Re: [PATCH] IRQ: manually EOI migrating line interrupts

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 30/08/11 15:17, Andrew Cooper wrote:
> When migrating IO-APIC line level interrupts between PCPUs, the
> migration code rewrites the IO-APIC entry to point to the new
> CPU/Vector before EOI'ing it.
>
> The EOI process says that EOI'ing the Local APIC will cause a
> broadcast with the vector number, which the IO-APIC must listen to to
> clear the IRR and Status bits.
>
> In the case of migrating, the IO-APIC has already been
> reprogrammed so the EOI broadcast with the old vector fails to match
> the new vector, leaving the IO-APIC with an outstanding vector,
> preventing any more use of that line interrupt.  This causes a lockup
> especially when your root device is using PCI INTA (megaraid_sas
> driver *ehem*)
>
> However, the problem is mostly hidden because send_cleanup_vector()
> causes a cleanup of all moving vectors on the current PCPU in such a
> way which does not cause the problem, and if the problem has occured,
> the writes it makes to the IO-APIC clears the IRR and Status bits
> which unlocks the problem.
>
>
> This fix is distinctly a temporary hack, waiting on a cleanup of the
> irq code.  It checks for the edge case where we have moved the irq,
> and manually EOI's the old vector with the IO-APIC which correctly
> clears the IRR and Status bits.  Also, it protects the code which
> updates irq_cfg by disabling interrupts.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

P.S.

Because this fix actually works, it means that EOI'ing the IO-APIC is
keyed only on vector, and not the target CPU.  As a result, having two
different interrupts in the IO-APIC with the same vector will result in
problems when trying to EOI one of them.

I will address this problem as well in my IRQ cleanup, as I cant see any
checks for it currently.

