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[patch 2/7] x86/lguest: Do not setup unused irq vectors

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  [patch 2/7] x86/lguest: Do not setup unused irq vectors Thomas Gleixner <tglx@linutronix.de> - 2015-08-02 22:40 +0200
    Re: [patch 2/7] x86/lguest: Do not setup unused irq vectors Rusty Russell <rusty@rustcorp.com.au> - 2015-08-03 05:00 +0200
      Re: [patch 2/7] x86/lguest: Do not setup unused irq vectors Thomas Gleixner <tglx@linutronix.de> - 2015-08-03 11:50 +0200
        Re: [patch 2/7] x86/lguest: Do not setup unused irq vectors Rusty Russell <rusty@rustcorp.com.au> - 2015-08-04 06:40 +0200
          [PATCH 2/2] x86/lguest: Do not setup unused irq vectors Rusty Russell <rusty@rustcorp.com.au> - 2015-08-04 06:40 +0200
          [PATCH 1/2] x86/lguest: clean up lguest_setup_irq. Rusty Russell <rusty@rustcorp.com.au> - 2015-08-04 06:40 +0200

#1198454 — [patch 2/7] x86/lguest: Do not setup unused irq vectors

No point in assigning the interrupt vectors if there is no interrupt
chip installed. Move it to lguest_setup_irq().

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
---
 arch/x86/lguest/boot.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

Index: tip/arch/x86/lguest/boot.c
===================================================================
--- tip.orig/arch/x86/lguest/boot.c
+++ tip/arch/x86/lguest/boot.c
@@ -855,17 +855,13 @@ static void lguest_disable_irq(struct pc
 
 /*
  * This sets up the Interrupt Descriptor Table (IDT) entry for each hardware
- * interrupt (except 128, which is used for system calls), and then tells the
- * Linux infrastructure that each interrupt is controlled by our level-based
- * lguest interrupt controller.
+ * interrupt (except 128, which is used for system calls).
  */
 static void __init lguest_init_IRQ(void)
 {
 	unsigned int i;
 
 	for (i = FIRST_EXTERNAL_VECTOR; i < FIRST_SYSTEM_VECTOR; i++) {
-		/* Some systems map "vectors" to interrupts weirdly.  Not us! */
-		__this_cpu_write(vector_irq[i], i - FIRST_EXTERNAL_VECTOR);
 		if (i != IA32_SYSCALL_VECTOR)
 			set_intr_gate(i, irq_entries_start +
 					8 * (i - FIRST_EXTERNAL_VECTOR));
@@ -893,8 +889,15 @@ int lguest_setup_irq(unsigned int irq)
 	if (err < 0 && err != -EEXIST)
 		return err;
 
+	/*
+	 * Tell the Linux infrastructure that the interrupt is
+	 * controlled by our level-based lguest interrupt controller.
+	 */
 	irq_set_chip_and_handler_name(irq, &lguest_irq_controller,
 				      handle_level_irq, "level");
+
+	/* Some systems map "vectors" to interrupts weirdly.  Not us! */
+	__this_cpu_write(vector_irq[FIRST_EXTERNAL_VECTOR + irq, irq);
 	return 0;
 }
 


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#1198506

Thomas Gleixner <tglx@linutronix.de> writes:
> No point in assigning the interrupt vectors if there is no interrupt
> chip installed. Move it to lguest_setup_irq().
>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: Rusty Russell <rusty@rustcorp.com.au>
> ---
>  arch/x86/lguest/boot.c |   13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> Index: tip/arch/x86/lguest/boot.c
> ===================================================================
> --- tip.orig/arch/x86/lguest/boot.c
> +++ tip/arch/x86/lguest/boot.c
> @@ -855,17 +855,13 @@ static void lguest_disable_irq(struct pc
>  
>  /*
>   * This sets up the Interrupt Descriptor Table (IDT) entry for each hardware
> - * interrupt (except 128, which is used for system calls), and then tells the
> - * Linux infrastructure that each interrupt is controlled by our level-based
> - * lguest interrupt controller.
> + * interrupt (except 128, which is used for system calls).
>   */
>  static void __init lguest_init_IRQ(void)
>  {
>  	unsigned int i;
>  
>  	for (i = FIRST_EXTERNAL_VECTOR; i < FIRST_SYSTEM_VECTOR; i++) {
> -		/* Some systems map "vectors" to interrupts weirdly.  Not us! */
> -		__this_cpu_write(vector_irq[i], i - FIRST_EXTERNAL_VECTOR);
>  		if (i != IA32_SYSCALL_VECTOR)
>  			set_intr_gate(i, irq_entries_start +
>  					8 * (i - FIRST_EXTERNAL_VECTOR));
> @@ -893,8 +889,15 @@ int lguest_setup_irq(unsigned int irq)
>  	if (err < 0 && err != -EEXIST)
>  		return err;
>  
> +	/*
> +	 * Tell the Linux infrastructure that the interrupt is
> +	 * controlled by our level-based lguest interrupt controller.
> +	 */
>  	irq_set_chip_and_handler_name(irq, &lguest_irq_controller,
>  				      handle_level_irq, "level");
> +
> +	/* Some systems map "vectors" to interrupts weirdly.  Not us! */
> +	__this_cpu_write(vector_irq[FIRST_EXTERNAL_VECTOR + irq, irq);

Missing ].

