[PATCH 1/1][SRU][B/OEM-B] x86/timer: Don't skip PIT setup when APIC is disabled or in legacy mode
You-Sheng Yang
vicamo.yang at canonical.com
Fri Jun 12 11:52:00 UTC 2020
From: Thomas Gleixner <tglx at linutronix.de>
BugLink: https://bugs.launchpad.net/bugs/1856387
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 at gmail.com>
Tested-by: Anthony Buckley <tony.buckley000 at gmail.com>
Signed-off-by: Thomas Gleixner <tglx at linutronix.de>
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Cc: Daniel Drake <drake at endlessm.com>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206125
Link: https://lore.kernel.org/r/87sgk6tmk2.fsf@nanos.tec.linutronix.de
(backported from commit 979923871f69a4dc926658f9f9a1a4c1bde57552)
Signed-off-by: You-Sheng Yang <vicamo.yang at canonical.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 3df5d195d647..314a5b54a485 100644
--- a/arch/x86/include/asm/apic.h
+++ b/arch/x86/include/asm/apic.h
@@ -138,6 +138,7 @@ extern void disable_local_APIC(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 setup_local_APIC(void);
extern void init_apic_mappings(void);
@@ -185,6 +186,7 @@ static inline void disable_local_APIC(void) { }
# define setup_boot_APIC_clock x86_init_noop
# define setup_secondary_APIC_clock x86_init_noop
static inline void lapic_update_tsc_freq(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 aa4747569e23..2803cef02c14 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 f15084536abe..d0cd6722c180 100644
--- a/arch/x86/kernel/apic/apic.c
+++ b/arch/x86/kernel/apic/apic.c
@@ -805,8 +805,17 @@ 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 */
@@ -1293,7 +1302,7 @@ 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) {
@@ -1355,6 +1364,12 @@ 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.
*/
@@ -1409,8 +1424,6 @@ 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 5339ffd488d0..fd6deda443f9 100644
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -88,10 +88,18 @@ 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 1151ccd72ce9..6c9adc14df26 100644
--- a/arch/x86/kernel/x86_init.c
+++ b/arch/x86/kernel/x86_init.c
@@ -57,6 +57,7 @@ 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 88c6d9d7e284..c2556f32f156 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1246,6 +1246,7 @@ 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;
--
2.27.0.rc0
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