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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 14/03/2025 8:51 am, Jan Beulich wrote:
> 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).

Indeed.  These are about the first 16 vectors in the IDT, and and aren't
related to ISA (or any other type) of IRQ.

~Andrew