Re: [PATCH] x86/irq: use NR_ISAIRQS instead of open-coded value

[Jan Beulich <jbeulich@xxxxxxxx>]

On 14.03.2025 02:20, dmkhn@xxxxxxxxx wrote:
> Replace the open-coded value 16 with the NR_ISAIRQS symbol to enhance
> readability.
> 
> No functional changes.
> 
> Signed-off-by: Denis Mukhin <dmukhin@xxxxxxxx>
> ---
>  xen/arch/x86/hvm/dm.c          |  2 +-
>  xen/arch/x86/hvm/irq.c         | 17 +++++++++--------
>  xen/arch/x86/hvm/vlapic.c      | 10 +++++-----
>  xen/arch/x86/hvm/vpic.c        |  4 ++--
>  xen/arch/x86/include/asm/irq.h |  2 +-
>  xen/arch/x86/io_apic.c         | 12 ++++++------
>  xen/arch/x86/irq.c             |  6 +++---
>  7 files changed, 27 insertions(+), 26 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/dm.c b/xen/arch/x86/hvm/dm.c
> index a1f7a4d30a..36d47664e9 100644
> --- a/xen/arch/x86/hvm/dm.c
> +++ b/xen/arch/x86/hvm/dm.c
> @@ -90,7 +90,7 @@ static int set_pci_intx_level(struct domain *d, uint16_t 
> domain,
>  static int set_isa_irq_level(struct domain *d, uint8_t isa_irq,
>                               uint8_t level)
>  {
> -    if ( isa_irq > 15 )
> +    if ( isa_irq >= NR_ISAIRQS )
>          return -EINVAL;
>  
>      switch ( level )
> diff --git a/xen/arch/x86/hvm/irq.c b/xen/arch/x86/hvm/irq.c
> index 1eab44defc..1f7d8ca43e 100644
> --- a/xen/arch/x86/hvm/irq.c
> +++ b/xen/arch/x86/hvm/irq.c
> @@ -209,7 +209,7 @@ int hvm_isa_irq_assert(struct domain *d, unsigned int 
> isa_irq,
>      unsigned int gsi = hvm_isa_irq_to_gsi(isa_irq);
>      int vector = -1;
>  
> -    ASSERT(isa_irq <= 15);
> +    ASSERT(isa_irq < NR_ISAIRQS);
>  
>      spin_lock(&d->arch.hvm.irq_lock);
>  
> @@ -231,7 +231,7 @@ void hvm_isa_irq_deassert(
>      struct hvm_irq *hvm_irq = hvm_domain_irq(d);
>      unsigned int gsi = hvm_isa_irq_to_gsi(isa_irq);
>  
> -    ASSERT(isa_irq <= 15);
> +    ASSERT(isa_irq < NR_ISAIRQS);
>  
>      spin_lock(&d->arch.hvm.irq_lock);
>  
> @@ -266,12 +266,12 @@ static void hvm_set_callback_irq_level(struct vcpu *v)
>          if ( asserted && (hvm_irq->gsi_assert_count[gsi]++ == 0) )
>          {
>              vioapic_irq_positive_edge(d, gsi);
> -            if ( gsi <= 15 )
> +            if ( gsi < NR_ISAIRQS )
>                  vpic_irq_positive_edge(d, gsi);
>          }
>          else if ( !asserted && (--hvm_irq->gsi_assert_count[gsi] == 0) )
>          {
> -            if ( gsi <= 15 )
> +            if ( gsi < NR_ISAIRQS )
>                  vpic_irq_negative_edge(d, gsi);
>          }
>          break;
> @@ -328,7 +328,7 @@ int hvm_set_pci_link_route(struct domain *d, u8 link, u8 
> isa_irq)
>      u8 old_isa_irq;
>      int i;
>  
> -    if ( (link > 3) || (isa_irq > 15) )
> +    if ( (link > 3) || (isa_irq >= NR_ISAIRQS) )
>          return -EINVAL;
>  
>      spin_lock(&d->arch.hvm.irq_lock);
> @@ -440,7 +440,8 @@ void hvm_set_callback_via(struct domain *d, uint64_t via)
>          {
>          case HVMIRQ_callback_gsi:
>              gsi = hvm_irq->callback_via.gsi;
> -            if ( (--hvm_irq->gsi_assert_count[gsi] == 0) && (gsi <= 15) )
> +            if ( (--hvm_irq->gsi_assert_count[gsi] == 0) &&
> +                 (gsi < NR_ISAIRQS) )
>                  vpic_irq_negative_edge(d, gsi);
>              break;
>          case HVMIRQ_callback_pci_intx:
> @@ -464,7 +465,7 @@ void hvm_set_callback_via(struct domain *d, uint64_t via)
>                    (hvm_irq->gsi_assert_count[gsi]++ == 0) )
>          {
>              vioapic_irq_positive_edge(d, gsi);
> -            if ( gsi <= 15 )
> +            if ( gsi < NR_ISAIRQS )
>                  vpic_irq_positive_edge(d, gsi);
>          }
>          break;
> @@ -764,7 +765,7 @@ static int cf_check irq_check_link(const struct domain *d,
>              return -EINVAL;
>  
>      for ( link = 0; link < ARRAY_SIZE(pci_link->route); link++ )
> -        if ( pci_link->route[link] > 15 )
> +        if ( pci_link->route[link] >= NR_ISAIRQS )
>          {
>              printk(XENLOG_G_ERR
>                     "HVM restore: PCI-ISA link %u out of range (%u)\n",

