[PATCH] x86: increase interrupt vector range

Remove the limit of 256 interrupt vectors by changing the value stored in
orig_{e,r}ax to be the complemented interrupt vector.  The orig_{e,r}ax
needs to be < 0 to allow the signal code to distinguish between return from
interrupt and return from syscall.  With this change applied, NR_IRQS can
be > 256.

Xen extends the IRQ numbering space to include room for dynamically
allocated virtual interrupts (in the range 256-511), which requires a more
permissive interface to do_IRQ.

Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: "Protasevich, Natalie" <Natalie.Protasevich@UNISYS.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

6 files changed, 10 insertions, 10 deletions

diff --git a/arch/i386/kernel/entry.S b/arch/i386/kernel/entry.S
index e6e4506e749a..8713e0248a0b 100644
--- a/arch/i386/kernel/entry.S
+++ b/arch/i386/kernel/entry.S
@@ -515,7 +515,7 @@ ENTRY(irq_entries_start)
  .if vector
         CFI_ADJUST_CFA_OFFSET -4
  .endif
-1:      pushl $vector-256
+1:      pushl $~(vector)
         CFI_ADJUST_CFA_OFFSET 4
         jmp common_interrupt
 .data
@@ -535,7 +535,7 @@ common_interrupt:
 #define BUILD_INTERRUPT(name, nr)       \
 ENTRY(name)                             \
         RING0_INT_FRAME;                \
-        pushl $nr-256;                  \
+        pushl $~(nr);                   \
         CFI_ADJUST_CFA_OFFSET 4;        \
         SAVE_ALL;                       \
         movl %esp,%eax;                 \
diff --git a/arch/i386/kernel/irq.c b/arch/i386/kernel/irq.c
index 061533e0cb5e..586b15f6741f 100644
--- a/arch/i386/kernel/irq.c
+++ b/arch/i386/kernel/irq.c
@@ -53,8 +53,8 @@ static union irq_ctx *softirq_ctx[NR_CPUS] __read_mostly;
  */
 fastcall unsigned int do_IRQ(struct pt_regs *regs)
 {       
-        /* high bits used in ret_from_ code */
-        int irq = regs->orig_eax & 0xff;
+        /* high bit used in ret_from_ code */
+        int irq = ~regs->orig_eax;
 #ifdef CONFIG_4KSTACKS
         union irq_ctx *curctx, *irqctx;
         u32 *isp;
diff --git a/arch/x86_64/kernel/entry.S b/arch/x86_64/kernel/entry.S
index 7290e72b9a34..22cac4487b57 100644
--- a/arch/x86_64/kernel/entry.S
+++ b/arch/x86_64/kernel/entry.S
@@ -588,7 +588,7 @@ END(common_interrupt)
  */             
         .macro apicinterrupt num,func
         INTR_FRAME
-        pushq $\num-256
+        pushq $~(\num)
         CFI_ADJUST_CFA_OFFSET 8
         interrupt \func
         jmp ret_from_intr
diff --git a/arch/x86_64/kernel/irq.c b/arch/x86_64/kernel/irq.c
index 59518d4d4358..3be0a7e4bf08 100644
--- a/arch/x86_64/kernel/irq.c
+++ b/arch/x86_64/kernel/irq.c
@@ -115,8 +115,8 @@ skip:
  */
 asmlinkage unsigned int do_IRQ(struct pt_regs *regs)
 {       
-        /* high bits used in ret_from_ code  */
-        unsigned irq = regs->orig_rax & 0xff;
+        /* high bit used in ret_from_ code  */
+        unsigned irq = ~regs->orig_rax;
 
         exit_idle();
         irq_enter();
diff --git a/arch/x86_64/kernel/smp.c b/arch/x86_64/kernel/smp.c
index acee4bc3f6fa..5a1c0a3bf872 100644
--- a/arch/x86_64/kernel/smp.c
+++ b/arch/x86_64/kernel/smp.c
@@ -135,10 +135,10 @@ asmlinkage void smp_invalidate_interrupt(struct pt_regs *regs)
 
         cpu = smp_processor_id();
         /*
-         * orig_rax contains the interrupt vector - 256.
+         * orig_rax contains the negated interrupt vector.
          * Use that to determine where the sender put the data.
          */
-        sender = regs->orig_rax + 256 - INVALIDATE_TLB_VECTOR_START;
+        sender = ~regs->orig_rax - INVALIDATE_TLB_VECTOR_START;
         f = &per_cpu(flush_state, sender);
 
         if (!cpu_isset(cpu, f->flush_cpumask))
diff --git a/include/asm-x86_64/hw_irq.h b/include/asm-x86_64/hw_irq.h
index 1b2ac55d3204..931877462788 100644
--- a/include/asm-x86_64/hw_irq.h
+++ b/include/asm-x86_64/hw_irq.h
@@ -124,7 +124,7 @@ asmlinkage void IRQ_NAME(nr); \
 __asm__( \
 "\n.p2align\n" \
 "IRQ" #nr "_interrupt:\n\t" \
-        "push $" #nr "-256 ; " \
+        "push $~(" #nr ") ; " \
         "jmp common_interrupt");
 
 #if defined(CONFIG_X86_IO_APIC)