Patch "x86/irq: Probe for PIC presence before allocating descs for legacy IRQs" has been added to the 4.3-stable tree

Patch "x86/irq: Probe for PIC presence before allocating descs for legacy IRQs" has been added to the 4.3-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    x86/irq: Probe for PIC presence before allocating descs for legacy IRQs

to the 4.3-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     x86-irq-probe-for-pic-presence-before-allocating-descs-for-legacy-irqs.patch
and it can be found in the queue-4.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From 8c058b0b9c34d8c8d7912880956543769323e2d8 Mon Sep 17 00:00:00 2001
From: Vitaly Kuznetsov <vkuznets@redhat.com>
Date: Tue, 3 Nov 2015 10:40:14 +0100
Subject: x86/irq: Probe for PIC presence before allocating descs for legacy IRQs

From: Vitaly Kuznetsov <vkuznets@redhat.com>

commit 8c058b0b9c34d8c8d7912880956543769323e2d8 upstream.

Commit d32932d02e18 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain
interfaces") brought a regression for Hyper-V Gen2 instances. These
instances don't have i8259 legacy PIC but they use legacy IRQs for serial
port, rtc, and acpi. With this commit included we end up with these IRQs
not initialized. Earlier, there was a special workaround for legacy IRQs
in mp_map_pin_to_irq() doing mp_irqdomain_map() without looking at
nr_legacy_irqs() and now we fail in __irq_domain_alloc_irqs() when
irq_domain_alloc_descs() returns -EEXIST.

The essence of the issue seems to be that early_irq_init() calls
arch_probe_nr_irqs() to figure out the number of legacy IRQs before
we probe for i8259 and gets 16. Later when init_8259A() is called we switch
to NULL legacy PIC and nr_legacy_irqs() starts to return 0 but we already
have 16 descs allocated.

Solve the issue by separating i8259 probe from init and calling it in
arch_probe_nr_irqs() before we actually use nr_legacy_irqs() information.

Fixes: d32932d02e18 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain interfaces")
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Jiang Liu <jiang.liu@linux.intel.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Link: http://lkml.kernel.org/r/1446543614-3621-1-git-send-email-vkuznets@redhat.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/x86/include/asm/i8259.h  |    1 +
 arch/x86/kernel/apic/vector.c |    6 +++++-
 arch/x86/kernel/i8259.c       |   29 +++++++++++++++++++++--------
 3 files changed, 27 insertions(+), 9 deletions(-)

--- a/arch/x86/include/asm/i8259.h
+++ b/arch/x86/include/asm/i8259.h
@@ -60,6 +60,7 @@ struct legacy_pic {
 	void (*mask_all)(void);
 	void (*restore_mask)(void);
 	void (*init)(int auto_eoi);
+	int (*probe)(void);
 	int (*irq_pending)(unsigned int irq);
 	void (*make_irq)(unsigned int irq);
 };
--- a/arch/x86/kernel/apic/vector.c
+++ b/arch/x86/kernel/apic/vector.c
@@ -361,7 +361,11 @@ int __init arch_probe_nr_irqs(void)
 	if (nr < nr_irqs)
 		nr_irqs = nr;
 
-	return nr_legacy_irqs();
+	/*
+	 * We don't know if PIC is present at this point so we need to do
+	 * probe() to get the right number of legacy IRQs.
+	 */
+	return legacy_pic->probe();
 }
 
 #ifdef	CONFIG_X86_IO_APIC
--- a/arch/x86/kernel/i8259.c
+++ b/arch/x86/kernel/i8259.c
@@ -295,16 +295,11 @@ static void unmask_8259A(void)
 	raw_spin_unlock_irqrestore(&i8259A_lock, flags);
 }
 