Then it doesn't work:

[    3.832028] do_IRQ: 0.33 No irq handler for vector (irq -1)
[    3.832028] do_IRQ: 0.33 No irq handler for vector (irq -1)
[    3.832028] do_IRQ: 0.33 No irq handler for vector (irq -1)
[    3.839983] do_IRQ: 0.33 No irq handler for vector (irq -1)
[    3.840026] do_IRQ: 0.33 No irq handler for vector (irq -1)
[    3.840026] do_IRQ: 0.33 No irq handler for vector (irq -1)
[    3.840026] do_IRQ: 0.33 No irq handler for vector (irq -1)
[    3.848349] do_IRQ: 0.33 No irq handler for vector (irq -1)
[    3.848349] do_IRQ: 0.33 No irq handler for vector (irq -1)
[    3.848349] do_IRQ: 0.33 No irq handler for vector (irq -1)
[    4.056027] brd: module loaded
[    4.156025] loop: module loaded

<hit return>

[   17.712169] do_IRQ: 4 callbacks suppressed
[   17.712169] do_IRQ: 0.33 No irq handler for vector (irq -1)
[   17.720462] do_IRQ: 0.33 No irq handler for vector (irq -1)
[   17.720462] do_IRQ: 0.33 No irq handler for vector (irq -1)
[   17.729129] do_IRQ: 0.33 No irq handler for vector (irq -1)
[   17.729129] do_IRQ: 0.33 No irq handler for vector (irq -1)
[   17.736523] do_IRQ: 0.33 No irq handler for vector (irq -1)
[   17.736523] do_IRQ: 0.33 No irq handler for vector (irq -1)
[   17.744288] do_IRQ: 0.33 No irq handler for vector (irq -1)
[   17.744288] do_IRQ: 0.33 No irq handler for vector (irq -1)
[   17.751889] do_IRQ: 0.33 No irq handler for vector (irq -1)

You broke interrupts :(

Cheers,
Rusty.
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#1198679

On Mon, 3 Aug 2015, Rusty Russell wrote:
> Thomas Gleixner <tglx@linutronix.de> writes:
> > +
> > +	/* Some systems map "vectors" to interrupts weirdly.  Not us! */
> > +	__this_cpu_write(vector_irq[FIRST_EXTERNAL_VECTOR + irq, irq);
> 
> Missing ].

Doh.

> [   17.751889] do_IRQ: 0.33 No irq handler for vector (irq -1)
> 
> You broke interrupts :(

Right, because I missed the other place which fiddles with
interrupts. Does the patch below fix the issue?

Thanks,

	tglx
---------------->
Index: tip/arch/x86/lguest/boot.c
===================================================================
--- tip.orig/arch/x86/lguest/boot.c
+++ tip/arch/x86/lguest/boot.c
@@ -841,8 +841,7 @@ static int lguest_enable_irq(struct pci_
 
 	/* We literally use the PCI interrupt line as the irq number. */
 	pci_read_config_byte(dev, PCI_INTERRUPT_LINE, &line);
-	irq_set_chip_and_handler_name(line, &lguest_irq_controller,
-				      handle_level_irq, "level");
+	lguest_setup_irq(line);
 	dev->irq = line;
 	return 0;
 }




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#1199407

Thomas Gleixner <tglx@linutronix.de> writes:
> On Mon, 3 Aug 2015, Rusty Russell wrote:
>> Thomas Gleixner <tglx@linutronix.de> writes:
>> > +
>> > +	/* Some systems map "vectors" to interrupts weirdly.  Not us! */
>> > +	__this_cpu_write(vector_irq[FIRST_EXTERNAL_VECTOR + irq, irq);
>> 
>> Missing ].
>
> Doh.
>
>> [   17.751889] do_IRQ: 0.33 No irq handler for vector (irq -1)
>> 
>> You broke interrupts :(
>
> Right, because I missed the other place which fiddles with
> interrupts. Does the patch below fix the issue?

Yep.  I added error handling.

I reworked it into two patches: one which staticizes lguest_setup_irq()
and moves it up, the other of which applies your changes.

Will post, you can take them...

Thanks,
Rusty.
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#1199408 — [PATCH 2/2] x86/lguest: Do not setup unused irq vectors

From: Thomas Gleixner <tglx@linutronix.de>

No point in assigning the interrupt vectors if there is no interrupt
chip installed. Move it to lguest_setup_irq().

