x86/timer: Don't skip PIT setup when APIC is disabled or in legacy mode

Tony reported a boot regression caused by the recent workaround for systems
which have a disabled (clock gate off) PIT.

On his machine the kernel fails to initialize the PIT because
apic_needs_pit() does not take into account whether the local APIC
interrupt delivery mode will actually allow to setup and use the local
APIC timer. This should be easy to reproduce with acpi=off on the
command line which also disables HPET.

Due to the way the PIT/HPET and APIC setup ordering works (APIC setup can
require working PIT/HPET) the information is not available at the point
where apic_needs_pit() makes this decision.

To address this, split out the interrupt mode selection from
apic_intr_mode_init(), invoke the selection before making the decision
whether PIT is required or not, and add the missing checks into
apic_needs_pit().

Fixes: c8c4076723da ("x86/timer: Skip PIT initialization on modern chipsets")
Reported-by: Anthony Buckley <tony.buckley000@gmail.com>
Tested-by: Anthony Buckley <tony.buckley000@gmail.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Daniel Drake <drake@endlessm.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206125
Link: https://lore.kernel.org/r/87sgk6tmk2.fsf@nanos.tec.linutronix.de

diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h
index 2ebc17d9c72cddb06827afa038243dd56e1a3cd7..be0b9cf941c4e3d539bc511ddffe487b3414a684 100644 (file)
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -140,6 +140,7 @@ extern void apic_soft_disable(void);
 extern void lapic_shutdown(void);
 extern void sync_Arb_IDs(void);
 extern void init_bsp_APIC(void);
+extern void apic_intr_mode_select(void);
 extern void apic_intr_mode_init(void);
 extern void init_apic_mappings(void);
 void register_lapic_address(unsigned long address);
@@ -188,6 +189,7 @@ static inline void disable_local_APIC(void) { }
 # define setup_secondary_APIC_clock x86_init_noop
 static inline void lapic_update_tsc_freq(void) { }
 static inline void init_bsp_APIC(void) { }
+static inline void apic_intr_mode_select(void) { }
 static inline void apic_intr_mode_init(void) { }
 static inline void lapic_assign_system_vectors(void) { }
 static inline void lapic_assign_legacy_vector(unsigned int i, bool r) { }

diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 19435858df5f147ad950cf03fe2811a09d20ab73..96d9cd2086104c9cccddedec7a7bf1bc108d32be 100644 (file)
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -51,12 +51,14 @@ struct x86_init_resources {
  *                             are set up.
  * @intr_init:                 interrupt init code
  * @trap_init:                 platform specific trap setup
+ * @intr_mode_select:          interrupt delivery mode selection
  * @intr_mode_init:            interrupt delivery mode setup
  */
 struct x86_init_irqs {
        void (*pre_vector_init)(void);
        void (*intr_init)(void);
        void (*trap_init)(void);
+       void (*intr_mode_select)(void);
        void (*intr_mode_init)(void);
 };
 

diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c
index 28446fa6bf1851d54da7f6ab9fa79648966712e8..4b0f9117e1cd8ce68f1f7514e5f8584f327f23a2 100644 (file)
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -830,8 +830,17 @@ bool __init apic_needs_pit(void)
        if (!tsc_khz || !cpu_khz)
                return true;
 
-       /* Is there an APIC at all? */
-       if (!boot_cpu_has(X86_FEATURE_APIC))
+       /* Is there an APIC at all or is it disabled? */
+       if (!boot_cpu_has(X86_FEATURE_APIC) || disable_apic)
+               return true;
+
+       /*
+        * If interrupt delivery mode is legacy PIC or virtual wire without
+        * configuration, the local APIC timer wont be set up. Make sure
+        * that the PIT is initialized.
+        */
+       if (apic_intr_mode == APIC_PIC ||
+           apic_intr_mode == APIC_VIRTUAL_WIRE_NO_CONFIG)
                return true;
 
        /* Virt guests may lack ARAT, but still have DEADLINE */
@@ -1322,7 +1331,7 @@ void __init sync_Arb_IDs(void)
 
 enum apic_intr_mode_id apic_intr_mode __ro_after_init;
 
-static int __init apic_intr_mode_select(void)
+static int __init __apic_intr_mode_select(void)
 {
        /* Check kernel option */
        if (disable_apic) {
@@ -1384,6 +1393,12 @@ static int __init apic_intr_mode_select(void)
        return APIC_SYMMETRIC_IO;
 }
 
+/* Select the interrupt delivery mode for the BSP */
+void __init apic_intr_mode_select(void)
+{
+       apic_intr_mode = __apic_intr_mode_select();
+}
+
 /*
  * An initial setup of the virtual wire mode.
  */
@@ -1440,8 +1455,6 @@ void __init apic_intr_mode_init(void)
 {
        bool upmode = IS_ENABLED(CONFIG_UP_LATE_INIT);
 
-       apic_intr_mode = apic_intr_mode_select();
-
        switch (apic_intr_mode) {
        case APIC_PIC:
                pr_info("APIC: Keep in PIC mode(8259)\n");

diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
index 7ce29cee9f9e624d7589b88834f764e5576a87e3..d8673d8a779b5c22d107dd8fa70fb818aaf4e58a 100644 (file)
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -91,10 +91,18 @@ void __init hpet_time_init(void)
 
 static __init void x86_late_time_init(void)
 {
+       /*
+        * Before PIT/HPET init, select the interrupt mode. This is required
+        * to make the decision whether PIT should be initialized correct.
+        */
+       x86_init.irqs.intr_mode_select();
+
+       /* Setup the legacy timers */
        x86_init.timers.timer_init();
+
        /*
-        * After PIT/HPET timers init, select and setup
-        * the final interrupt mode for delivering IRQs.
+        * After PIT/HPET timers init, set up the final interrupt mode for
+        * delivering IRQs.
         */
        x86_init.irqs.intr_mode_init();
        tsc_init();

diff --git a/arch/x86/kernel/x86_init.c b/arch/x86/kernel/x86_init.c
index ce89430a7f8011aa5d49e1ee99dcae19a9862cf1..9a89261dcd2a6b71f005a63fff8a67541c34d5d4 100644 (file)
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -80,6 +80,7 @@ struct x86_init_ops x86_init __initdata = {
                .pre_vector_init        = init_ISA_irqs,
                .intr_init              = native_init_IRQ,
                .trap_init              = x86_init_noop,
+               .intr_mode_select       = apic_intr_mode_select,
                .intr_mode_init         = apic_intr_mode_init
        },
 

diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index ae4a41ca19f6244eab9063c64d9688c7c350001d..1f756ffffe8b3159dade936c5eecda8d847900b8 100644 (file)
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1205,6 +1205,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
        x86_platform.get_nmi_reason = xen_get_nmi_reason;
 
        x86_init.resources.memory_setup = xen_memory_setup;
+       x86_init.irqs.intr_mode_select  = x86_init_noop;
        x86_init.irqs.intr_mode_init    = x86_init_noop;
        x86_init.oem.arch_setup = xen_arch_setup;
        x86_init.oem.banner = xen_banner;