[v5 0/3] prerequisite changes for VT-d posted-interrupts

[v5 0/3] prerequisite changes for VT-d posted-interrupts

[Feng Wu]

VT-d Posted-Interrupts is an enhancement to CPU side Posted-Interrupt.
With VT-d Posted-Interrupts enabled, external interrupts from
direct-assigned devices can be delivered to guests without VMM
intervention when guest is running in non-root mode.

You can find the VT-d Posted-Interrtups Spec. in the following URL:
http://www.intel.com/content/www/us/en/intelligent-systems/intel-technology/vt-directed-io-spec.html

This series implement some prerequisite parts for VT-d posted-interrupts. It was part of
http://thread.gmane.org/gmane.linux.kernel.iommu/7708. To make things clear, I will divide
the whole series which contain multiple components into three parts:
- prerequisite changes (included in this series)
- IOMMU part (v4 was reviewed, some comments need to be addressed)
- KVM and VFIO parts (will send out this part once the first two parts are accepted)

This series is rebased on the x86-apic branch of tip tree.

v4 --> v5:
- Move the declaration of "irq_chip_set_vcpu_affinity_parent()" to [1/3].
- Use the accessor to get "struct irq_data", "struct irq_chip".
- Use "irq_get_desc_lock()" instead of "irq_to_desc()".
- Declare "wakeup_handler_callback" in "asm/irq.h".
- Use entering_ack_irq()/exiting_irq() in smp_kvm_posted_intr_wakeup_ipi().

Feng Wu (2):
  x86, irq: Implement irq_set_vcpu_affinity for pci_msi_ir_controller
  x86, irq: Define a global vector for VT-d Posted-Interrupts

Jiang Liu (1):
  genirq: Introduce irq_set_vcpu_affinity() to target an interrupt to a
    VCPU

 arch/x86/include/asm/entry_arch.h  |  2 ++
 arch/x86/include/asm/hardirq.h     |  1 +
 arch/x86/include/asm/hw_irq.h      |  2 ++
 arch/x86/include/asm/irq.h         |  4 ++++
 arch/x86/include/asm/irq_vectors.h |  1 +
 arch/x86/kernel/apic/msi.c         |  1 +
 arch/x86/kernel/entry_64.S         |  2 ++
 arch/x86/kernel/irq.c              | 23 +++++++++++++++++++++++
 arch/x86/kernel/irqinit.c          |  2 ++
 include/linux/irq.h                |  6 ++++++
 kernel/irq/chip.c                  | 14 ++++++++++++++
 kernel/irq/manage.c                | 21 +++++++++++++++++++++
 12 files changed, 79 insertions(+)

-- 
2.1.0

[v5 1/3] genirq: Introduce irq_set_vcpu_affinity() to target an interrupt to a VCPU

[Feng Wu]

From: Jiang Liu <jiang.liu@linux.intel.com>

With Posted-Interrupts support in Intel CPU and IOMMU, an external
interrupt from assigned-devices could be directly delivered to a
virtual CPU in a virtual machine. Instead of hacking KVM and Intel
IOMMU drivers, we propose a platform independent interface to target
an interrupt to a specific virtual CPU in a virtual machine, or set
virtual CPU affinity for an interrupt.

By adopting this new interface and the hierarchy irqdomain, we could
easily support posted-interrupts on Intel platforms, and also provide
flexible enough interfaces for other platforms to support similar
features.

Here is the usage scenario for this interface:
Guest update MSI/MSI-X interrupt configuration
        -->QEMU and KVM handle this
        -->KVM call this interface (passing posted interrupts descriptor
           and guest vector)
        -->irq core will transfer the control to IOMMU
        -->IOMMU will do the real work of updating IRTE (IRTE has new
           format for VT-d Posted-Interrupts)

Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>
Signed-off-by: Feng Wu <feng.wu@intel.com>
---
 include/linux/irq.h |  6 ++++++
 kernel/irq/chip.c   | 14 ++++++++++++++
 kernel/irq/manage.c | 21 +++++++++++++++++++++
 3 files changed, 41 insertions(+)

diff --git a/include/linux/irq.h b/include/linux/irq.h
index 62c6901..cb688fb 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -327,6 +327,7 @@ static inline irq_hw_number_t irqd_to_hwirq(struct irq_data *d)
  * @irq_write_msi_msg:	optional to write message content for MSI
  * @irq_get_irqchip_state:	return the internal state of an interrupt
  * @irq_set_irqchip_state:	set the internal state of a interrupt
+ * @irq_set_vcpu_affinity:	optional to target a vCPU in a virtual machine
  * @flags:		chip specific flags
  */
 struct irq_chip {
@@ -369,6 +370,8 @@ struct irq_chip {
 	int		(*irq_get_irqchip_state)(struct irq_data *data, enum irqchip_irq_state which, bool *state);
 	int		(*irq_set_irqchip_state)(struct irq_data *data, enum irqchip_irq_state which, bool state);
 
