x86: pcie: fix allocating 1 vector under MSI-X

Fix an issue where 1 vector is being requested when MSI-X is
enabled. The previous logic always assumed the PCIE device has
only fixed or single MSI when we are requesting 1 vector, which
is not entirely correct. So if there is no vector allocated
already, try to allocate one.

Fixes #93319

Signed-off-by: Daniel Leung <[email protected]>

Author: dcpleung

arch/x86/core/pcie.c

@@ -249,12 +249,18 @@ uint8_t arch_pcie_msi_vectors_allocate(unsigned int priority,
 
 	for (i = 0; i < n_vector; i++) {
 		if (n_vector == 1) {
-			/* This path is taken by PCIE device with fixed
-			 * or single MSI: IRQ has been already allocated
-			 * and/or set on the PCIe bus. Thus we only require
-			 * to get it.
+			/* For PCIE device with fixed or single MSI: IRQ has
+			 * been already allocated and/or set on the PCIe bus.
+			 * We only need to retrieve it.
 			 */
 			irq = pcie_get_irq(vectors->bdf);
+
+			/* If that is not the case, we will need to allocate
+			 * IRQ before proceeding.
+			 */
+			if (irq == PCIE_CONF_INTR_IRQ_NONE) {
+				irq = arch_irq_allocate();
+			}
 		} else {
 			irq = arch_irq_allocate();
 		}