linux-kernel - [PATCH v4] x86, apic: Check fadt x2apic phys in x2apic_phys

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Message-Id: <1360263182-16226-1-git-send-email-yinghai@kernel.org>
Date:	Thu,  7 Feb 2013 10:53:02 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Cc:	linux-kernel@...r.kernel.org, Stoney Wang <song-bo.wang@...com>,
	Yinghai Lu <yinghai@...nel.org>, stable@...nel.org
Subject: [PATCH v4] x86, apic: Check fadt x2apic phys in x2apic_phys_probe()

From: Stoney Wang <song-bo.wang@...com>

When a 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.

-v3: update the change according to Ingo.
-v4: merge changelog from Ingo.

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