+	int		(*irq_set_vcpu_affinity)(struct irq_data *data, void *vcpu_info);
+
 	unsigned long	flags;
 };
 
@@ -422,6 +425,7 @@ extern void irq_cpu_online(void);
 extern void irq_cpu_offline(void);
 extern int irq_set_affinity_locked(struct irq_data *data,
 				   const struct cpumask *cpumask, bool force);
+extern int irq_set_vcpu_affinity(unsigned int irq, void *vcpu_info);
 
 #if defined(CONFIG_SMP) && defined(CONFIG_GENERIC_PENDING_IRQ)
 void irq_move_irq(struct irq_data *data);
@@ -467,6 +471,8 @@ extern int irq_chip_set_affinity_parent(struct irq_data *data,
 					const struct cpumask *dest,
 					bool force);
 extern int irq_chip_set_wake_parent(struct irq_data *data, unsigned int on);
+extern int irq_chip_set_vcpu_affinity_parent(struct irq_data *data,
+					     void *vcpu_info);
 #endif
 
 /* Handling of unhandled and spurious interrupts: */
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index eb9a4ea..55016b2 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -950,6 +950,20 @@ int irq_chip_retrigger_hierarchy(struct irq_data *data)
 }
 
 /**
+ * irq_chip_set_vcpu_affinity_parent - Set vcpu affinity on the parent interrupt
+ * @data:	Pointer to interrupt specific data
+ * @dest:	The vcpu affinity information
+ */
+int irq_chip_set_vcpu_affinity_parent(struct irq_data *data, void *vcpu_info)
+{
+	data = data->parent_data;
+	if (data->chip->irq_set_vcpu_affinity)
+		return data->chip->irq_set_vcpu_affinity(data, vcpu_info);
+
+	return -ENOSYS;
+}
+
+/**
  * irq_chip_set_wake_parent - Set/reset wake-up on the parent interrupt
  * @data:	Pointer to interrupt specific data
  * @on:		Whether to set or reset the wake-up capability of this irq
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index e68932b..7167825 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -256,6 +256,27 @@ int irq_set_affinity_hint(unsigned int irq, const struct cpumask *m)
 }
 EXPORT_SYMBOL_GPL(irq_set_affinity_hint);
 
+int irq_set_vcpu_affinity(unsigned int irq, void *vcpu_info)
+{
+	unsigned long flags;
+	struct irq_desc *desc = irq_get_desc_lock(irq, &flags, 0);
+	struct irq_data *data;
+	struct irq_chip *chip;
+	int ret = -ENOSYS;
+
+	if (!desc)
+		return -EINVAL;
+
+	data = irq_desc_get_irq_data(desc);
+	chip = irq_data_get_irq_chip(data);
+	if (chip && chip->irq_set_vcpu_affinity)
+		ret = chip->irq_set_vcpu_affinity(data, vcpu_info);
+	irq_put_desc_unlock(desc, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(irq_set_vcpu_affinity);
+
 static void irq_affinity_notify(struct work_struct *work)
 {
 	struct irq_affinity_notify *notify =
-- 
2.1.0

[v5 2/3] x86, irq: Implement irq_set_vcpu_affinity for pci_msi_ir_controller

[Feng Wu]

Implement irq_set_vcpu_affinity for pci_msi_ir_controller.

Signed-off-by: Feng Wu <feng.wu@intel.com>
Reviewed-by: Jiang Liu <jiang.liu@linux.intel.com>
---
 arch/x86/kernel/apic/msi.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/apic/msi.c b/arch/x86/kernel/apic/msi.c
index 58fde66..d2d95e2 100644
--- a/arch/x86/kernel/apic/msi.c
+++ b/arch/x86/kernel/apic/msi.c
@@ -152,6 +152,7 @@ static struct irq_chip pci_msi_ir_controller = {
 	.irq_mask		= pci_msi_mask_irq,
 	.irq_ack		= irq_chip_ack_parent,
 	.irq_retrigger		= irq_chip_retrigger_hierarchy,
+	.irq_set_vcpu_affinity	= irq_chip_set_vcpu_affinity_parent,
 	.flags			= IRQCHIP_SKIP_SET_WAKE,
 };
 
-- 
2.1.0

[v5 3/3] x86, irq: Define a global vector for VT-d Posted-Interrupts

[Feng Wu]

Currently, we use a global vector as the Posted-Interrupts
Notification Event for all the vCPUs in the system. We need
to introduce another global vector for VT-d Posted-Interrtups,
which will be used to wakeup the sleep vCPU when an external
interrupt from a direct-assigned device happens for that vCPU.

