From 0719881bf891cc72bf4375a9f4849d52772c80c6 Mon Sep 17 00:00:00 2001 From: Dexuan Cui Date: Thu, 24 Aug 2023 01:07:06 -0700 Subject: x86/hyperv: Fix serial console interrupts for fully enlightened TDX guests 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 Reviewed-by: Tianyu Lan Signed-off-by: Dexuan Cui Signed-off-by: Wei Liu Link: https://lore.kernel.org/r/20230824080712.30327-5-decui@microsoft.com --- arch/x86/kernel/cpu/mshyperv.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'arch/x86/kernel/cpu/mshyperv.c') diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index ff3d9c5de19c..fe5393d759d3 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -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; } } } -- cgit