On Mon, Feb 23, 2026 at 05:53:03PM +0000, Michael Kelley wrote:
> From: Anirudh Rayabharam <[email protected]> Sent: Monday, February 23,
> 2026 6:02 AM
> >
> > On x86, the HYPERVISOR_CALLBACK_VECTOR is used to receive synthetic
> > interrupts (SINTs) from the hypervisor for doorbells and intercepts.
> > There is no such vector reserved for arm64.
> >
> > On arm64, the hypervisor exposes a synthetic register that can be read
> > to find the INTID that should be used for SINTs. This INTID is in the
> > PPI range.
> >
> > To better unify the code paths, introduce mshv_sint_vector_init() that
> > either reads the synthetic register and obtains the INTID (arm64) or
> > just uses HYPERVISOR_CALLBACK_VECTOR as the interrupt vector (x86).
> >
> > Signed-off-by: Anirudh Rayabharam (Microsoft) <[email protected]>
> > ---
> > drivers/hv/mshv_synic.c | 120 +++++++++++++++++++++++++++++++++---
> > include/hyperv/hvgdk_mini.h | 2 +
> > 2 files changed, 112 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/hv/mshv_synic.c b/drivers/hv/mshv_synic.c
> > index 074e37c48876..75ef2160b3e0 100644
> > --- a/drivers/hv/mshv_synic.c
> > +++ b/drivers/hv/mshv_synic.c
> > @@ -10,17 +10,22 @@
> > #include <linux/kernel.h>
> > #include <linux/slab.h>
> > #include <linux/mm.h>
> > +#include <linux/interrupt.h>
> > #include <linux/io.h>
> > #include <linux/random.h>
> > #include <linux/cpuhotplug.h>
> > #include <linux/reboot.h>
> > #include <asm/mshyperv.h>
> > +#include <linux/platform_device.h>
>
> I don't think this #include is needed now that you've switched to getting
> the INTID via a hypercall instead of via an ACPI device.
>
> The rest of the changes look good to me. You have a place carved out
> to put the DT setup of the mshv_sint_irq, and the scope of all the
> variables and mshv_percpu_isr() is correct so that there won't be any
> "unused" warnings generated. Nice!
>
> Modulo the unnecessary #include,
> Reviewed-by: Michael Kelley <[email protected]>
Thanks! I'll get rid of the unnecessary include in v6 and also pick-up
your Reviewed-by.
Anirudh.
>
> > +#include <linux/acpi.h>
> >
> > #include "mshv_eventfd.h"
> > #include "mshv.h"
> >
> > static int synic_cpuhp_online;
> > static struct hv_synic_pages __percpu *synic_pages;
> > +static int mshv_sint_vector = -1; /* hwirq for the SynIC SINTs */
> > +static int mshv_sint_irq = -1; /* Linux IRQ for mshv_sint_vector */
> >
> > static u32 synic_event_ring_get_queued_port(u32 sint_index)
> > {
> > @@ -442,9 +447,7 @@ void mshv_isr(void)
> > if (msg->header.message_flags.msg_pending)
> > hv_set_non_nested_msr(HV_MSR_EOM, 0);
> >
> > -#ifdef HYPERVISOR_CALLBACK_VECTOR
> > - add_interrupt_randomness(HYPERVISOR_CALLBACK_VECTOR);
> > -#endif
> > + add_interrupt_randomness(mshv_sint_vector);
> > } else {
> > pr_warn_once("%s: unknown message type 0x%x\n", __func__,
> > msg->header.message_type);
> > @@ -456,9 +459,7 @@ static int mshv_synic_cpu_init(unsigned int cpu)
> > union hv_synic_simp simp;
> > union hv_synic_siefp siefp;
> > union hv_synic_sirbp sirbp;
> > -#ifdef HYPERVISOR_CALLBACK_VECTOR
> > union hv_synic_sint sint;
> > -#endif
> > union hv_synic_scontrol sctrl;
> > struct hv_synic_pages *spages = this_cpu_ptr(synic_pages);
> > struct hv_message_page **msg_page = &spages->hyp_synic_message_page;
> > @@ -501,10 +502,12 @@ static int mshv_synic_cpu_init(unsigned int cpu)
> >
> > hv_set_non_nested_msr(HV_MSR_SIRBP, sirbp.as_uint64);
> >
> > -#ifdef HYPERVISOR_CALLBACK_VECTOR
> > + if (mshv_sint_irq != -1)
> > + enable_percpu_irq(mshv_sint_irq, 0);
> > +
> > /* Enable intercepts */
> > sint.as_uint64 = 0;
> > - sint.vector = HYPERVISOR_CALLBACK_VECTOR;
> > + sint.vector = mshv_sint_vector;
> > sint.masked = false;
> > sint.auto_eoi = hv_recommend_using_aeoi();
> > hv_set_non_nested_msr(HV_MSR_SINT0 +
> > HV_SYNIC_INTERCEPTION_SINT_INDEX,
> > @@ -512,13 +515,12 @@ static int mshv_synic_cpu_init(unsigned int cpu)
> >
> > /* Doorbell SINT */
> > sint.as_uint64 = 0;
> > - sint.vector = HYPERVISOR_CALLBACK_VECTOR;
> > + sint.vector = mshv_sint_vector;
> > sint.masked = false;
> > sint.as_intercept = 1;
> > sint.auto_eoi = hv_recommend_using_aeoi();
> > hv_set_non_nested_msr(HV_MSR_SINT0 + HV_SYNIC_DOORBELL_SINT_INDEX,
> > sint.as_uint64);
> > -#endif
> >
> > /* Enable global synic bit */
> > sctrl.as_uint64 = hv_get_non_nested_msr(HV_MSR_SCONTROL);
> > @@ -573,6 +575,9 @@ static int mshv_synic_cpu_exit(unsigned int cpu)
> > hv_set_non_nested_msr(HV_MSR_SINT0 + HV_SYNIC_DOORBELL_SINT_INDEX,
> > sint.as_uint64);
> >
> > + if (mshv_sint_irq != -1)
> > + disable_percpu_irq(mshv_sint_irq);
> > +
> > /* Disable Synic's event ring page */
> > sirbp.as_uint64 = hv_get_non_nested_msr(HV_MSR_SIRBP);
> > sirbp.sirbp_enabled = false;
> > @@ -683,14 +688,106 @@ static struct notifier_block mshv_synic_reboot_nb = {
> > .notifier_call = mshv_synic_reboot_notify,
> > };
> >
> > +#ifndef HYPERVISOR_CALLBACK_VECTOR
> > +static DEFINE_PER_CPU(long, mshv_evt);
> > +
> > +static irqreturn_t mshv_percpu_isr(int irq, void *dev_id)
> > +{
> > + mshv_isr();
> > + return IRQ_HANDLED;
> > +}
> > +
> > +#ifdef CONFIG_ACPI
> > +static int __init mshv_acpi_setup_sint_irq(void)
> > +{
> > + return acpi_register_gsi(NULL, mshv_sint_vector, ACPI_EDGE_SENSITIVE,
> > + ACPI_ACTIVE_HIGH);
> > +}
> > +
> > +static void mshv_acpi_cleanup_sint_irq(void)
> > +{
> > + acpi_unregister_gsi(mshv_sint_vector);
> > +}
> > +#else
> > +static int __init mshv_acpi_setup_sint_irq(void)
> > +{
> > + return -ENODEV;
> > +}
> > +
> > +static void mshv_acpi_cleanup_sint_irq(void)
> > +{
> > +}
> > +#endif
> > +
> > +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;
> > +
> > + 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)
> > +{
> > + 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
> >
>
