Ingo Molnar <mi...@kernel.org> writes:
> * Vitaly Kuznetsov <vkuzn...@redhat.com> wrote:
>
>> Ingo Molnar <mi...@kernel.org> writes:
>>
>> > * Vitaly Kuznetsov <vkuzn...@redhat.com> wrote:
>> >
>> >> Hypervisor callback interrupts are only accounted on Xen/Hyper-V and we
>> >> detect hypervisor's type in early boot. There is no point in having
>> >> always-zero HYP: line on other hypervisors or bare metal.
>> >>
>> >> Suggested-by: Radim Krčmář <rkrc...@redhat.com>
>> >> Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
>> >> ---
>> >> arch/x86/kernel/irq.c | 13 +++++++++----
>> >> 1 file changed, 9 insertions(+), 4 deletions(-)
>> >>
>> >> diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
>> >> index 88b36648..0c82064 100644
>> >> --- a/arch/x86/kernel/irq.c
>> >> +++ b/arch/x86/kernel/irq.c
>> >> @@ -18,6 +18,7 @@
>> >> #include <asm/mce.h>
>> >> #include <asm/hw_irq.h>
>> >> #include <asm/desc.h>
>> >> +#include <asm/hypervisor.h>
>> >>
>> >> #define CREATE_TRACE_POINTS
>> >> #include <asm/trace/irq_vectors.h>
>> >> @@ -139,10 +140,14 @@ int arch_show_interrupts(struct seq_file *p, int
>> >> prec)
>> >> seq_puts(p, " Machine check polls\n");
>> >> #endif
>> >> #if IS_ENABLED(CONFIG_HYPERV) || defined(CONFIG_XEN)
>> >> - seq_printf(p, "%*s: ", prec, "HYP");
>> >> - for_each_online_cpu(j)
>> >> - seq_printf(p, "%10u ", irq_stats(j)->irq_hv_callback_count);
>> >> - seq_puts(p, " Hypervisor callback interrupts\n");
>> >> + if (x86_hyper == &x86_hyper_ms_hyperv ||
>> >> + x86_hyper == &x86_hyper_xen) {
>> >> + seq_printf(p, "%*s: ", prec, "HYP");
>> >> + for_each_online_cpu(j)
>> >> + seq_printf(p, "%10u ",
>> >> + irq_stats(j)->irq_hv_callback_count);
>> >> + seq_puts(p, " Hypervisor callback interrupts\n");
>> >> + }
>> >
>> > So I think we should simplify this to:
>> >
>> > if (x86_hyper) {
>> > ...
>> > }
>> >
>> > this will print the HYP line on hypervisors that don't use
>> > HYPERVISOR_CALLBACK_VECTOR, but it will make it a lot more
>> > self-maintaining, we
>> > won't accidentally skip this line on hypervisors that start using the
>> > callback
>> > IRQ.
>>
>> I was under an impression KVM and Vmware don't use these hypervisor
>> callback irqs 'by desing' and even if one day they start using it
>> someone will have to put inc_irq_stat() somewhere.
>>
>> If the goal is to avoid having x86_hyper_ms_hyperv/x86_hyper_xen in
>> irq.c we can follow Andrew's suggestion and add a flag
>> (use_callback_irqs?) to struct hypervisor_x86.
>
> Yeah, a flag would be nicer, and that flag should also be used somewhere else
> -
> for example in the IRQ vector init code or so?
>
> I.e. make it only possible to use the callback vector if the flag is set
> properly
> - or something like that. That way there will never be a mismatch between
> flag and
> reality.
Actually we already have the flag :-) Both Xen and Hyper-V do
alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, ...) so we can simply do
test_bit(HYPERVISOR_CALLBACK_VECTOR, used_vectors) here. It feels a
little bit hackish but it checks what we need to check.
--
Vitaly
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