~Andrew

> diff -r 227130622561 -r a95fd5d03c20 xen/arch/x86/hpet.c
> --- a/xen/arch/x86/hpet.c	Thu Aug 25 12:03:14 2011 +0100
> +++ b/xen/arch/x86/hpet.c	Tue Aug 30 15:15:56 2011 +0100
> @@ -301,7 +301,7 @@ static void hpet_msi_ack(unsigned int ir
>      ack_APIC_irq();
>  }
>  
> -static void hpet_msi_end(unsigned int irq)
> +static void hpet_msi_end(unsigned int irq, u8 vector)
>  {
>  }
>  
> diff -r 227130622561 -r a95fd5d03c20 xen/arch/x86/i8259.c
> --- a/xen/arch/x86/i8259.c	Thu Aug 25 12:03:14 2011 +0100
> +++ b/xen/arch/x86/i8259.c	Tue Aug 30 15:15:56 2011 +0100
> @@ -93,7 +93,7 @@ static unsigned int startup_8259A_irq(un
>      return 0; /* never anything pending */
>  }
>  
> -static void end_8259A_irq(unsigned int irq)
> +static void end_8259A_irq(unsigned int irq, u8 vector)
>  {
>      if (!(irq_desc[irq].status & (IRQ_DISABLED|IRQ_INPROGRESS)))
>          enable_8259A_irq(irq);
> diff -r 227130622561 -r a95fd5d03c20 xen/arch/x86/io_apic.c
> --- a/xen/arch/x86/io_apic.c	Thu Aug 25 12:03:14 2011 +0100
> +++ b/xen/arch/x86/io_apic.c	Tue Aug 30 15:15:56 2011 +0100
> @@ -1690,7 +1690,7 @@ static void mask_and_ack_level_ioapic_ir
>      }
>  }
>  
> -static void end_level_ioapic_irq (unsigned int irq)
> +static void end_level_ioapic_irq (unsigned int irq, u8 vector)
>  {
>      unsigned long v;
>      int i;
> @@ -1739,6 +1739,14 @@ static void end_level_ioapic_irq (unsign
>   */
>      i = IO_APIC_VECTOR(irq);
>  
> +    /* Manually EOI the old vector if we are moving to the new */
> +    if ( vector && i != vector )
> +    {
> +        int ioapic;
> +        for (ioapic = 0; ioapic < nr_ioapics; ioapic++)
> +            io_apic_eoi(ioapic, i);
> +    }
> +
>      v = apic_read(APIC_TMR + ((i & ~0x1f) >> 1));
>  
>      ack_APIC_irq();
> @@ -1762,7 +1770,10 @@ static void disable_edge_ioapic_irq(unsi
>  {
>  }
>  
> -#define end_edge_ioapic_irq disable_edge_ioapic_irq
> +static void end_edge_ioapic_irq(unsigned int irq, u8 vector)
> +{
> +}
> +
>  
>  /*
>   * Level and edge triggered IO-APIC interrupts need different handling,
> @@ -1811,7 +1822,7 @@ static void ack_msi_irq(unsigned int irq
>          ack_APIC_irq(); /* ACKTYPE_NONE */
>  }
>  
> -static void end_msi_irq(unsigned int irq)
> +static void end_msi_irq(unsigned int irq, u8 vector)
>  {
>      if ( !msi_maskable_irq(irq_desc[irq].msi_desc) )
>          ack_APIC_irq(); /* ACKTYPE_EOI */
> diff -r 227130622561 -r a95fd5d03c20 xen/arch/x86/irq.c
> --- a/xen/arch/x86/irq.c	Thu Aug 25 12:03:14 2011 +0100
> +++ b/xen/arch/x86/irq.c	Tue Aug 30 15:15:56 2011 +0100
> @@ -345,6 +345,7 @@ static void __do_IRQ_guest(int vector);
>  void no_action(int cpl, void *dev_id, struct cpu_user_regs *regs) { }
>  
>  static void enable_none(unsigned int vector) { }
> +static void end_none(unsigned int irq, u8 vector) { }
>  static unsigned int startup_none(unsigned int vector) { return 0; }
>  static void disable_none(unsigned int vector) { }
>  static void ack_none(unsigned int irq)
> @@ -353,7 +354,6 @@ static void ack_none(unsigned int irq)
>  }
>  
>  #define shutdown_none   disable_none
> -#define end_none        enable_none
>  
>  hw_irq_controller no_irq_type = {
>      "none",
> @@ -381,6 +381,7 @@ int __assign_irq_vector(int irq, struct 
>      static int current_vector = FIRST_DYNAMIC_VECTOR, current_offset = 0;
>      unsigned int old_vector;
>      int cpu, err;
> +    unsigned long flags;
>      cpumask_t tmp_mask;
>  
>      old_vector = irq_to_vector(irq);
> @@ -431,6 +432,7 @@ next:
>          /* Found one! */
>          current_vector = vector;
>          current_offset = offset;
> +        local_irq_save(flags);
>          if (old_vector) {
>              cfg->move_in_progress = 1;
>              cpus_copy(cfg->old_cpu_mask, cfg->cpu_mask);
