Subject: Re: Subject: [PATCH 1/2] x86: get back 15 vectors

From: Yinghai Lu <[email-masked]>
Date: Mon, 04 Jan 2010 12:06:52 -0800

On 01/04/2010 11:48 AM, H. Peter Anvin wrote:
> [Adding Suresh to the Cc: list]
> 
> On 01/04/2010 11:35 AM, Yinghai Lu wrote:
>>
>> so we can use [0x10, 0x1f]
>>
>> sth like this?
>>
> 
> No!!!
> 
> [0x10, 0x1f] is reserved for exceptions.  We can probably get away with
> stealing *one* vector... presumably at the end (0x1f).  However, we can
> absolutely not use the whole block: 0x10-0x13 is occupied by exceptions
> we already have OS support for (#MF, #AC, #MC, and #XM), and it's pretty
> much guaranteed we'll have more coming.  However, growth is quite slow
> and since this is a kernel-internal vector (not accessible to user
> space) it is not creating an API.
> 
> In other words, we could change FIRST_EXTERNAL_VECTOR to 0x1f, and use
> it for IRQ_MOVE_CLEANUP_VECTOR.  Then use 0x20..0x2f for the legacy vectors.
> 
Subject: [PATCH 1/2] x86: get back 16 vectors

-v2: according to hpa that we could start from 0x1f

Signed-off-by: Yinghai Lu <[email-masked]>

---
 arch/x86/include/asm/irq_vectors.h |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

Index: linux-2.6/arch/x86/include/asm/irq_vectors.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/irq_vectors.h
+++ linux-2.6/arch/x86/include/asm/irq_vectors.h
@@ -30,8 +30,9 @@
 /*
  * IDT vectors usable for external interrupt sources start
  * at 0x20:
+ * hpa said we can start from 0x1f
  */
-#define FIRST_EXTERNAL_VECTOR		0x20
+#define FIRST_EXTERNAL_VECTOR		0x1f
 
 #ifdef CONFIG_X86_32
 # define SYSCALL_VECTOR			0x80
@@ -41,15 +42,15 @@
 #endif
 
 /*
- * Reserve the lowest usable priority level 0x20 - 0x2f for triggering
+ * Reserve the lowest usable priority level 0x1f for triggering
  * cleanup after irq migration.
  */
 #define IRQ_MOVE_CLEANUP_VECTOR		FIRST_EXTERNAL_VECTOR
 
 /*
- * Vectors 0x30-0x3f are used for ISA interrupts.
+ * Vectors 0x20-0x2f are used for ISA interrupts.
  */
-#define IRQ0_VECTOR			(FIRST_EXTERNAL_VECTOR + 0x10)
+#define IRQ0_VECTOR			(FIRST_EXTERNAL_VECTOR + 1)
 
 #define IRQ1_VECTOR			(IRQ0_VECTOR +  1)
 #define IRQ2_VECTOR			(IRQ0_VECTOR +  2)