x86_64: Parsing for ACPI "SAPIC" table

RFC In review Jack Steiner 2 participants 3 messages Mar 24, 2008 – Mar 25, 2008

Subsystems (3)

Memory management x86 ACPI

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Jack Steiner

author

2008-03-24 18:21 UTC #0 lore raw

RFC 4/8 x86_64: Parsing for ACPI "SAPIC" table

Add kernel support for new ACPI "sapic" tables that contain 16-bit APICIDs. This patch simply adds parsing of an optional SAPIC table if present. Otherwise, the traditional local APIC table is used.

Note: the SAPIC table is not a new ACPI table - it exists on other architectures but is not currently recognized by x86_64.

Signed-off-by Jack Steiner <[email protected]>

---
 arch/x86/kernel/acpi/boot.c |   26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

arch/x86/kernel/acpi/boot.c +24 -2

Index: linux/arch/x86/kernel/acpi/boot.c
===================================================================
@@ -261,6 +261,24 @@ acpi_parse_lapic(struct acpi_subtable_he
 }
 
 static int __init
+acpi_parse_sapic(struct acpi_subtable_header *header, const unsigned long end)
+{
+	struct acpi_madt_local_sapic *processor = NULL;
+
+	processor = (struct acpi_madt_local_sapic *)header;
+
+	if (BAD_MADT_ENTRY(processor, end))
+		return -EINVAL;
+
+	acpi_table_print_madt_entry(header);
+
+	mp_register_lapic((processor->id << 8) | processor->eid,/* APIC ID */
+		processor->lapic_flags & ACPI_MADT_ENABLED);	/* Enabled? */
+
+	return 0;
+}
+
+static int __init
 acpi_parse_lapic_addr_ovr(struct acpi_subtable_header * header,
 			  const unsigned long end)
 {

@@ -753,8 +771,12 @@ static int __init acpi_parse_madt_lapic_
 
 	mp_register_lapic_address(acpi_lapic_addr);
 
-	count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC, acpi_parse_lapic,
-				      MAX_APICS);
+	count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_SAPIC,
+				      acpi_parse_sapic, MAX_APICS);
+
+	if (!count)
+		count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC,
+					      acpi_parse_lapic, MAX_APICS);
 	if (!count) {
 		printk(KERN_ERR PREFIX "No LAPIC entries present\n");
 		/* TBD: Cleanup to allow fallback to MPS */

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Len Brown

reviewer

2008-03-25 04:03 UTC #1 lore raw

IIR the x2apic scheme entails using the legacy entries for the first 256 entries, and extended entries for the processors above that, no?

Here we seem to be assuming all lapic or all sapic entries.

-Len

Quoted 61 lines · Jack Steiner

Add kernel support for new ACPI "sapic" tables that contain 16-bit APICIDs. This patch simply adds parsing of an optional SAPIC table if present. Otherwise, the traditional local APIC table is used.

Note: the SAPIC table is not a new ACPI table - it exists on other architectures but is not currently recognized by x86_64.

Signed-off-by Jack Steiner <[email protected]>

---
 arch/x86/kernel/acpi/boot.c |   26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

Index: linux/arch/x86/kernel/acpi/boot.c
===================================================================

arch/x86/kernel/acpi/boot.c +24 -3

@@ -261,6 +261,24 @@ acpi_parse_lapic(struct acpi_subtable_he
 }
 
 static int __init
+acpi_parse_sapic(struct acpi_subtable_header *header, const unsigned long end)
+{
+	struct acpi_madt_local_sapic *processor = NULL;
+
+	processor = (struct acpi_madt_local_sapic *)header;
+
+	if (BAD_MADT_ENTRY(processor, end))
+		return -EINVAL;
+
+	acpi_table_print_madt_entry(header);
+
+	mp_register_lapic((processor->id << 8) | processor->eid,/* APIC ID */
+		processor->lapic_flags & ACPI_MADT_ENABLED);	/* Enabled? */
+
+	return 0;
+}
+
+static int __init
 acpi_parse_lapic_addr_ovr(struct acpi_subtable_header * header,
 			  const unsigned long end)
 {