Up to here I agree with the adjustments made, but ...

> --- a/xen/arch/x86/hvm/vlapic.c
> +++ b/xen/arch/x86/hvm/vlapic.c
> @@ -123,7 +123,7 @@ static void vlapic_error(struct vlapic *vlapic, unsigned 
> int err_bit)
>               * will end up back here.  Break the cycle by only injecting 
> LVTERR
>               * if it will succeed, and folding in RECVILL otherwise.
>               */
> -            if ( (lvterr & APIC_VECTOR_MASK) >= 16 )
> +            if ( (lvterr & APIC_VECTOR_MASK) >= NR_ISAIRQS )
>                  inj = true;
>              else
>                  set_bit(ilog2(APIC_ESR_RECVILL), &vlapic->hw.pending_esr);
> @@ -136,7 +136,7 @@ static void vlapic_error(struct vlapic *vlapic, unsigned 
> int err_bit)
>  
>  bool vlapic_test_irq(const struct vlapic *vlapic, uint8_t vec)
>  {
> -    if ( unlikely(vec < 16) )
> +    if ( unlikely(vec < NR_ISAIRQS) )
>          return false;
>  
>      if ( hvm_funcs.test_pir &&
> @@ -150,7 +150,7 @@ void vlapic_set_irq(struct vlapic *vlapic, uint8_t vec, 
> uint8_t trig)
>  {
>      struct vcpu *target = vlapic_vcpu(vlapic);
>  
> -    if ( unlikely(vec < 16) )
> +    if ( unlikely(vec < NR_ISAIRQS) )
>      {
>          vlapic_error(vlapic, ilog2(APIC_ESR_RECVILL));
>          return;
> @@ -523,7 +523,7 @@ void vlapic_ipi(
>          struct vlapic *target = vlapic_lowest_prio(
>              vlapic_domain(vlapic), vlapic, short_hand, dest, dest_mode);
>  
> -        if ( unlikely((icr_low & APIC_VECTOR_MASK) < 16) )
> +        if ( unlikely((icr_low & APIC_VECTOR_MASK) < NR_ISAIRQS) )
>              vlapic_error(vlapic, ilog2(APIC_ESR_SENDILL));
>          else if ( target )
>              vlapic_accept_irq(vlapic_vcpu(target), icr_low);
> @@ -531,7 +531,7 @@ void vlapic_ipi(
>      }
>  
>      case APIC_DM_FIXED:
> -        if ( unlikely((icr_low & APIC_VECTOR_MASK) < 16) )
> +        if ( unlikely((icr_low & APIC_VECTOR_MASK) < NR_ISAIRQS) )
>          {
>              vlapic_error(vlapic, ilog2(APIC_ESR_SENDILL));
>              break;

... the 16 here has a different origin (in the local APIC spec). Changes
further down look okay again.

Jan