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Message-Id: <20230824080712.30327-5-decui@microsoft.com>
Date: Thu, 24 Aug 2023 01:07:06 -0700
From: Dexuan Cui <decui@...rosoft.com>
To: ak@...ux.intel.com, arnd@...db.de, bp@...en8.de,
brijesh.singh@....com, dan.j.williams@...el.com,
dave.hansen@...el.com, dave.hansen@...ux.intel.com,
haiyangz@...rosoft.com, hpa@...or.com, jane.chu@...cle.com,
kirill.shutemov@...ux.intel.com, kys@...rosoft.com,
linux-hyperv@...r.kernel.org, luto@...nel.org, mingo@...hat.com,
peterz@...radead.org, rostedt@...dmis.org,
sathyanarayanan.kuppuswamy@...ux.intel.com, seanjc@...gle.com,
tglx@...utronix.de, tony.luck@...el.com, wei.liu@...nel.org,
Jason@...c4.com, nik.borisov@...e.com, mikelley@...rosoft.com
Cc: x86@...nel.org, linux-kernel@...r.kernel.org,
linux-arch@...r.kernel.org, Tianyu.Lan@...rosoft.com,
rick.p.edgecombe@...el.com, andavis@...hat.com, mheslin@...hat.com,
vkuznets@...hat.com, xiaoyao.li@...el.com,
Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH v3 04/10] 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 <mikelley@...rosoft.com>
Reviewed-by: Tianyu Lan <tiala@...rosoft.com>
Signed-off-by: Dexuan Cui <decui@...rosoft.com>
---
Changes in v2: None
Changes in v3:
Added Tianyu's Reviewed-by.
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 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;
}
}
}
--
2.25.1
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