-static void init_8259A(int auto_eoi)
+static int probe_8259A(void)
 {
 	unsigned long flags;
 	unsigned char probe_val = ~(1 << PIC_CASCADE_IR);
 	unsigned char new_val;
-
-	i8259A_auto_eoi = auto_eoi;
-
-	raw_spin_lock_irqsave(&i8259A_lock, flags);
-
 	/*
 	 * Check to see if we have a PIC.
 	 * Mask all except the cascade and read
@@ -312,16 +307,28 @@ static void init_8259A(int auto_eoi)
 	 * have a PIC, we will read 0xff as opposed to the
 	 * value we wrote.
 	 */
+	raw_spin_lock_irqsave(&i8259A_lock, flags);
+
 	outb(0xff, PIC_SLAVE_IMR);	/* mask all of 8259A-2 */
 	outb(probe_val, PIC_MASTER_IMR);
 	new_val = inb(PIC_MASTER_IMR);
 	if (new_val != probe_val) {
 		printk(KERN_INFO "Using NULL legacy PIC\n");
 		legacy_pic = &null_legacy_pic;
-		raw_spin_unlock_irqrestore(&i8259A_lock, flags);
-		return;
 	}
 
+	raw_spin_unlock_irqrestore(&i8259A_lock, flags);
+	return nr_legacy_irqs();
+}
+
+static void init_8259A(int auto_eoi)
+{
+	unsigned long flags;
+
+	i8259A_auto_eoi = auto_eoi;
+
+	raw_spin_lock_irqsave(&i8259A_lock, flags);
+
 	outb(0xff, PIC_MASTER_IMR);	/* mask all of 8259A-1 */
 
 	/*
@@ -379,6 +386,10 @@ static int legacy_pic_irq_pending_noop(u
 {
 	return 0;
 }
+static int legacy_pic_probe(void)
+{
+	return 0;
+}
 
 struct legacy_pic null_legacy_pic = {
 	.nr_legacy_irqs = 0,
@@ -388,6 +399,7 @@ struct legacy_pic null_legacy_pic = {
 	.mask_all = legacy_pic_noop,
 	.restore_mask = legacy_pic_noop,
 	.init = legacy_pic_int_noop,
+	.probe = legacy_pic_probe,
 	.irq_pending = legacy_pic_irq_pending_noop,
 	.make_irq = legacy_pic_uint_noop,
 };
@@ -400,6 +412,7 @@ struct legacy_pic default_legacy_pic = {
 	.mask_all = mask_8259A,
 	.restore_mask = unmask_8259A,
 	.init = init_8259A,
+	.probe = probe_8259A,
 	.irq_pending = i8259A_irq_pending,
 	.make_irq = make_8259A_irq,
 };


Patches currently in stable-queue which might be from vkuznets@redhat.com are

queue-4.3/x86-irq-probe-for-pic-presence-before-allocating-descs-for-legacy-irqs.patch

Re: Patch "x86/irq: Probe for PIC presence before allocating descs for legacy IRQs" has been added to the 4.3-stable tree

[Vitaly Kuznetsov]

<gregkh@linuxfoundation.org> writes:

> This is a note to let you know that I've just added the patch titled
>
>     x86/irq: Probe for PIC presence before allocating descs for legacy IRQs
>
> to the 4.3-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
>
> The filename of the patch is:
>      x86-irq-probe-for-pic-presence-before-allocating-descs-for-legacy-irqs.patch
> and it can be found in the queue-4.3 subdirectory.
>
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <stable@vger.kernel.org> know about it.

This commit is known for breaking Xen PV guests, the breakage is fixed
with the following:

commit b4ff8389ed14b849354b59ce9b360bdefcdbf99c
Author: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Date:   Fri Nov 20 11:25:04 2015 -0500

    xen/events: Always allocate legacy interrupts on PV guests

I suggest we include this commit as well. Same for 4.2-stable tree.

