On Sun, Sep 29, 2013 at 08:35:16PM +0530, Aneesh Kumar K.V wrote:
> Gleb Natapov <gleb@xxxxxxxxxx> writes:
>
> > On Sat, Sep 28, 2013 at 09:06:47PM +0530, Aneesh Kumar K.V wrote:
> >> Paolo Bonzini <pbonzini@xxxxxxxxxx> writes:
> >>
> >> > Il 27/09/2013 15:13, Aneesh Kumar K.V ha scritto:
> >> >> Alexander Graf <agraf@xxxxxxx> writes:
> >> >>
> >> >>> On 27.09.2013, at 12:03, Aneesh Kumar K.V wrote:
> >> >>>
> >> >>>> From: "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> >> >>>
> >> >>> Missing patch description.
> >> >>>
> >> >>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
> >> >>>
> >> >>> 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).
> >>
> >> But whether to check on all cpus or not is arch dependent right?.
> >> IIUC only x86 and ppc64 need to do that. Also on ppc64 it really
> >> depends on whether HV or PR. We need to check on all cpus only if it is
> >> HV.
> >>
> >> >
> >> > 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.
> >> >
> >>
> >> IIUC what we wanted to check is to find out whether kvm can run on this
> >> system. That is really an arch specific check. So for core kvm the call
> >> should be a simple
> >>
> >> if (kvm_arch_check_process_compat() < 0)
> >> error;
> > We have that already, just return error from kvm_arch_hardware_setup. This
> > is specific processor compatibility check and you are arguing that the
> > processor check should be part of kvm_arch_hardware_setup().
>
>
> What about the success case ?. ie, on arch like arm we do
>
> void kvm_arch_check_processor_compat(void *rtn)
> {
> *(int *)rtn = 0;
> }
>
> for_each_online_cpu(cpu) {
As I said they opted out from doing the check. They may reconsider after
first bad HW will be discovered.
> smp_call_function_single(cpu,
> kvm_arch_check_processor_compat,
> &r, 1);
> if (r < 0)
> goto out_free_1;
> }
>
> There is no need to do that for loop for arm.
It's done once during module initialisation. Why is this a big deal?
--
Gleb.
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