Re: x2apic boot failure on recent sandy bridge system

From: Yinghai Lu
Date: Sun Dec 11 2011 - 16:44:14 EST

On Sat, Dec 10, 2011 at 11:57 PM, Ingo Molnar <mingo@xxxxxxx> wrote:
>
> What we want is not a nox2apic option but a good fall-back
> mechanism that is able to boot the system automatically and
> safely, without the user having to tweak *anything* ...

Sure.

Attached -v4 should automatically switch to xapic mode.

Berck,
Can you please try -v4 patch on your setup when BIOS have x2apic enabled?

Thanks

Yinghai Lu
Subject: [PATCH -v4] x86: Disable x2apic if nox2apic is specified or intr-remap can not be enabled

For
1. x2apic preenabled system
2. first kernel have x2apic enabled, and try to kexec second kernel with "nox2apic"

Will put back cpu with apic id < 255 into xapic mode, instead of panic.

-v2: use x2apic_disabled instead of nox2apic, Suggested by Thomas
update x2apic_supported with x2apic_disabled, Suggested by Thomas

-v3: add checking for boot cpu apic id > 255. in that case will just panic
--- pointed out by Suresh.

-v4: according to Ingo, for x2apic pre-enabled system, if intr-remap can not
be enabled, try to disable x2apic instead of panic and request to
specify nox2apic for next boot.

Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>

---
arch/x86/include/asm/apic.h | 6 +-
arch/x86/include/asm/apicdef.h | 1
arch/x86/include/asm/processor.h | 1
arch/x86/kernel/acpi/boot.c | 10 +++-
arch/x86/kernel/apic/apic.c | 74 ++++++++++++++++++++++++++----------
arch/x86/kernel/apic/apic_flat_64.c | 7 ++-
arch/x86/kernel/cpu/topology.c | 21 ++++++++++
arch/x86/mm/srat.c | 7 ++-
8 files changed, 101 insertions(+), 26 deletions(-)

Index: linux-2.6/arch/x86/include/asm/apic.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/apic.h
+++ linux-2.6/arch/x86/include/asm/apic.h
@@ -176,6 +176,7 @@ static inline u64 native_x2apic_icr_read
}

extern int x2apic_phys;
+extern int x2apic_disabled;
extern void check_x2apic(void);
extern void enable_x2apic(void);
extern void x2apic_icr_write(u32 low, u32 id);
@@ -183,7 +184,7 @@ static inline int x2apic_enabled(void)
{
u64 msr;

- if (!cpu_has_x2apic)
+ if (!cpu_has_x2apic || x2apic_disabled)
return 0;

rdmsrl(MSR_IA32_APICBASE, msr);
@@ -192,7 +193,7 @@ static inline int x2apic_enabled(void)
return 0;
}

-#define x2apic_supported() (cpu_has_x2apic)
+#define x2apic_supported() (cpu_has_x2apic && !x2apic_disabled)
static inline void x2apic_force_phys(void)
{
x2apic_phys = 1;
@@ -214,6 +215,7 @@ static inline void x2apic_force_phys(voi

#define x2apic_preenabled 0
#define x2apic_supported() 0
+#define x2apic_disabled 1
#endif

extern void enable_IR_x2apic(void);
Index: linux-2.6/arch/x86/kernel/acpi/boot.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/acpi/boot.c
+++ linux-2.6/arch/x86/kernel/acpi/boot.c
@@ -219,6 +219,8 @@ static int __init
acpi_parse_x2apic(struct acpi_subtable_header *header, const unsigned long end)
{
struct acpi_madt_local_x2apic *processor = NULL;
+ int apic_id;
+ u8 enabled;

processor = (struct acpi_madt_local_x2apic *)header;

@@ -227,6 +229,8 @@ acpi_parse_x2apic(struct acpi_subtable_h

acpi_table_print_madt_entry(header);

