Messages in this thread | | | Date | Wed, 23 Aug 2023 16:17:54 +0800 | Subject | Re: [PATCH 4/9] x86/hyperv: Fix serial console interrupts for fully enlightened TDX guests | From | Tianyu Lan <> |
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On 8/12/2023 6:18 AM, Dexuan Cui wrote: > When a fully enlightened TDX guest runs on Hyper-V, the UEFI firmware sets > the HW_REDUCED flag and consequently ttyS0 interrupts can't work. Fix the > issue by overriding x86_init.acpi.reduced_hw_early_init(). > > Reviewed-by: Michael Kelley <mikelley@microsoft.com> > Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Tianyu Lan <tiala@microsoft.com> > --- > 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 507df0f64ae18..b4214e37e9124 100644 > --- a/arch/x86/kernel/cpu/mshyperv.c > +++ b/arch/x86/kernel/cpu/mshyperv.c > @@ -324,6 +324,26 @@ static void __init hv_smp_prepare_cpus(unsigned int max_cpus) > } > #endif > > +/* > + * When a fully enlightened TDX VM runs on Hyper-V, the firmware sets the > + * HW_REDUCED flag: refer to acpi_tb_create_local_fadt(). Consequently ttyS0 > + * interrupts can't work because request_irq() -> ... -> irq_to_desc() returns > + * NULL for ttyS0. This happens because mp_config_acpi_legacy_irqs() sees a > + * nr_legacy_irqs() of 0, so it doesn't initialize the array 'mp_irqs[]', and > + * later setup_IO_APIC_irqs() -> find_irq_entry() fails to find the legacy irqs > + * from the array and hence doesn't create the necessary irq description info. > + * > + * Clone arch/x86/kernel/acpi/boot.c: acpi_generic_reduced_hw_init() here, > + * except don't change 'legacy_pic', which keeps its default value > + * 'default_legacy_pic'. This way, mp_config_acpi_legacy_irqs() sees a non-zero > + * nr_legacy_irqs() and eventually serial console interrupts works properly. > + */ > +static void __init reduced_hw_init(void) > +{ > + x86_init.timers.timer_init = x86_init_noop; > + x86_init.irqs.pre_vector_init = x86_init_noop; > +} > + > static void __init ms_hyperv_init_platform(void) > { > int hv_max_functions_eax; > @@ -442,6 +462,8 @@ static void __init ms_hyperv_init_platform(void) > > /* Don't trust Hyper-V's TLB-flushing hypercalls. */ > ms_hyperv.hints &= ~HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED; > + > + x86_init.acpi.reduced_hw_early_init = reduced_hw_init; > } > } > }
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