@@ -753,8 +771,12 @@ static int __init acpi_parse_madt_lapic_
 
 	mp_register_lapic_address(acpi_lapic_addr);
 
-	count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC, acpi_parse_lapic,
-				      MAX_APICS);
+	count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_SAPIC,
+				      acpi_parse_sapic, MAX_APICS);
+
+	if (!count)
+		count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC,
+					      acpi_parse_lapic, MAX_APICS);
 	if (!count) {
 		printk(KERN_ERR PREFIX "No LAPIC entries present\n");
 		/* TBD: Cleanup to allow fallback to MPS */
--

Quoted 5 lines

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Jack Steiner

author

2008-03-25 13:33 UTC #2 lore raw

Quoted 7 lines · Len Brown

IIR the x2apic scheme entails using the legacy entries for the first 256 entries, and extended entries for the processors above that, no?
Here we seem to be assuming all lapic or all sapic entries.
-Len

Correct. That is the way it is currently coded & that is the way that our BIOS creates the tables. Depending on the size of the system, all entries will be either lapic OR all entries will be sapic.

Currently, the BIOS _tries_ to build legacy-compatible tables. It switches into x2apic mode only if APICIDs are too big for legacy mode.

I found a statement in the x2apic spec that appears to support that behavior:

sec 2.11.1 Extended xAPIC Init: BIOS Flow
... There should never be a mixture of legacy and new entries.

However, it is certainly possible that this statement is in conflict with a statement somewhere else.....

Quoted 69 lines · Jack Steiner

Quoted 66 lines
Add kernel support for new ACPI "sapic" tables that contain 16-bit APICIDs. This patch simply adds parsing of an optional SAPIC table if present. Otherwise, the traditional local APIC table is used.
Note: the SAPIC table is not a new ACPI table - it exists on other architectures but is not currently recognized by x86_64.
Signed-off-by Jack Steiner <[email protected]>
---
 arch/x86/kernel/acpi/boot.c |   26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)
Index: linux/arch/x86/kernel/acpi/boot.c
===================================================================
arch/x86/kernel/acpi/boot.c +24 -3
@@ -261,6 +261,24 @@ acpi_parse_lapic(struct acpi_subtable_he
 }
 
 static int __init
+acpi_parse_sapic(struct acpi_subtable_header *header, const unsigned long end)
+{
+	struct acpi_madt_local_sapic *processor = NULL;
+
+	processor = (struct acpi_madt_local_sapic *)header;
+
+	if (BAD_MADT_ENTRY(processor, end))
+		return -EINVAL;
+
+	acpi_table_print_madt_entry(header);
+
+	mp_register_lapic((processor->id << 8) | processor->eid,/* APIC ID */
+		processor->lapic_flags & ACPI_MADT_ENABLED);	/* Enabled? */
+
+	return 0;
+}
+
+static int __init
 acpi_parse_lapic_addr_ovr(struct acpi_subtable_header * header,
 			  const unsigned long end)
 {
@@ -753,8 +771,12 @@ static int __init acpi_parse_madt_lapic_
 
 	mp_register_lapic_address(acpi_lapic_addr);
 
-	count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC, acpi_parse_lapic,
-				      MAX_APICS);
+	count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_SAPIC,
+				      acpi_parse_sapic, MAX_APICS);
+
+	if (!count)
+		count = acpi_table_parse_madt(ACPI_MADT_TYPE_LOCAL_APIC,
+					      acpi_parse_lapic, MAX_APICS);
 	if (!count) {
 		printk(KERN_ERR PREFIX "No LAPIC entries present\n");
 		/* TBD: Cleanup to allow fallback to MPS */
--
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Signature · 11 lines

Thanks

Jack Steiner ([email protected])          651-683-5302
Principal Engineer                      SGI - Silicon Graphics, Inc.


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