(And call it from lguest_enable_irq).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> (fixed typo)
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 arch/x86/lguest/boot.c | 22 +++++++++++++---------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index f38b7e8a88d2..2566c97c01c8 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -850,21 +850,29 @@ static int lguest_setup_irq(unsigned int irq)
 	if (err < 0 && err != -EEXIST)
 		return err;
 
+	/*
+	 * Tell the Linux infrastructure that the interrupt is
+	 * controlled by our level-based lguest interrupt controller.
+	 */
 	irq_set_chip_and_handler_name(irq, &lguest_irq_controller,
 				      handle_level_irq, "level");
+
+	/* Some systems map "vectors" to interrupts weirdly.  Not us! */
+	__this_cpu_write(vector_irq[FIRST_EXTERNAL_VECTOR + irq], irq);
 	return 0;
 }
 
 static int lguest_enable_irq(struct pci_dev *dev)
 {
+	int err;
 	u8 line = 0;
 
 	/* We literally use the PCI interrupt line as the irq number. */
 	pci_read_config_byte(dev, PCI_INTERRUPT_LINE, &line);
-	irq_set_chip_and_handler_name(line, &lguest_irq_controller,
-				      handle_level_irq, "level");
-	dev->irq = line;
-	return 0;
+	err = lguest_setup_irq(line);
+	if (!err)
+		dev->irq = line;
+	return err;
 }
 
 /* We don't do hotplug PCI, so this shouldn't be called. */
@@ -875,17 +883,13 @@ static void lguest_disable_irq(struct pci_dev *dev)
 
 /*
  * This sets up the Interrupt Descriptor Table (IDT) entry for each hardware
- * interrupt (except 128, which is used for system calls), and then tells the
- * Linux infrastructure that each interrupt is controlled by our level-based
- * lguest interrupt controller.
+ * interrupt (except 128, which is used for system calls).
  */
 static void __init lguest_init_IRQ(void)
 {
 	unsigned int i;
 
 	for (i = FIRST_EXTERNAL_VECTOR; i < FIRST_SYSTEM_VECTOR; i++) {
-		/* Some systems map "vectors" to interrupts weirdly.  Not us! */
-		__this_cpu_write(vector_irq[i], i - FIRST_EXTERNAL_VECTOR);
 		if (i != IA32_SYSCALL_VECTOR)
 			set_intr_gate(i, irq_entries_start +
 					8 * (i - FIRST_EXTERNAL_VECTOR));
-- 
2.1.4

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#1199409 — [PATCH 1/2] x86/lguest: clean up lguest_setup_irq.

We make it static and hoist it higher in the file for the next patch.
We also give a nice panic if it fails during boot.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
 arch/x86/lguest/boot.c | 43 ++++++++++++++++++++++---------------------
 1 file changed, 22 insertions(+), 21 deletions(-)

diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 433e5a7dd37f..f38b7e8a88d2 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -835,6 +835,26 @@ static struct irq_chip lguest_irq_controller = {
 	.irq_unmask	= enable_lguest_irq,
 };
 
+/*
+ * Interrupt descriptors are allocated as-needed, but low-numbered ones are
+ * reserved by the generic x86 code.  So we ignore irq_alloc_desc_at if it
+ * tells us the irq is already used: other errors (ie. ENOMEM) we take
+ * seriously.
+ */
+static int lguest_setup_irq(unsigned int irq)
+{
+	int err;
+
+	/* Returns -ve error or vector number. */
+	err = irq_alloc_desc_at(irq, 0);
+	if (err < 0 && err != -EEXIST)
+		return err;
+
+	irq_set_chip_and_handler_name(irq, &lguest_irq_controller,
+				      handle_level_irq, "level");
+	return 0;
+}
+
 static int lguest_enable_irq(struct pci_dev *dev)
 {
 	u8 line = 0;
@@ -879,26 +899,6 @@ static void __init lguest_init_IRQ(void)
 }
 
 /*
- * Interrupt descriptors are allocated as-needed, but low-numbered ones are
- * reserved by the generic x86 code.  So we ignore irq_alloc_desc_at if it
- * tells us the irq is already used: other errors (ie. ENOMEM) we take
- * seriously.
- */
-int lguest_setup_irq(unsigned int irq)
-{
-	int err;
-
-	/* Returns -ve error or vector number. */
-	err = irq_alloc_desc_at(irq, 0);
-	if (err < 0 && err != -EEXIST)
-		return err;
-
-	irq_set_chip_and_handler_name(irq, &lguest_irq_controller,
-				      handle_level_irq, "level");
-	return 0;
-}
-
-/*
  * Time.
  *
  * It would be far better for everyone if the Guest had its own clock, but
@@ -1028,7 +1028,8 @@ static void lguest_time_irq(unsigned int irq, struct irq_desc *desc)
 static void lguest_time_init(void)
 {
 	/* Set up the timer interrupt (0) to go to our simple timer routine */
-	lguest_setup_irq(0);
+	if (lguest_setup_irq(0) != 0)
+		panic("Could not set up timer irq");
 	irq_set_handler(0, lguest_time_irq);
 
 	clocksource_register_hz(&lguest_clock, NSEC_PER_SEC);
-- 
2.1.4

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