>
> From 8c058b0b9c34d8c8d7912880956543769323e2d8 Mon Sep 17 00:00:00 2001
> From: Vitaly Kuznetsov <vkuznets@redhat.com>
> Date: Tue, 3 Nov 2015 10:40:14 +0100
> Subject: x86/irq: Probe for PIC presence before allocating descs for legacy IRQs
>
> From: Vitaly Kuznetsov <vkuznets@redhat.com>
>
> commit 8c058b0b9c34d8c8d7912880956543769323e2d8 upstream.
>
> Commit d32932d02e18 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain
> interfaces") brought a regression for Hyper-V Gen2 instances. These
> instances don't have i8259 legacy PIC but they use legacy IRQs for serial
> port, rtc, and acpi. With this commit included we end up with these IRQs
> not initialized. Earlier, there was a special workaround for legacy IRQs
> in mp_map_pin_to_irq() doing mp_irqdomain_map() without looking at
> nr_legacy_irqs() and now we fail in __irq_domain_alloc_irqs() when
> irq_domain_alloc_descs() returns -EEXIST.
>
> The essence of the issue seems to be that early_irq_init() calls
> arch_probe_nr_irqs() to figure out the number of legacy IRQs before
> we probe for i8259 and gets 16. Later when init_8259A() is called we switch
> to NULL legacy PIC and nr_legacy_irqs() starts to return 0 but we already
> have 16 descs allocated.
>
> Solve the issue by separating i8259 probe from init and calling it in
> arch_probe_nr_irqs() before we actually use nr_legacy_irqs() information.
>
> Fixes: d32932d02e18 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain interfaces")
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> Cc: Jiang Liu <jiang.liu@linux.intel.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> Link: http://lkml.kernel.org/r/1446543614-3621-1-git-send-email-vkuznets@redhat.com
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> ---
>  arch/x86/include/asm/i8259.h  |    1 +
>  arch/x86/kernel/apic/vector.c |    6 +++++-
>  arch/x86/kernel/i8259.c       |   29 +++++++++++++++++++++--------
>  3 files changed, 27 insertions(+), 9 deletions(-)
>
> --- a/arch/x86/include/asm/i8259.h
> +++ b/arch/x86/include/asm/i8259.h
> @@ -60,6 +60,7 @@ struct legacy_pic {
>  	void (*mask_all)(void);
>  	void (*restore_mask)(void);
>  	void (*init)(int auto_eoi);
> +	int (*probe)(void);
>  	int (*irq_pending)(unsigned int irq);
>  	void (*make_irq)(unsigned int irq);
>  };
> --- a/arch/x86/kernel/apic/vector.c
> +++ b/arch/x86/kernel/apic/vector.c
> @@ -361,7 +361,11 @@ int __init arch_probe_nr_irqs(void)
>  	if (nr < nr_irqs)
>  		nr_irqs = nr;
>
> -	return nr_legacy_irqs();
> +	/*
> +	 * We don't know if PIC is present at this point so we need to do
> +	 * probe() to get the right number of legacy IRQs.
> +	 */
> +	return legacy_pic->probe();
>  }
>
>  #ifdef	CONFIG_X86_IO_APIC
> --- a/arch/x86/kernel/i8259.c
> +++ b/arch/x86/kernel/i8259.c
> @@ -295,16 +295,11 @@ static void unmask_8259A(void)
>  	raw_spin_unlock_irqrestore(&i8259A_lock, flags);
>  }
>
> -static void init_8259A(int auto_eoi)
> +static int probe_8259A(void)
>  {
>  	unsigned long flags;
>  	unsigned char probe_val = ~(1 << PIC_CASCADE_IR);
>  	unsigned char new_val;
> -
> -	i8259A_auto_eoi = auto_eoi;
> -
> -	raw_spin_lock_irqsave(&i8259A_lock, flags);
> -
>  	/*
>  	 * Check to see if we have a PIC.
>  	 * Mask all except the cascade and read
> @@ -312,16 +307,28 @@ static void init_8259A(int auto_eoi)
>  	 * have a PIC, we will read 0xff as opposed to the
>  	 * value we wrote.
>  	 */
> +	raw_spin_lock_irqsave(&i8259A_lock, flags);
> +
>  	outb(0xff, PIC_SLAVE_IMR);	/* mask all of 8259A-2 */
>  	outb(probe_val, PIC_MASTER_IMR);
>  	new_val = inb(PIC_MASTER_IMR);
>  	if (new_val != probe_val) {
>  		printk(KERN_INFO "Using NULL legacy PIC\n");
>  		legacy_pic = &null_legacy_pic;
> -		raw_spin_unlock_irqrestore(&i8259A_lock, flags);
> -		return;
>  	}
>
> +	raw_spin_unlock_irqrestore(&i8259A_lock, flags);
> +	return nr_legacy_irqs();
> +}
> +
> +static void init_8259A(int auto_eoi)
> +{
> +	unsigned long flags;
> +
> +	i8259A_auto_eoi = auto_eoi;
> +
> +	raw_spin_lock_irqsave(&i8259A_lock, flags);
> +
>  	outb(0xff, PIC_MASTER_IMR);	/* mask all of 8259A-1 */
>
>  	/*
> @@ -379,6 +386,10 @@ static int legacy_pic_irq_pending_noop(u
>  {
>  	return 0;
>  }
> +static int legacy_pic_probe(void)
> +{
> +	return 0;
> +}
>
>  struct legacy_pic null_legacy_pic = {
>  	.nr_legacy_irqs = 0,
> @@ -388,6 +399,7 @@ struct legacy_pic null_legacy_pic = {
>  	.mask_all = legacy_pic_noop,
>  	.restore_mask = legacy_pic_noop,
>  	.init = legacy_pic_int_noop,
> +	.probe = legacy_pic_probe,
>  	.irq_pending = legacy_pic_irq_pending_noop,
>  	.make_irq = legacy_pic_uint_noop,
>  };
> @@ -400,6 +412,7 @@ struct legacy_pic default_legacy_pic = {
>  	.mask_all = mask_8259A,
>  	.restore_mask = unmask_8259A,
>  	.init = init_8259A,
> +	.probe = probe_8259A,
>  	.irq_pending = i8259A_irq_pending,
>  	.make_irq = make_8259A_irq,
>  };
>
> Patches currently in stable-queue which might be from vkuznets@redhat.com are
>
> queue-4.3/x86-irq-probe-for-pic-presence-before-allocating-descs-for-legacy-irqs.patch