Signed-off-by: Feng Wu <feng.wu@intel.com>
Suggested-by: Yang Zhang <yang.z.zhang@intel.com>
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
---
 arch/x86/include/asm/entry_arch.h  |  2 ++
 arch/x86/include/asm/hardirq.h     |  1 +
 arch/x86/include/asm/hw_irq.h      |  2 ++
 arch/x86/include/asm/irq.h         |  4 ++++
 arch/x86/include/asm/irq_vectors.h |  1 +
 arch/x86/kernel/entry_64.S         |  2 ++
 arch/x86/kernel/irq.c              | 23 +++++++++++++++++++++++
 arch/x86/kernel/irqinit.c          |  2 ++
 8 files changed, 37 insertions(+)

diff --git a/arch/x86/include/asm/entry_arch.h b/arch/x86/include/asm/entry_arch.h
index dc5fa66..27ca0af 100644
--- a/arch/x86/include/asm/entry_arch.h
+++ b/arch/x86/include/asm/entry_arch.h
@@ -23,6 +23,8 @@ BUILD_INTERRUPT(x86_platform_ipi, X86_PLATFORM_IPI_VECTOR)
 #ifdef CONFIG_HAVE_KVM
 BUILD_INTERRUPT3(kvm_posted_intr_ipi, POSTED_INTR_VECTOR,
 		 smp_kvm_posted_intr_ipi)
+BUILD_INTERRUPT3(kvm_posted_intr_wakeup_ipi, POSTED_INTR_WAKEUP_VECTOR,
+		 smp_kvm_posted_intr_wakeup_ipi)
 #endif
 
 /*
diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
index 0f5fb6b..9866065 100644
--- a/arch/x86/include/asm/hardirq.h
+++ b/arch/x86/include/asm/hardirq.h
@@ -14,6 +14,7 @@ typedef struct {
 #endif
 #ifdef CONFIG_HAVE_KVM
 	unsigned int kvm_posted_intr_ipis;
+	unsigned int kvm_posted_intr_wakeup_ipis;
 #endif
 	unsigned int x86_platform_ipis;	/* arch dependent */
 	unsigned int apic_perf_irqs;
diff --git a/arch/x86/include/asm/hw_irq.h b/arch/x86/include/asm/hw_irq.h
index 1f88e71..6ffc847 100644
--- a/arch/x86/include/asm/hw_irq.h
+++ b/arch/x86/include/asm/hw_irq.h
@@ -29,6 +29,7 @@
 extern asmlinkage void apic_timer_interrupt(void);
 extern asmlinkage void x86_platform_ipi(void);
 extern asmlinkage void kvm_posted_intr_ipi(void);
+extern asmlinkage void kvm_posted_intr_wakeup_ipi(void);
 extern asmlinkage void error_interrupt(void);
 extern asmlinkage void irq_work_interrupt(void);
 
@@ -92,6 +93,7 @@ extern void trace_call_function_single_interrupt(void);
 #define trace_irq_move_cleanup_interrupt  irq_move_cleanup_interrupt
 #define trace_reboot_interrupt  reboot_interrupt
 #define trace_kvm_posted_intr_ipi kvm_posted_intr_ipi
+#define trace_kvm_posted_intr_wakeup_ipi kvm_posted_intr_wakeup_ipi
 #endif /* CONFIG_TRACING */
 
 #ifdef	CONFIG_X86_LOCAL_APIC
diff --git a/arch/x86/include/asm/irq.h b/arch/x86/include/asm/irq.h
index a80cbb8..16bfe4e 100644
--- a/arch/x86/include/asm/irq.h
+++ b/arch/x86/include/asm/irq.h
@@ -30,6 +30,10 @@ extern void fixup_irqs(void);
 extern void irq_force_complete_move(int);
 #endif
 
