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Subject[PATCH] x86, apic: Check fadt x2apic phys in x2apic_phys_probe()
Date
From: Stoney Wang <song-bo.wang@hp.com>

When HP ProLiant DL980 G7 Server boot without x2apic_phys, there will be
intermittent lost interrupts and could result in a hang or data loss.

Those systems only work with x2apic phys mode so BIOS set
ACPI_FADT_APIC_PHYSICAL in FADT table.
Also because all apicids are less then 255, BIOS need to pass the control
to the OS with xapic mode, according to x2apic-spec, chapter 2.9.

Current code handle x2apic when BIOS pass with xapic mode:

When user specify x2apic_phys, or FADT indicates PHYSICAL.
During madt oem check, apic driver is set with xapic logical or
xapic phys driver at first.
Later enable_IR_x2apic() will enable x2apic_mode.
After that, x2apic_phys_probe() will install right x2apic phys driver
if user specify x2apic_phys,
but will skip and let x2apic_cluster_probe to take over to install
wrong apic driver (x2apic cluster) when FADT indicates
PHYSICAL, because x2apic_phys_probe does not check FADT PHYSICAL.

Add checking x2apic_fadt_phys in x2apic_phys_probe() to fix the problem.

-v3: update the change according to Ingo.

[ changelog, and simplify code - Yinghai Lu ]
Signed-off-by: Stoney Wang <song-bo.wang@hp.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: stable@kernel.org

---
arch/x86/kernel/apic/x2apic_phys.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)

Index: linux-2.6/arch/x86/kernel/apic/x2apic_phys.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/apic/x2apic_phys.c
+++ linux-2.6/arch/x86/kernel/apic/x2apic_phys.c
@@ -20,18 +20,19 @@ static int set_x2apic_phys_mode(char *ar
}
early_param("x2apic_phys", set_x2apic_phys_mode);

-static int x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
+static bool x2apic_fadt_phys(void)
{
- if (x2apic_phys)
- return x2apic_enabled();
- else if ((acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID) &&
- (acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL) &&
- x2apic_enabled()) {
+ if ((acpi_gbl_FADT.header.revision >= FADT2_REVISION_ID) &&
+ (acpi_gbl_FADT.flags & ACPI_FADT_APIC_PHYSICAL)) {
printk(KERN_DEBUG "System requires x2apic physical mode\n");
- return 1;
+ return true;
}
- else
- return 0;
+ return false;
+}
+
+static int x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
+{
+ return x2apic_enabled() && (x2apic_phys || x2apic_fadt_phys());
}

static void
@@ -82,7 +83,7 @@ static void init_x2apic_ldr(void)

static int x2apic_phys_probe(void)
{
- if (x2apic_mode && x2apic_phys)
+ if (x2apic_mode && (x2apic_phys || x2apic_fadt_phys()))
return 1;

return apic == &apic_x2apic_phys;

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