From: Thomas Gleixner tglx@linutronix.de
mainline inclusion from mainline-v5.6-rc1 commit 979923871f69 category: bugfix bugzilla: 17251 CVE: NA
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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
Signed-off-by: Xiongfeng Wang wangxiongfeng2@huawei.com Reviewed-by: Hanjun Guo guohanjun@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- arch/x86/include/asm/apic.h | 2 ++ arch/x86/include/asm/x86_init.h | 2 ++ arch/x86/kernel/apic/apic.c | 23 ++++++++++++++++++----- arch/x86/kernel/time.c | 12 ++++++++++-- arch/x86/kernel/x86_init.c | 1 + arch/x86/xen/enlighten_pv.c | 1 + 6 files changed, 34 insertions(+), 7 deletions(-)
diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h index b18fdea..b7bd996 100644 --- a/arch/x86/include/asm/apic.h +++ b/arch/x86/include/asm/apic.h @@ -138,6 +138,7 @@ static inline bool apic_is_x2apic_enabled(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); @@ -185,6 +186,7 @@ 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 b85a7c5..227b18b 100644 --- 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 7bdc5ce..8fe688e 100644 --- a/arch/x86/kernel/apic/apic.c +++ b/arch/x86/kernel/apic/apic.c @@ -823,8 +823,17 @@ 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;
/* Deadline timer is based on TSC so no further PIT action required */ @@ -1298,7 +1307,7 @@ void __init sync_Arb_IDs(void)
enum apic_intr_mode_id apic_intr_mode;
-static int __init apic_intr_mode_select(void) +static int __init __apic_intr_mode_select(void) { /* Check kernel option */ if (disable_apic) { @@ -1360,6 +1369,12 @@ 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. */ @@ -1414,8 +1429,6 @@ 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 548dc9a..8a2ac1c 100644 --- 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 2792b55..915a305 100644 --- a/arch/x86/kernel/x86_init.c +++ b/arch/x86/kernel/x86_init.c @@ -59,6 +59,7 @@ 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 1730a26..3efafe2 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -1219,6 +1219,7 @@ 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;