> @@ -450,6 +452,7 @@ next:
>              if (IO_APIC_IRQ(irq))
>                      irq_vector[irq] = vector;
>          err = 0;
> +        local_irq_restore(flags);
>          break;
>      }
>      return err;
> @@ -657,7 +660,7 @@ asmlinkage void do_IRQ(struct cpu_user_r
>      desc->status &= ~IRQ_INPROGRESS;
>  
>   out:
> -    desc->handler->end(irq);
> +    desc->handler->end(irq, regs->entry_vector);
>   out_no_end:
>      spin_unlock(&desc->lock);
>      irq_exit();
> @@ -857,7 +860,7 @@ static void irq_guest_eoi_timer_fn(void 
>      switch ( action->ack_type )
>      {
>      case ACKTYPE_UNMASK:
> -        desc->handler->end(irq);
> +        desc->handler->end(irq, 0);
>          break;
>      case ACKTYPE_EOI:
>          cpu_eoi_map = action->cpu_eoi_map;
> @@ -885,7 +888,7 @@ static void __do_IRQ_guest(int irq)
>          /* An interrupt may slip through while freeing an ACKTYPE_EOI irq. */
>          ASSERT(action->ack_type == ACKTYPE_EOI);
>          ASSERT(desc->status & IRQ_DISABLED);
> -        desc->handler->end(irq);
> +        desc->handler->end(irq, vector);
>          return;
>      }
>  
> @@ -1099,7 +1102,7 @@ static void flush_ready_eoi(void)
>          ASSERT(irq > 0);
>          desc = irq_to_desc(irq);
>          spin_lock(&desc->lock);
> -        desc->handler->end(irq);
> +        desc->handler->end(irq, peoi[sp].vector);
>          spin_unlock(&desc->lock);
>      }
>  
> @@ -1177,7 +1180,7 @@ void desc_guest_eoi(struct irq_desc *des
>      if ( action->ack_type == ACKTYPE_UNMASK )
>      {
>          ASSERT(cpus_empty(action->cpu_eoi_map));
> -        desc->handler->end(irq);
> +        desc->handler->end(irq, 0);
>          spin_unlock_irq(&desc->lock);
>          return;
>      }
> @@ -1431,7 +1434,7 @@ static irq_guest_action_t *__pirq_guest_
>      case ACKTYPE_UNMASK:
>          if ( test_and_clear_bool(pirq->masked) &&
>               (--action->in_flight == 0) )
> -            desc->handler->end(irq);
> +            desc->handler->end(irq, 0);
>          break;
>      case ACKTYPE_EOI:
>          /* NB. If #guests == 0 then we clear the eoi_map later on. */
> diff -r 227130622561 -r a95fd5d03c20 xen/drivers/passthrough/amd/iommu_init.c
> --- a/xen/drivers/passthrough/amd/iommu_init.c	Thu Aug 25 12:03:14 2011 +0100
> +++ b/xen/drivers/passthrough/amd/iommu_init.c	Tue Aug 30 15:15:56 2011 +0100
> @@ -441,7 +441,7 @@ static unsigned int iommu_msi_startup(un
>      return 0;
>  }
>  
> -static void iommu_msi_end(unsigned int irq)
> +static void iommu_msi_end(unsigned int irq, u8 vector)
>  {
>      iommu_msi_unmask(irq);
>      ack_APIC_irq();
> diff -r 227130622561 -r a95fd5d03c20 xen/drivers/passthrough/vtd/iommu.c
> --- a/xen/drivers/passthrough/vtd/iommu.c	Thu Aug 25 12:03:14 2011 +0100
> +++ b/xen/drivers/passthrough/vtd/iommu.c	Tue Aug 30 15:15:56 2011 +0100
> @@ -971,7 +971,7 @@ static unsigned int dma_msi_startup(unsi
>      return 0;
>  }
>  
> -static void dma_msi_end(unsigned int irq)
> +static void dma_msi_end(unsigned int irq, u8 vector)
>  {
>      dma_msi_unmask(irq);
>      ack_APIC_irq();
> diff -r 227130622561 -r a95fd5d03c20 xen/include/xen/irq.h
> --- a/xen/include/xen/irq.h	Thu Aug 25 12:03:14 2011 +0100
> +++ b/xen/include/xen/irq.h	Tue Aug 30 15:15:56 2011 +0100
> @@ -44,7 +44,7 @@ struct hw_interrupt_type {
>      void (*enable)(unsigned int irq);
>      void (*disable)(unsigned int irq);
>      void (*ack)(unsigned int irq);
> -    void (*end)(unsigned int irq);
> +    void (*end)(unsigned int irq, u8 vector);
>      void (*set_affinity)(unsigned int irq, cpumask_t mask);
>  };
>  

-- 
Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer
T: +44 (0)1223 225 900, http://www.citrix.com