+ apic_id = processor->local_apic_id;
+ enabled = processor->lapic_flags & ACPI_MADT_ENABLED;
#ifdef CONFIG_X86_X2APIC
/*
* We need to register disabled CPU as well to permit
@@ -235,8 +239,10 @@ acpi_parse_x2apic(struct acpi_subtable_h
* to not preallocating memory for all NR_CPUS
* when we use CPU hotplug.
*/
- acpi_register_lapic(processor->local_apic_id, /* APIC ID */
- processor->lapic_flags & ACPI_MADT_ENABLED);
+ if (x2apic_disabled && (apic_id >= 0xff) && enabled)
+ printk(KERN_WARNING PREFIX "x2apic entry ignored\n");
+ else
+ acpi_register_lapic(apic_id, enabled);
#else
printk(KERN_WARNING PREFIX "x2apic entry ignored\n");
#endif
Index: linux-2.6/arch/x86/kernel/apic/apic.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/apic.c
+++ linux-2.6/arch/x86/kernel/apic/apic.c
@@ -147,15 +147,14 @@ int x2apic_mode;
#ifdef CONFIG_X86_X2APIC
/* x2apic enabled before OS handover */
static int x2apic_preenabled;
+int x2apic_disabled;
static __init int setup_nox2apic(char *str)
{
- if (x2apic_enabled()) {
- pr_warning("Bios already enabled x2apic, "
- "can't enforce nox2apic");
- return 0;
- }
+ if (x2apic_enabled())
+ pr_warning("Bios already enabled x2apic, will disable it");
+
+ x2apic_disabled = 1;

- setup_clear_cpu_cap(X86_FEATURE_X2APIC);
return 0;
}
early_param("nox2apic", setup_nox2apic);
@@ -1431,8 +1430,38 @@ void __init bsp_end_local_APIC_setup(voi
}

#ifdef CONFIG_X86_X2APIC
+
+static void disable_x2apic(void)
+{
+ int msr, msr2;
+
+ if (!cpu_has_x2apic)
+ return;
+
+ rdmsr(MSR_IA32_APICBASE, msr, msr2);
+ if (msr & X2APIC_ENABLE) {
+ u32 x2apic_id = x2apic_cpuid_initial_apicid();
+
+ if (x2apic_id > 255)
+ panic("Can not disable x2apic, id: %08x\n", x2apic_id);
+
+ pr_info("Disabling x2apic\n");
+ /*
+ * Need to disable xapic and x2apic at the same time at first
+ * then enable xapic
+ */
+ wrmsr(MSR_IA32_APICBASE, msr & ~(X2APIC_ENABLE | XAPIC_ENABLE),
+ 0);
+ wrmsr(MSR_IA32_APICBASE, msr & ~X2APIC_ENABLE, 0);
+ }
+}
void check_x2apic(void)
{
+ if (x2apic_disabled) {
+ disable_x2apic();
+ return;
+ }
+
if (x2apic_enabled()) {
pr_info("x2apic enabled by BIOS, switching to x2apic ops\n");
x2apic_preenabled = x2apic_mode = 1;
@@ -1443,6 +1472,11 @@ void enable_x2apic(void)
{
int msr, msr2;

+ if (x2apic_disabled) {
+ disable_x2apic();
+ return;
+ }
+
if (!x2apic_mode)
return;

@@ -1493,7 +1527,7 @@ void __init enable_IR_x2apic(void)
ret = save_ioapic_entries();
if (ret) {
pr_info("Saving IO-APIC state failed: %d\n", ret);
- goto out;
+ return;
}

local_irq_save(flags);
@@ -1505,13 +1539,22 @@ void __init enable_IR_x2apic(void)
else
ret = enable_IR();

+ if (x2apic_disabled)
+ goto nox2apic;
+
if (ret < 0) {
/* IR is required if there is APIC ID > 255 even when running
* under KVM
*/
if (max_physical_apicid > 255 ||
- !hypervisor_x2apic_available())
+ !hypervisor_x2apic_available()) {
+ if (x2apic_preenabled) {
+ disable_x2apic();
+ x2apic_disabled = 1;
+ x2apic_mode = 0;
+ }
goto nox2apic;
+ }
/*
* without IR all CPUs can be addressed by IOAPIC/MSI
* only in physical mode
@@ -1519,8 +1562,10 @@ void __init enable_IR_x2apic(void)
x2apic_force_phys();
}

- if (ret == IRQ_REMAP_XAPIC_MODE)
+ if (ret == IRQ_REMAP_XAPIC_MODE) {
+ pr_info("x2apic not enabled, IRQ remapping is in xapic mode\n");
goto nox2apic;
+ }

x2apic_enabled = 1;

