Re: [RFC PATCH 09/11] kvm: simplify processor compat check

Il 27/09/2013 15:13, Aneesh Kumar K.V ha scritto:

Alexander Graf [off-list ref] writes:

quoted

On 27.09.2013, at 12:03, Aneesh Kumar K.V wrote:

quoted

From: "Aneesh Kumar K.V" <redacted>

Missing patch description.

quoted

Signed-off-by: Aneesh Kumar K.V <redacted>

I fail to see how this really simplifies things, but at the end of the
day it's Gleb's and Paolo's call.

will do. It avoid calling 

	for_each_online_cpu(cpu) {
		smp_call_function_single() 

on multiple architecture.

I agree with Alex.

The current code is not specially awesome; having
kvm_arch_check_processor_compat take an int* disguised as a void* is a
bit ugly indeed.

However, the API makes sense and tells you that it is being passed as a
callback (to smp_call_function_single in this case).

You are making the API more complicated to use on the arch layer
(because arch maintainers now have to think "do I need to check this on
all online CPUs?") and making the "leaf" POWER code less legible because
it still has the weird void()(void *) calling convention.

If anything, you could change kvm_arch_check_processor_compat to return
an int and accept no argument, and introduce a wrapper that kvm_init
passes to smp_call_function_single.

Paolo

We also want to make the smp call function a callback of opaque. Hence
this should be made arch specific. 

int kvm_arch_check_processor_compat(void *opaque)
{
	int r,cpu;
	struct kvmppc_ops *kvm_ops = (struct kvmppc_ops *)opaque;
	for_each_online_cpu(cpu) {
		smp_call_function_single(cpu,
					 kvm_ops->check_processor_compat,
					 &r, 1);
		if (r < 0)
			break;
	}
	return r;
}

against

-	for_each_online_cpu(cpu) {
-		smp_call_function_single(cpu,
-				kvm_arch_check_processor_compat,
-				&r, 1);
-		if (r < 0)
-			goto out_free_1;
-	}
+
+	r = kvm_arch_check_processor_compat(opaque);
+	if (r < 0)
+		goto out_free_1;

quoted

Which brings me to the next issue: You forgot to CC kvm@vger on your
patch set. Gleb and Paolo don't read kvm-ppc@vger. And they shouldn't
have to. Every kvm patch that you want review on or that should get
applied needs to be sent to kvm@vger. If you want to tag it as PPC
specific patch, do so by CC'ing kvm-ppc@vger.

Will do in the next update

-aneesh