[PATCH 2/3] x86/msi: remove return value from msi_set_mask_bit()

[David Vrabel <dvrabel@xxxxxxxxxx>]

The return value was only used for WARN()s or BUG()s so it has no
functional purpose. Simplify the code by removing it.

The meaning of the return value and the purpose of the various WARNs()
and BUGs() is rather unclear. The only failure path (where an MSI-X
vector needs to be masked but the MSI-X table is not accessible) has a
useful warning message.

Signed-off-by: David Vrabel <dvrabel@xxxxxxxxxxxx>

CR: https://code.amazon.com/reviews/CR-79020927
---
 xen/arch/x86/msi.c | 34 +++++++++-------------------------
 1 file changed, 9 insertions(+), 25 deletions(-)

diff --git a/xen/arch/x86/msi.c b/xen/arch/x86/msi.c
index 8bde6b9be1..6c675d11d1 100644
--- a/xen/arch/x86/msi.c
+++ b/xen/arch/x86/msi.c
@@ -314,7 +314,7 @@ int msi_maskable_irq(const struct msi_desc *entry)
            || entry->msi_attrib.maskbit;
 }
 
-static bool msi_set_mask_bit(struct irq_desc *desc, bool host, bool guest)
+static void msi_set_mask_bit(struct irq_desc *desc, bool host, bool guest)
 {
     struct msi_desc *entry = desc->msi_desc;
     struct pci_dev *pdev;
@@ -361,11 +361,6 @@ static bool msi_set_mask_bit(struct irq_desc *desc, bool 
host, bool guest)
 
             if ( likely(control & PCI_MSIX_FLAGS_ENABLE) )
                 break;
-
-            entry->msi_attrib.host_masked = host;
-            entry->msi_attrib.guest_masked = guest;
-
-            flag = true;
         }
         else if ( flag && !(control & PCI_MSIX_FLAGS_MASKALL) )
         {
@@ -385,14 +380,10 @@ static bool msi_set_mask_bit(struct irq_desc *desc, bool 
host, bool guest)
             control |= PCI_MSIX_FLAGS_MASKALL;
         pci_conf_write16(pdev->sbdf,
                          msix_control_reg(entry->msi_attrib.pos), control);
-        return flag;
-    default:
-        return 0;
+        break;
     }
     entry->msi_attrib.host_masked = host;
     entry->msi_attrib.guest_masked = guest;
-
-    return 1;
 }
 
 static int msi_get_mask_bit(const struct msi_desc *entry)
@@ -418,16 +409,12 @@ static int msi_get_mask_bit(const struct msi_desc *entry)
 
 void cf_check mask_msi_irq(struct irq_desc *desc)
 {
-    if ( unlikely(!msi_set_mask_bit(desc, 1,
-                                    desc->msi_desc->msi_attrib.guest_masked)) )
-        BUG_ON(!(desc->status & IRQ_DISABLED));
+    msi_set_mask_bit(desc, 1, desc->msi_desc->msi_attrib.guest_masked);
 }
 
 void cf_check unmask_msi_irq(struct irq_desc *desc)
 {
-    if ( unlikely(!msi_set_mask_bit(desc, 0,
-                                    desc->msi_desc->msi_attrib.guest_masked)) )
-        WARN();
+    msi_set_mask_bit(desc, 0, desc->msi_desc->msi_attrib.guest_masked);
 }
 
 void guest_mask_msi_irq(struct irq_desc *desc, bool mask)
@@ -437,15 +424,13 @@ void guest_mask_msi_irq(struct irq_desc *desc, bool mask)
 
 static unsigned int cf_check startup_msi_irq(struct irq_desc *desc)
 {
-    if ( unlikely(!msi_set_mask_bit(desc, 0, !!(desc->status & IRQ_GUEST))) )
-        WARN();
+    msi_set_mask_bit(desc, 0, !!(desc->status & IRQ_GUEST));
     return 0;
 }
 
 static void cf_check shutdown_msi_irq(struct irq_desc *desc)
 {
-    if ( unlikely(!msi_set_mask_bit(desc, 1, 1)) )
-        BUG_ON(!(desc->status & IRQ_DISABLED));
+    msi_set_mask_bit(desc, 1, 1);
 }
 
 void cf_check ack_nonmaskable_msi_irq(struct irq_desc *desc)
@@ -1358,10 +1343,9 @@ int pci_restore_msi_state(struct pci_dev *pdev)
 
         for ( i = 0; ; )
         {
-            if ( unlikely(!msi_set_mask_bit(desc,
-                                            entry[i].msi_attrib.host_masked,
-                                            entry[i].msi_attrib.guest_masked)) 
)
-                BUG();
+            msi_set_mask_bit(desc,
+                             entry[i].msi_attrib.host_masked,
+                             entry[i].msi_attrib.guest_masked);
 
             if ( !--nr )
                 break;
-- 
2.30.2