-- 
  Vitaly

Re: [Xen-devel] Patch "x86/irq: Probe for PIC presence before allocating descs for legacy IRQs" has been added to the 4.3-stable tree

[Sander Eikelenboom]

Monday, December 7, 2015, 1:54:35 PM, you wrote:

> <gregkh@linuxfoundation.org> writes:

>> This is a note to let you know that I've just added the patch titled
>>
>>     x86/irq: Probe for PIC presence before allocating descs for legacy IRQs
>>
>> to the 4.3-stable tree which can be found at:
>>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
>>
>> The filename of the patch is:
>>      x86-irq-probe-for-pic-presence-before-allocating-descs-for-legacy-irqs.patch
>> and it can be found in the queue-4.3 subdirectory.
>>
>> If you, or anyone else, feels it should not be added to the stable tree,
>> please let <stable@vger.kernel.org> know about it.

> This commit is known for breaking Xen PV guests, the breakage is fixed
> with the following:

> commit b4ff8389ed14b849354b59ce9b360bdefcdbf99c
> Author: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Date:   Fri Nov 20 11:25:04 2015 -0500

>     xen/events: Always allocate legacy interrupts on PV guests

> I suggest we include this commit as well. Same for 4.2-stable tree.

Which in turn causes the problem described in:
"Xen-devel] [PATCHv1] x86: rtc_cmos platform device requires legacy irqs"
http://lkml.iu.edu/hypermail/linux/kernel/1512.0/02430.html

for which a patch is still pending a discussion about the right way to fix it.

