From: Vitaly Kuznetsov <[email protected]> Sent: Friday, January 2, 2026 7:55
AM
>
> Mukesh Rathor <[email protected]> writes:
>
> > MSVC compiler used to compile the Microsoft Hyper-V hypervisor currently,
> > has an assert intrinsic that uses interrupt vector 0x29 to create an
> > exception. This will cause hypervisor to then crash and collect core. As
> > such, if this interrupt number is assigned to a device by linux and the
> > device generates it, hypervisor will crash. There are two other such
> > vectors hard coded in the hypervisor, 0x2C and 0x2D.
> >
> > Fortunately, the three vectors are part of the kernel driver space, and
> > that makes it feasible to reserve them early so they are not assigned
> > later.
> >
> > Signed-off-by: Mukesh Rathor <[email protected]>
> > ---
> > arch/x86/kernel/cpu/mshyperv.c | 22 ++++++++++++++++++++++
> > 1 file changed, 22 insertions(+)
> >
> > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> > index 579fb2c64cfd..19d41f7434df 100644
> > --- a/arch/x86/kernel/cpu/mshyperv.c
> > +++ b/arch/x86/kernel/cpu/mshyperv.c
> > @@ -478,6 +478,25 @@ int hv_get_hypervisor_version(union
> > hv_hypervisor_version_info *info)
> > }
> > EXPORT_SYMBOL_GPL(hv_get_hypervisor_version);
> >
> > +/*
> > + * Reserve vectors hard coded in the hypervisor. If used outside, the
> > hypervisor
> > + * will crash or hang or break into debugger.
> > + */
> > +static void hv_reserve_irq_vectors(void)
> > +{
> > + #define HYPERV_DBG_FASTFAIL_VECTOR 0x29
> > + #define HYPERV_DBG_ASSERT_VECTOR 0x2C
> > + #define HYPERV_DBG_SERVICE_VECTOR 0x2D
> > +
> > + if (test_and_set_bit(HYPERV_DBG_ASSERT_VECTOR, system_vectors) ||
> > + test_and_set_bit(HYPERV_DBG_SERVICE_VECTOR, system_vectors) ||
> > + test_and_set_bit(HYPERV_DBG_FASTFAIL_VECTOR, system_vectors))
> > + BUG();
>
> Would it be less hackish to use sysvec_install() with a dummy handler
> for all three vectors instead?
It would be, but unfortunately, it doesn't work. sysvec_install() requires
that the vector be >= FIRST_SYSTEM_VECTOR, and these vectors are not.
Michael
>
> > +
> > + pr_info("Hyper-V:reserve vectors: %d %d %d\n", HYPERV_DBG_ASSERT_VECTOR,
> > + HYPERV_DBG_SERVICE_VECTOR, HYPERV_DBG_FASTFAIL_VECTOR);
> > +}
> > +
> > static void __init ms_hyperv_init_platform(void)
> > {
> > int hv_max_functions_eax, eax;
> > @@ -510,6 +529,9 @@ static void __init ms_hyperv_init_platform(void)
> >
> > hv_identify_partition_type();
> >
> > + if (hv_root_partition())
> > + hv_reserve_irq_vectors();
> > +
> > if (cc_platform_has(CC_ATTR_SNP_SECURE_AVIC))
> > ms_hyperv.hints |= HV_DEPRECATING_AEOI_RECOMMENDED;
>
> --
> Vitaly
>