@@ -1535,17 +1580,6 @@ nox2apic:
restore_ioapic_entries();
legacy_pic->restore_mask();
local_irq_restore(flags);
-
-out:
- if (x2apic_enabled || !x2apic_supported())
- return;
-
- if (x2apic_preenabled)
- panic("x2apic: enabled by BIOS but kernel init failed.");
- else if (ret == IRQ_REMAP_XAPIC_MODE)
- pr_info("x2apic not enabled, IRQ remapping is in xapic mode\n");
- else if (ret < 0)
- pr_info("x2apic not enabled, IRQ remapping init failed\n");
}

#ifdef CONFIG_X86_64
Index: linux-2.6/arch/x86/mm/srat.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/srat.c
+++ linux-2.6/arch/x86/mm/srat.c
@@ -69,6 +69,12 @@ acpi_numa_x2apic_affinity_init(struct ac
if ((pa->flags & ACPI_SRAT_CPU_ENABLED) == 0)
return;
pxm = pa->proximity_domain;
+ apic_id = pa->apic_id;
+ if (x2apic_disabled && (apic_id >= 0xff)) {
+ printk(KERN_INFO "SRAT: PXM %u -> X2APIC 0x%04x ignored\n",
+ pxm, apic_id);
+ return;
+ }
node = setup_node(pxm);
if (node < 0) {
printk(KERN_ERR "SRAT: Too many proximity domains %x\n", pxm);
@@ -76,7 +82,6 @@ acpi_numa_x2apic_affinity_init(struct ac
return;
}

- apic_id = pa->apic_id;
if (apic_id >= MAX_LOCAL_APIC) {
printk(KERN_INFO "SRAT: PXM %u -> APIC 0x%04x -> Node %u skipped apicid that is too big\n", pxm, apic_id, node);
return;
Index: linux-2.6/arch/x86/include/asm/apicdef.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/apicdef.h
+++ linux-2.6/arch/x86/include/asm/apicdef.h
@@ -144,6 +144,7 @@

#define APIC_BASE (fix_to_virt(FIX_APIC_BASE))
#define APIC_BASE_MSR 0x800
+#define XAPIC_ENABLE (1UL << 11)
#define X2APIC_ENABLE (1UL << 10)

#ifdef CONFIG_X86_32
Index: linux-2.6/arch/x86/include/asm/processor.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/processor.h
+++ linux-2.6/arch/x86/include/asm/processor.h
@@ -168,6 +168,7 @@ extern void init_scattered_cpuid_feature
extern unsigned int init_intel_cacheinfo(struct cpuinfo_x86 *c);
extern unsigned short num_cache_leaves;

+u32 x2apic_cpuid_initial_apicid(void);
extern void detect_extended_topology(struct cpuinfo_x86 *c);
extern void detect_ht(struct cpuinfo_x86 *c);

Index: linux-2.6/arch/x86/kernel/cpu/topology.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/topology.c
+++ linux-2.6/arch/x86/kernel/cpu/topology.c
@@ -21,6 +21,27 @@
#define BITS_SHIFT_NEXT_LEVEL(eax) ((eax) & 0x1f)
#define LEVEL_MAX_SIBLINGS(ebx) ((ebx) & 0xffff)

+u32 x2apic_cpuid_initial_apicid(void)
+{
+ unsigned int eax, ebx, ecx, edx;
+
+ if (boot_cpu_data.cpuid_level < 0xb)
+ return 0;
+
+ cpuid_count(0xb, SMT_LEVEL, &eax, &ebx, &ecx, &edx);
+
+ /*
+ * check if the cpuid leaf 0xb is actually implemented.
+ */
+ if (ebx == 0 || (LEAFB_SUBTYPE(ecx) != SMT_TYPE))
+ return 0;
+
+ /*
+ * initial apic id, which also represents 32-bit extended x2apic id.
+ */
+ return edx;
+}
+
/*
* Check for extended topology enumeration cpuid leaf 0xb and if it
* exists, use it for populating initial_apicid and cpu topology
Index: linux-2.6/arch/x86/kernel/apic/apic_flat_64.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/apic_flat_64.c
+++ linux-2.6/arch/x86/kernel/apic/apic_flat_64.c
@@ -171,9 +171,14 @@ static int flat_phys_pkg_id(int initial_
return initial_apic_id >> index_msb;
}

+static int flat_probe(void)
+{
+ return 1;
+}
+
static struct apic apic_flat = {
.name = "flat",
- .probe = NULL,
+ .probe = flat_probe,
.acpi_madt_oem_check = flat_acpi_madt_oem_check,
.apic_id_registered = flat_apic_id_registered,