--
Sander

>>
>> From 8c058b0b9c34d8c8d7912880956543769323e2d8 Mon Sep 17 00:00:00 2001
>> From: Vitaly Kuznetsov <vkuznets@redhat.com>
>> Date: Tue, 3 Nov 2015 10:40:14 +0100
>> Subject: x86/irq: Probe for PIC presence before allocating descs for legacy IRQs
>>
>> From: Vitaly Kuznetsov <vkuznets@redhat.com>
>>
>> commit 8c058b0b9c34d8c8d7912880956543769323e2d8 upstream.
>>
>> Commit d32932d02e18 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain
>> interfaces") brought a regression for Hyper-V Gen2 instances. These
>> instances don't have i8259 legacy PIC but they use legacy IRQs for serial
>> port, rtc, and acpi. With this commit included we end up with these IRQs
>> not initialized. Earlier, there was a special workaround for legacy IRQs
>> in mp_map_pin_to_irq() doing mp_irqdomain_map() without looking at
>> nr_legacy_irqs() and now we fail in __irq_domain_alloc_irqs() when
>> irq_domain_alloc_descs() returns -EEXIST.
>>
>> The essence of the issue seems to be that early_irq_init() calls
>> arch_probe_nr_irqs() to figure out the number of legacy IRQs before
>> we probe for i8259 and gets 16. Later when init_8259A() is called we switch
>> to NULL legacy PIC and nr_legacy_irqs() starts to return 0 but we already
>> have 16 descs allocated.
>>
>> Solve the issue by separating i8259 probe from init and calling it in
>> arch_probe_nr_irqs() before we actually use nr_legacy_irqs() information.
>>
>> Fixes: d32932d02e18 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain interfaces")
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> Cc: Jiang Liu <jiang.liu@linux.intel.com>
>> Cc: K. Y. Srinivasan <kys@microsoft.com>
>> Link: http://lkml.kernel.org/r/1446543614-3621-1-git-send-email-vkuznets@redhat.com
>> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>>
>> ---
>>  arch/x86/include/asm/i8259.h  |    1 +
>>  arch/x86/kernel/apic/vector.c |    6 +++++-
>>  arch/x86/kernel/i8259.c       |   29 +++++++++++++++++++++--------
>>  3 files changed, 27 insertions(+), 9 deletions(-)
>>
>> --- a/arch/x86/include/asm/i8259.h
>> +++ b/arch/x86/include/asm/i8259.h
>> @@ -60,6 +60,7 @@ struct legacy_pic {
>>       void (*mask_all)(void);
>>       void (*restore_mask)(void);
>>       void (*init)(int auto_eoi);
>> +     int (*probe)(void);
>>       int (*irq_pending)(unsigned int irq);
>>       void (*make_irq)(unsigned int irq);
>>  };
>> --- a/arch/x86/kernel/apic/vector.c
>> +++ b/arch/x86/kernel/apic/vector.c
>> @@ -361,7 +361,11 @@ int __init arch_probe_nr_irqs(void)
>>       if (nr < nr_irqs)
>>               nr_irqs = nr;
>>
>> -     return nr_legacy_irqs();
>> +     /*
>> +      * We don't know if PIC is present at this point so we need to do
>> +      * probe() to get the right number of legacy IRQs.
>> +      */
>> +     return legacy_pic->probe();
>>  }
>>
>>  #ifdef       CONFIG_X86_IO_APIC
>> --- a/arch/x86/kernel/i8259.c
>> +++ b/arch/x86/kernel/i8259.c
>> @@ -295,16 +295,11 @@ static void unmask_8259A(void)
>>       raw_spin_unlock_irqrestore(&i8259A_lock, flags);
>>  }
>>
>> -static void init_8259A(int auto_eoi)
>> +static int probe_8259A(void)
>>  {
>>       unsigned long flags;
>>       unsigned char probe_val = ~(1 << PIC_CASCADE_IR);
>>       unsigned char new_val;
>> -
>> -     i8259A_auto_eoi = auto_eoi;
>> -
>> -     raw_spin_lock_irqsave(&i8259A_lock, flags);
>> -
>>       /*
>>        * Check to see if we have a PIC.
>>        * Mask all except the cascade and read
>> @@ -312,16 +307,28 @@ static void init_8259A(int auto_eoi)
>>        * have a PIC, we will read 0xff as opposed to the
>>        * value we wrote.
>>        */
>> +     raw_spin_lock_irqsave(&i8259A_lock, flags);
>> +
>>       outb(0xff, PIC_SLAVE_IMR);      /* mask all of 8259A-2 */
>>       outb(probe_val, PIC_MASTER_IMR);
>>       new_val = inb(PIC_MASTER_IMR);
>>       if (new_val != probe_val) {
>>               printk(KERN_INFO "Using NULL legacy PIC\n");
>>               legacy_pic = &null_legacy_pic;
>> -             raw_spin_unlock_irqrestore(&i8259A_lock, flags);
>> -             return;
>>       }
>>
>> +     raw_spin_unlock_irqrestore(&i8259A_lock, flags);
>> +     return nr_legacy_irqs();
>> +}
>> +
>> +static void init_8259A(int auto_eoi)
>> +{
>> +     unsigned long flags;
>> +
>> +     i8259A_auto_eoi = auto_eoi;
>> +
>> +     raw_spin_lock_irqsave(&i8259A_lock, flags);
>> +
>>       outb(0xff, PIC_MASTER_IMR);     /* mask all of 8259A-1 */
>>
>>       /*
>> @@ -379,6 +386,10 @@ static int legacy_pic_irq_pending_noop(u
>>  {
>>       return 0;
>>  }
>> +static int legacy_pic_probe(void)
>> +{
>> +     return 0;
>> +}
>>
>>  struct legacy_pic null_legacy_pic = {
>>       .nr_legacy_irqs = 0,
>> @@ -388,6 +399,7 @@ struct legacy_pic null_legacy_pic = {
>>       .mask_all = legacy_pic_noop,
>>       .restore_mask = legacy_pic_noop,
>>       .init = legacy_pic_int_noop,
>> +     .probe = legacy_pic_probe,
>>       .irq_pending = legacy_pic_irq_pending_noop,
>>       .make_irq = legacy_pic_uint_noop,
>>  };
>> @@ -400,6 +412,7 @@ struct legacy_pic default_legacy_pic = {
>>       .mask_all = mask_8259A,
>>       .restore_mask = unmask_8259A,
>>       .init = init_8259A,
>> +     .probe = probe_8259A,
>>       .irq_pending = i8259A_irq_pending,
>>       .make_irq = make_8259A_irq,
>>  };
>>
>> Patches currently in stable-queue which might be from vkuznets@redhat.com are
>>
>> queue-4.3/x86-irq-probe-for-pic-presence-before-allocating-descs-for-legacy-irqs.patch