+#ifdef CONFIG_HAVE_KVM
+	extern void (*wakeup_handler_callback)(void);
+#endif
+
 extern void (*x86_platform_ipi_callback)(void);
 extern void native_init_IRQ(void);
 extern bool handle_irq(unsigned irq, struct pt_regs *regs);
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index b26cb12..dca94f2 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -105,6 +105,7 @@
 /* Vector for KVM to deliver posted interrupt IPI */
 #ifdef CONFIG_HAVE_KVM
 #define POSTED_INTR_VECTOR		0xf2
+#define POSTED_INTR_WAKEUP_VECTOR	0xf1
 #endif
 
 /*
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index c7b2384..177feec 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -919,6 +919,8 @@ apicinterrupt X86_PLATFORM_IPI_VECTOR \
 #ifdef CONFIG_HAVE_KVM
 apicinterrupt3 POSTED_INTR_VECTOR \
 	kvm_posted_intr_ipi smp_kvm_posted_intr_ipi
+apicinterrupt3 POSTED_INTR_WAKEUP_VECTOR \
+	kvm_posted_intr_wakeup_ipi smp_kvm_posted_intr_wakeup_ipi
 #endif
 
 #ifdef CONFIG_X86_MCE_THRESHOLD
diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index e5952c2..87620bf 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -237,6 +237,9 @@ __visible void smp_x86_platform_ipi(struct pt_regs *regs)
 }
 
 #ifdef CONFIG_HAVE_KVM
+void (*wakeup_handler_callback)(void);
+EXPORT_SYMBOL_GPL(wakeup_handler_callback);
+
 /*
  * Handler for POSTED_INTERRUPT_VECTOR.
  */
@@ -256,6 +259,26 @@ __visible void smp_kvm_posted_intr_ipi(struct pt_regs *regs)
 
 	set_irq_regs(old_regs);
 }
+
+/*
+ * Handler for POSTED_INTERRUPT_WAKEUP_VECTOR.
+ */
+__visible void smp_kvm_posted_intr_wakeup_ipi(struct pt_regs *regs)
+{
+	struct pt_regs *old_regs = set_irq_regs(regs);
+
+	entering_ack_irq();
+
+	inc_irq_stat(kvm_posted_intr_wakeup_ipis);
+
+	if (wakeup_handler_callback)
+		wakeup_handler_callback();
+
+	exiting_irq();
+
+	set_irq_regs(old_regs);
+}
+
 #endif
 
 __visible void smp_trace_x86_platform_ipi(struct pt_regs *regs)
diff --git a/arch/x86/kernel/irqinit.c b/arch/x86/kernel/irqinit.c
index cd10a64..895941d 100644
--- a/arch/x86/kernel/irqinit.c
+++ b/arch/x86/kernel/irqinit.c
@@ -144,6 +144,8 @@ static void __init apic_intr_init(void)
 #ifdef CONFIG_HAVE_KVM
 	/* IPI for KVM to deliver posted interrupt */
 	alloc_intr_gate(POSTED_INTR_VECTOR, kvm_posted_intr_ipi);
+	/* IPI for KVM to deliver interrupt to wake up tasks */
+	alloc_intr_gate(POSTED_INTR_WAKEUP_VECTOR, kvm_posted_intr_wakeup_ipi);
 #endif
 
 	/* IPI vectors for APIC spurious and error interrupts */
-- 
2.1.0

Re: [v5 3/3] x86, irq: Define a global vector for VT-d Posted-Interrupts

[Thomas Gleixner]

On Mon, 18 May 2015, Feng Wu wrote:
> diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
> index 0f5fb6b..9866065 100644
> --- a/arch/x86/include/asm/hardirq.h
> +++ b/arch/x86/include/asm/hardirq.h
> @@ -14,6 +14,7 @@ typedef struct {
>  #endif
>  #ifdef CONFIG_HAVE_KVM
>  	unsigned int kvm_posted_intr_ipis;
> +	unsigned int kvm_posted_intr_wakeup_ipis;

So now we have another IPI with statistics and nothing which makes it
accessible. kvm_posted_intr_ipis lacks a printout in
arch_show_interrupts() as well.

>  #ifdef CONFIG_HAVE_KVM
> +void (*wakeup_handler_callback)(void);
> +EXPORT_SYMBOL_GPL(wakeup_handler_callback);
> +

The naming sucks. Which wakeup?

As this is kvm specific, it should have a kvm_ prefix. And it should
tell what it actually does: 
     
     kvm_posted_intr_wakeup_handler

Hmm?

