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x86/hyperv: Fix serial console interrupts for fully enlightened TDX guests

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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>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Link: https://lore.kernel.org/r/20230824080712.30327-5-decui@microsoft.com
This commit is contained in:
Dexuan Cui 2023-08-24 01:07:06 -07:00 • committed by Wei Liu
parent 68f2f2bc16
commit 0719881bf8
1 changed files with 22 additions and 0 deletions
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22
arch/x86/kernel/cpu/mshyperv.c
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@ -323,6 +323,26 @@ 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;
@ -433,6 +453,8 @@ 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;
}
}
}