +286,9 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu) >> u64 exit_code; >> >> vcpu = kern_hyp_va(vcpu); >> - write_sysreg(vcpu, tpidr_el2); >> >> host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context); >> + host_ctxt->__hyp_running_vcpu = vcpu; > > I'm fine with this for now, but eventually when we optimize KVM further > we may want to avoid doing this in every world-switch. One option is to > just set this pointer in vcpu_get and vcpu_load, but would it also be > possible to use the kvm_arm_running_vcpu per-cpu array directly? Yes, that would have been better, I didn't know that existed... After this point we can find per-cpu variables easily, they just need mapping to HYP. This pointer is just for the panic message, I'm not sure how useful it is. For kdump the kvm_arm_running_vcpu array holds the same information, so is printing this out just so we can spot if its totally-bogus? As your fine with this for now, I'll put tidying it up on my todo list... >> guest_ctxt = &vcpu->arch.ctxt; >> >> __sysreg_save_host_state(host_ctxt); > Reviewed-by: Christoffer Dall <cd...@linaro.org> Thanks! James _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm