[stable 3.0 v2] x86/apic: Work around boot failure on HP ProLiantDL980 G7 Server systems

[Zhang, Lin-Bao (Linux Kernel R&D)]

Hi Greg,

This patch is specially for 3.0 by integrating upstream commit cb214ede7657db458fd0b2a25ea0b28dbf900ebc 
and ea0dcf903e7d76aa5d483d876215fedcfdfe140f .
I fixed patch format warning and re-send it as v2. Thanks . 

-----------------------
./scripts/checkpatch.pl x2apic_FADT_check_for_3.0.66v2.patch
total: 0 errors, 0 warnings, 31 lines checked

x2apic_FADT_check_for_3.0.66v2.patch has no obvious style problems and is ready for submission.
----------------------

From: Zhang Lin-Bao <linbao.zhang@xxxxxx>
x86/apic: Work around boot failure on HP ProLiant DL980 G7 Server systems

commit 	cb214ede7657db458fd0b2a25ea0b28dbf900ebc and ea0dcf903e7d76aa5d483d876215fedcfdfe140f upstream.

HP ProLiant DL980 G7 Server boots a regular kernel,
there will be intermittent lost interrupts which could
result in a hang or (in extreme cases) data loss.

The reason is that this system only supports x2apic physical
mode, while the kernel boots with a logical-cluster default
setting.

This bug can be worked around by specifying "x2apic_phys" or
"nox2apic" boot option, but we want to handle this system without
requiring manual workarounds.

BIOS set ACPI_FADT_APIC_PHYSICAL in FADT table.
As all apicids are less than 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.
1. During madt oem check, apic driver is set with xapic logical or
xapic phys driver at first.
2. enable_IR_x2apic() will enable x2apic_mode.
3. if user specify x2apic_phys, x2apic_phys_probe() will install
right x2apic phys driver and use x2apic phys mode.
otherwise will skip and let x2apic_cluster_probe to take over
to install x2apic cluster driver (wrong one) even 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.

Signed-off-by: Stoney Wang <song-bo.wang@xxxxxx>
[ updated the changelog and simplified the code ]
Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
Signed-off-by: Linbao.zhang@xxxxxx
[ make a patch specially for 3.0.66]
Cc: stable@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1360263182-16226-1-git-send-email-yinghai@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>

---
 arch/x86/kernel/apic/x2apic_phys.c |   17 ++++++++++++-----
 1 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/apic/x2apic_phys.c b/arch/x86/kernel/apic/x2apic_phys.c
index f5373df..0f8cb3a 100644
--- a/arch/x86/kernel/apic/x2apic_phys.c
+++ b/arch/x86/kernel/apic/x2apic_phys.c
@@ -20,12 +20,19 @@ static int set_x2apic_phys_mode(char *arg)
 }
 early_param("x2apic_phys", set_x2apic_phys_mode);
 
+static bool x2apic_fadt_phys(void)
+{
+	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 true;
+	}
+	return false;
+}
+
 static int x2apic_acpi_madt_oem_check(char *oem_id, char *oem_table_id)
 {
-	if (x2apic_phys)
-		return x2apic_enabled();
-	else
-		return 0;
+	return x2apic_enabled() && (x2apic_phys || x2apic_fadt_phys());
 }
 
 static void
@@ -108,7 +115,7 @@ 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;
-- 
1.7.9


-- Bob(LinBao Zhang)
HP linux kernel enginner
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