Re: Patch "x86/irq: Probe for PIC presence before allocating descs for legacy IRQs" has been added to the 4.3-stable tree

[Greg KH]

On Mon, Dec 07, 2015 at 01:54:35PM +0100, Vitaly Kuznetsov wrote:
> <gregkh@linuxfoundation.org> writes:
> 
> > This is a note to let you know that I've just added the patch titled
> >
> >     x86/irq: Probe for PIC presence before allocating descs for legacy IRQs
> >
> > to the 4.3-stable tree which can be found at:
> >     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> >
> > The filename of the patch is:
> >      x86-irq-probe-for-pic-presence-before-allocating-descs-for-legacy-irqs.patch
> > and it can be found in the queue-4.3 subdirectory.
> >
> > If you, or anyone else, feels it should not be added to the stable tree,
> > please let <stable@vger.kernel.org> know about it.
> 
> This commit is known for breaking Xen PV guests, the breakage is fixed
> with the following:
> 
> commit b4ff8389ed14b849354b59ce9b360bdefcdbf99c
> Author: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> Date:   Fri Nov 20 11:25:04 2015 -0500
> 
>     xen/events: Always allocate legacy interrupts on PV guests
> 
> I suggest we include this commit as well. Same for 4.2-stable tree.

Thanks, now applied.

greg k-h

Re: [Xen-devel] Patch "x86/irq: Probe for PIC presence before allocating descs for legacy IRQs" has been added to the 4.3-stable tree

[Greg KH]

On Mon, Dec 07, 2015 at 02:17:30PM +0100, Sander Eikelenboom wrote:
> 
> Monday, December 7, 2015, 1:54:35 PM, you wrote:
> 
> > <gregkh@linuxfoundation.org> writes:
> 
> >> This is a note to let you know that I've just added the patch titled
> >>
> >>     x86/irq: Probe for PIC presence before allocating descs for legacy IRQs
> >>
> >> to the 4.3-stable tree which can be found at:
> >>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> >>
> >> The filename of the patch is:
> >>      x86-irq-probe-for-pic-presence-before-allocating-descs-for-legacy-irqs.patch
> >> and it can be found in the queue-4.3 subdirectory.
> >>
> >> If you, or anyone else, feels it should not be added to the stable tree,
> >> please let <stable@vger.kernel.org> know about it.
> 
> > This commit is known for breaking Xen PV guests, the breakage is fixed
> > with the following:
> 
> > commit b4ff8389ed14b849354b59ce9b360bdefcdbf99c
> > Author: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> > Date:   Fri Nov 20 11:25:04 2015 -0500
> 
> >     xen/events: Always allocate legacy interrupts on PV guests
> 
> > I suggest we include this commit as well. Same for 4.2-stable tree.
> 
> Which in turn causes the problem described in:
> "Xen-devel] [PATCHv1] x86: rtc_cmos platform device requires legacy irqs"
> http://lkml.iu.edu/hypermail/linux/kernel/1512.0/02430.html
> 
> for which a patch is still pending a discussion about the right way to fix it.

When a patch to resolve it gets into Linus's tree, please tell
stable@vger.kernel.org about it.

thanks,

greg k-h