[PATCH -v3] x86: Disable x2apic if nox2apic is specified
From: Yinghai Lu
Date: Wed Oct 27 2010 - 02:30:05 EST
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.
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 | 51 +++++++++++++++++++++++++++++++++------
arch/x86/kernel/cpu/topology.c | 21 ++++++++++++++++
arch/x86/mm/srat_64.c | 7 ++++-
7 files changed, 85 insertions(+), 12 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)
{
int msr, msr2;
- if (!cpu_has_x2apic)
+ if (!cpu_has_x2apic || x2apic_disabled)
return 0;
rdmsr(MSR_IA32_APICBASE, msr, msr2);
@@ -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
@@ -213,6 +213,8 @@ 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;
@@ -221,6 +223,8 @@ 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
@@ -229,8 +233,10 @@ 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
@@ -138,15 +138,14 @@ 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);
@@ -1394,8 +1393,38 @@ void __cpuinit end_local_APIC_setup(void
}
#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;
@@ -1406,6 +1435,11 @@ void enable_x2apic(void)
{
int msr, msr2;
+ if (x2apic_disabled) {
+ disable_x2apic();
+ return;
+ }
+
if (!x2apic_mode)
return;
@@ -1474,6 +1508,9 @@ void __init enable_IR_x2apic(void)
else
ret = enable_IR();
+ if (x2apic_disabled)
+ goto nox2apic;
+
if (!ret) {
/* IR is required if there is APIC ID > 255 even when running
* under KVM
@@ -1510,7 +1547,7 @@ out:
if (x2apic_preenabled)
panic("x2apic: enabled by BIOS but kernel init failed.");
- else if (cpu_has_x2apic)
+ else if (cpu_has_x2apic && !x2apic_disabled)
pr_info("Not enabling x2apic, Intr-remapping init failed.\n");
}
Index: linux-2.6/arch/x86/mm/srat_64.c
===================================================================
--- linux-2.6.orig/arch/x86/mm/srat_64.c
+++ linux-2.6/arch/x86/mm/srat_64.c
@@ -126,6 +126,12 @@ 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);
@@ -133,7 +139,6 @@ acpi_numa_x2apic_affinity_init(struct ac
return;
}
- apic_id = pa->apic_id;
apicid_to_node[apic_id] = node;
node_set(node, cpu_nodes_parsed);
acpi_numa = 1;
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
@@ -141,6 +141,7 @@
#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
@@ -172,6 +172,7 @@ 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
--
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