On Mon, Feb 23, 2026 at 08:49:37PM +0000, Michael Kelley wrote:
> From: Stanislav Kinsburskii <[email protected]> Sent: Monday,
> February 23, 2026 11:40 AM
> >
>
> [snip]
>
> > > +
> > > +static int __init mshv_sint_vector_init(void)
> > > +{
> > > + int ret;
> > > + struct hv_register_assoc reg = {
> > > + .name = HV_ARM64_REGISTER_SINT_RESERVED_INTERRUPT_ID,
> > > + };
> > > + union hv_input_vtl input_vtl = { 0 };
> > > +
> > > + if (acpi_disabled)
> > > + return -ENODEV;
> > > +
> > > + ret = hv_call_get_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
> > > + 1, input_vtl, ®);
> > > + if (ret || !reg.value.reg64)
> > > + return -ENODEV;
> > > +
> > > + mshv_sint_vector = reg.value.reg64;
> > > + ret = mshv_acpi_setup_sint_irq();
> > > + if (ret <= 0) {
> > > + pr_err("Failed to setup IRQ for MSHV SINT vector %d: %d\n",
> > > + mshv_sint_vector, ret);
> > > + goto out_fail;
> > > + }
> > > +
> > > + mshv_sint_irq = ret;
> >
> > nit: given that mshv_sint_irq can't be zero, the logic can be simplified by
> > using 0 instead of -1.
>
> The test for <= 0 is actually wrong -- it should be just < 0. Zero is a valid
> Linux IRQ number. For example, here's the output of /proc/interrupts on
> a Gen1 VM on Hyper-V, where IRQ 0 is used by the legacy timer:
>
> root@gen1ubun:~# cat /proc/interrupts
> CPU0 CPU1 CPU2 CPU3
> 0: 18 0 0 0 IR-IO-APIC 2-edge
> timer
> 1: 0 9 0 0 IR-IO-APIC 1-edge
> i8042
> 4: 0 0 0 792 IR-IO-APIC 4-edge
> ttyS0
> 6: 6 0 0 0 IR-IO-APIC 6-edge
> floppy
> 8: 0 0 0 0 IR-IO-APIC 8-edge rtc0
> 9: 0 0 0 0 IR-IO-APIC 9-fasteoi acpi
>
> But I see other places throughout Linux kernel code that treat IRQ 0 as
> invalid. So I dunno .... But it's probably better to treat 0 as a valid IRQ
> number.
Agreed. I will fix this check in v6.
Thanks,
Anirudh.
>
> Michael
>
> >
> >
> >
> > > +
> > > + ret = request_percpu_irq(mshv_sint_irq, mshv_percpu_isr, "MSHV",
> > > + &mshv_evt);
> > > + if (ret)
> > > + goto out_unregister;
> > > +
> > > + return 0;
> > > +
> > > +out_unregister:
> > > + mshv_acpi_cleanup_sint_irq();
> > > +out_fail:
> > > + return ret;
> > > +}
> > > +
> > > +static void mshv_sint_vector_cleanup(void)
> > > +{
> > > + free_percpu_irq(mshv_sint_irq, &mshv_evt);
> > > + mshv_acpi_cleanup_sint_irq();
> > > +}
> > > +#else /* !HYPERVISOR_CALLBACK_VECTOR */
> > > +static int __init mshv_sint_vector_init(void)
> >
> > nit: `init` is usually paired with `exit` or `fini`, so maybe `cleanup` can
> > be
> > renamed to `exit` as well for better consistency?
> >
> > Reviewed-by: Stanislav Kinsburskii <[email protected]>
> >
> > > +{
> > > + mshv_sint_vector = HYPERVISOR_CALLBACK_VECTOR;
> > > + return 0;
> > > +}
> > > +
> > > +static void mshv_sint_vector_cleanup(void)
> > > +{
> > > +}
> > > +#endif /* HYPERVISOR_CALLBACK_VECTOR */
> > > +
> > > int __init mshv_synic_init(struct device *dev)
> > > {
> > > int ret = 0;
> > >
> > > + ret = mshv_sint_vector_init();
> > > + if (ret)
> > > + return ret;
> > > +
> > > synic_pages = alloc_percpu(struct hv_synic_pages);
> > > if (!synic_pages) {
> > > dev_err(dev, "Failed to allocate percpu synic page\n");
> > > - return -ENOMEM;
> > > + ret = -ENOMEM;
> > > + goto sint_vector_cleanup;
> > > }
> > >
> > > ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "mshv_synic",
> > > @@ -713,6 +810,8 @@ int __init mshv_synic_init(struct device *dev)
> > > cpuhp_remove_state(synic_cpuhp_online);
> > > free_synic_pages:
> > > free_percpu(synic_pages);
> > > +sint_vector_cleanup:
> > > + mshv_sint_vector_cleanup();
> > > return ret;
> > > }
> > >
> > > @@ -721,4 +820,5 @@ void mshv_synic_cleanup(void)
> > > unregister_reboot_notifier(&mshv_synic_reboot_nb);
> > > cpuhp_remove_state(synic_cpuhp_online);
> > > free_percpu(synic_pages);
> > > + mshv_sint_vector_cleanup();
> > > }
> > > diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
> > > index 30fbbde81c5c..7676f78e0766 100644
> > > --- a/include/hyperv/hvgdk_mini.h
> > > +++ b/include/hyperv/hvgdk_mini.h
> > > @@ -1117,6 +1117,8 @@ enum hv_register_name {
> > > HV_X64_REGISTER_MSR_MTRR_FIX4KF8000 = 0x0008007A,
> > >
> > > HV_X64_REGISTER_REG_PAGE = 0x0009001C,
> > > +#elif defined(CONFIG_ARM64)
> > > + HV_ARM64_REGISTER_SINT_RESERVED_INTERRUPT_ID = 0x00070001,
> > > #endif
> > > };
> > >
> > > --
> > > 2.34.1
> > >
>
