On Aug 9, 2011, at 1:17 PM, Avi Kivity wrote:
> On 08/06/2011 01:39 PM, Christoffer Dall wrote:
>> Adds a new important function in the main KVM/ARM code called
>> handle_exit() which is called from kvm_arch_vcpu_ioctl_run() on returns
>> from guest execution. This function examines the Hyp-Syndrome-Register
>> (HSR), which contains information telling KVM what caused the exit from
>> the guest.
>>
>> Some of the reasons for an exit are CP15 accesses, which are
>> not allowed from the guest and this commits handles these exits by
>> emulating the intented operation in software and skip the guest
>> instruction.
>>
>>
>> /**
>> * kvm_arch_vcpu_ioctl_run - the main VCPU run function to execute guest code
>> * @vcpu: The VCPU pointer
>> @@ -339,6 +396,26 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>> kvm_guest_exit();
>> debug_ws_exit(vcpu->arch.regs.pc);
>> trace_kvm_exit(vcpu->arch.regs.pc);
>> +
>> + ret = handle_exit(vcpu, run, ret);
>> + if (ret) {
>> + kvm_err(ret, "Error in handle_exit");
>> + break;
>> + }
>> +
>> + if (run->exit_reason == KVM_EXIT_MMIO)
>> + break;
>> +
>> + if (need_resched()) {
>> + vcpu_put(vcpu);
>> + schedule();
>> + vcpu_load(vcpu);
>> + }
>
> Preempt notifiers mean you don't need vcpu_put()/vcpu_load() - the scheduler will call kvm_arch_vcpu_put/load() automatically during context switch.
cool. thanks.
>
>> +
>> + if (signal_pending(current)&& !(run->exit_reason)) {
>> + run->exit_reason = KVM_EXIT_IRQ_WINDOW_OPEN;
>> + break;
>> + }
>> }
>
> You're supposed to return -EINTR on a signal. run->exit_reason isn't defined in this case, but traditionally we return KVM_EXIT_INTR (which means host signal, not guest signal - yes it's confusing).
thanks for clearing that up.
>
>> +
>> +/**
>> + * emulate_cp15_c15_access -- emulates cp15 accesses for CRn == 15
>> + * @vcpu: The VCPU pointer
>> + * @p: The coprocessor parameters struct pointer holding trap inst. details
>> + *
>> + * The CP15 c15 register is implementation defined, but some guest kernels
>> + * attempt to read/write a diagnostics register here. We always return 0 and
>> + * ignore writes and hope for the best. This may need to be refined.
>> + */
>> +static int emulate_cp15_c15_access(struct kvm_vcpu *vcpu,
>> + struct coproc_params *p)
>> +{
>> + trace_kvm_emulate_cp15_imp(p->Op1, p->Rt1, p->CRn, p->CRm,
>> + p->Op2, p->is_write);
>
> _imp?
implementation defined co-processor 15 operations. Took me 10 minutes to dig out from memory, so, ok, this is not super informative or clear:) Will try to come up with something better or the right comment somewhere or something.
>
>> +
>> + if (!p->is_write)
>> + *vcpu_reg(vcpu, p->Rt1) = 0;
>> +
>> + return 0;
>> +}
>> +
>>
>
> --
> error compiling committee.c: too many arguments to function
>
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