x86/msi: Change __msi_set_enable() to take pci_sbdf_t

This removes the unnecessary work of splitting a 32-bit number across
4 registers, and recombining later.  Bloat-o-meter reports:

  add/remove: 0/0 grow/shrink: 0/9 up/down: 0/-295 (-295)
  Function                                     old     new   delta
  enable_iommu                                1748    1732     -16
  iommu_msi_unmask                              98      81     -17
  iommu_msi_mask                               100      83     -17
  disable_iommu                                286     269     -17
  __msi_set_enable                              81      50     -31
  __pci_disable_msi                            178     146     -32
  pci_cleanup_msi                              268     229     -39
  pci_enable_msi                              1063    1019     -44
  pci_restore_msi_state                       1116    1034     -82

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/include/asm/msi.h

@@ -238,7 +238,7 @@ struct arch_msix {
 void early_msi_init(void);
 void msi_compose_msg(unsigned vector, const cpumask_t *cpu_mask,
                      struct msi_msg *msg);
-void __msi_set_enable(u16 seg, u8 bus, u8 slot, u8 func, int pos, int enable);
+void __msi_set_enable(pci_sbdf_t sbdf, int pos, int enable);
 void cf_check mask_msi_irq(struct irq_desc *desc);
 void cf_check unmask_msi_irq(struct irq_desc *desc);
 void guest_mask_msi_irq(struct irq_desc *desc, bool mask);

xen/arch/x86/msi.c

@@ -267,28 +267,22 @@ void cf_check set_msi_affinity(struct irq_desc *desc, const cpumask_t *mask)
     write_msi_msg(msi_desc, &msg);
 }
 
-void __msi_set_enable(u16 seg, u8 bus, u8 slot, u8 func, int pos, int enable)
+void __msi_set_enable(pci_sbdf_t sbdf, int pos, int enable)
 {
-    uint16_t control = pci_conf_read16(PCI_SBDF(seg, bus, slot, func),
-                                       pos + PCI_MSI_FLAGS);
+    uint16_t control = pci_conf_read16(sbdf, pos + PCI_MSI_FLAGS);
 
     control &= ~PCI_MSI_FLAGS_ENABLE;
     if ( enable )
         control |= PCI_MSI_FLAGS_ENABLE;
-    pci_conf_write16(PCI_SBDF(seg, bus, slot, func),
-                     pos + PCI_MSI_FLAGS, control);
+    pci_conf_write16(sbdf, pos + PCI_MSI_FLAGS, control);
 }
 
 static void msi_set_enable(struct pci_dev *dev, int enable)
 {
     unsigned int pos = dev->msi_pos;
-    u16 seg = dev->seg;
-    u8 bus = dev->bus;
-    u8 slot = PCI_SLOT(dev->devfn);
-    u8 func = PCI_FUNC(dev->devfn);
 
     if ( pos )
-        __msi_set_enable(seg, bus, slot, func, pos, enable);
+        __msi_set_enable(dev->sbdf, pos, enable);
 }
 
 static void msix_set_enable(struct pci_dev *dev, int enable)

xen/drivers/passthrough/amd/iommu_init.c

@@ -409,8 +409,9 @@ static void iommu_reset_log(struct amd_iommu *iommu,
 
 static void amd_iommu_msi_enable(struct amd_iommu *iommu, int flag)
 {
-    __msi_set_enable(iommu->seg, PCI_BUS(iommu->bdf), PCI_SLOT(iommu->bdf),
-                     PCI_FUNC(iommu->bdf), iommu->msi.msi_attrib.pos, flag);
+    pci_sbdf_t sbdf = { .seg = iommu->seg, .bdf = iommu->bdf };
+
+    __msi_set_enable(sbdf, iommu->msi.msi_attrib.pos, flag);
 }
 
 static void cf_check iommu_msi_unmask(struct irq_desc *desc)