On 25.02.2012, at 00:40, Scott Wood wrote:
> On 02/24/2012 08:26 AM, Alexander Graf wrote:
>> +static void kvmppc_fill_pt_regs(struct kvm_vcpu *vcpu, struct pt_regs *regs)
>> {
>> - int r = RESUME_HOST;
>> + int i;
>>
>> - /* update before a new last_exit_type is rewritten */
>> - kvmppc_update_timing_stats(vcpu);
>> + for (i = 0; i < 32; i++)
>> + regs->gpr[i] = kvmppc_get_gpr(vcpu, i);
>> + regs->nip = vcpu->arch.pc;
>> + regs->msr = vcpu->arch.shared->msr;
>> + regs->ctr = vcpu->arch.ctr;
>> + regs->link = vcpu->arch.lr;
>> + regs->xer = kvmppc_get_xer(vcpu);
>> + regs->ccr = kvmppc_get_cr(vcpu);
>> + regs->dar = get_guest_dear(vcpu);
>> + regs->dsisr = get_guest_esr(vcpu);
>> +}
>
> How much overhead does this add to every interrupt? Can't we keep this
> to the minimum that perf cares about?
I would rather not make assumptions on what perf cares about - maybe we want to
one day implement "perf kvm" and then perf could rely on pretty much anything
in there.
>
>> +
>> +static void kvmppc_restart_interrupt(struct kvm_vcpu *vcpu,
>> + unsigned int exit_nr)
>> +{
>> + struct pt_regs regs = *current->thread.regs;
>>
>> + kvmppc_fill_pt_regs(vcpu, ®s);
>
> Why are you copying out of current->thread.regs? That's old junk data,
> set by some previous exception and possibly overwritten since.
Because it gives us good default values for anything we don't set. Do you have
other recommendations?
Alex
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