>  /*
>   * Handler for POSTED_INTERRUPT_VECTOR.
>   */
> @@ -256,6 +259,26 @@ __visible void smp_kvm_posted_intr_ipi(struct pt_regs *regs)
>  
>  	set_irq_regs(old_regs);
>  }
> +
> +/*
> + * Handler for POSTED_INTERRUPT_WAKEUP_VECTOR.
> + */
> +__visible void smp_kvm_posted_intr_wakeup_ipi(struct pt_regs *regs)
> +{
> +	struct pt_regs *old_regs = set_irq_regs(regs);
> +
> +	entering_ack_irq();
> +
> +	inc_irq_stat(kvm_posted_intr_wakeup_ipis);
> +
> +	if (wakeup_handler_callback)
> +		wakeup_handler_callback();

Why do we need a conditional here?

staic void dummy_handler(void) { }
static void *kvm_posted_intr_wakeup_handler = dummy_handler;

void kvm_set_posted_intr_wakeup_handler(void (*handler)(void))
{
	if (handler)
		kvm_posted_intr_wakeup_handler = handler;
	else
		kvm_posted_intr_wakeup_handler = dummy_handler;
}

avoids the conditional in the exception handler....

Thanks,

	tglx

RE: [v5 3/3] x86, irq: Define a global vector for VT-d Posted-Interrupts

[Wu, Feng]

> -----Original Message-----
> From: Thomas Gleixner [mailto:tglx@linutronix.de]
> Sent: Monday, May 18, 2015 10:18 PM
> To: Wu, Feng
> Cc: mingo@redhat.com; hpa@zytor.com; linux-kernel@vger.kernel.org;
> jiang.liu@linux.intel.com
> Subject: Re: [v5 3/3] x86, irq: Define a global vector for VT-d Posted-Interrupts
> 
> On Mon, 18 May 2015, Feng Wu wrote:
> > diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h
> > index 0f5fb6b..9866065 100644
> > --- a/arch/x86/include/asm/hardirq.h
> > +++ b/arch/x86/include/asm/hardirq.h
> > @@ -14,6 +14,7 @@ typedef struct {
> >  #endif
> >  #ifdef CONFIG_HAVE_KVM
> >  	unsigned int kvm_posted_intr_ipis;
> > +	unsigned int kvm_posted_intr_wakeup_ipis;
> 
> So now we have another IPI with statistics and nothing which makes it
> accessible. kvm_posted_intr_ipis lacks a printout in
> arch_show_interrupts() as well.
> 

I will add the printouts for these two IPIs.

> >  #ifdef CONFIG_HAVE_KVM
> > +void (*wakeup_handler_callback)(void);
> > +EXPORT_SYMBOL_GPL(wakeup_handler_callback);
> > +
> 
> The naming sucks. Which wakeup?
> 
> As this is kvm specific, it should have a kvm_ prefix. And it should
> tell what it actually does:
> 
>      kvm_posted_intr_wakeup_handler
> 
> Hmm?

Good suggestion!

> 
> >  /*
> >   * Handler for POSTED_INTERRUPT_VECTOR.
> >   */
> > @@ -256,6 +259,26 @@ __visible void smp_kvm_posted_intr_ipi(struct
> pt_regs *regs)
> >
> >  	set_irq_regs(old_regs);
> >  }
> > +
> > +/*
> > + * Handler for POSTED_INTERRUPT_WAKEUP_VECTOR.
> > + */
> > +__visible void smp_kvm_posted_intr_wakeup_ipi(struct pt_regs *regs)
> > +{
> > +	struct pt_regs *old_regs = set_irq_regs(regs);
> > +
> > +	entering_ack_irq();
> > +
> > +	inc_irq_stat(kvm_posted_intr_wakeup_ipis);
> > +
> > +	if (wakeup_handler_callback)
> > +		wakeup_handler_callback();
> 
> Why do we need a conditional here?
> 
> staic void dummy_handler(void) { }
> static void *kvm_posted_intr_wakeup_handler = dummy_handler;
> 
> void kvm_set_posted_intr_wakeup_handler(void (*handler)(void))
> {
> 	if (handler)
> 		kvm_posted_intr_wakeup_handler = handler;
> 	else
> 		kvm_posted_intr_wakeup_handler = dummy_handler;
> }
> 
> avoids the conditional in the exception handler....

Got it. Conditional branch in a critical path is really a bad thing...

Thanks,
Feng

> 
> Thanks,
> 
> 	tglx