LinuxKPI: fix pci_alloc_irq_vectors() for MSI

pci_alloc_irq_vectors() is given a min and max vector value.
pci_enable_msi() will always succeed independent of these arguments as
it does not know about them.  Further it will only ever allocate
1 "vector" not supporting any other amount.
So upfront check that (a) the available pci_msi_count() can satisfy the
requested minv and (b) given the pci_enable_msi() hard coded limit check
that minv is not larger than 1.
If we cannot satisfy either requirement return an error.

This fixes problems with drivers which check that the returned value
of allocated "vectors" will match their requests and only otherwise try
to fall back to ask for 1 or deal otherwise.

Sponsored by:	The FreeBSD Foundation
Reviewed by:	hselasky (earlier version)
Differential Revision: https://reviews.freebsd.org/D37522

(cherry picked from commit e9715b1c4474333ff119aba3a9a74bff91f72372)

1 files changed, 5 insertions, 0 deletions

diff --git a/sys/compat/linuxkpi/common/src/linux_pci.c b/sys/compat/linuxkpi/common/src/linux_pci.c
index b0820c9b2c3e..a9c859d29623 100644
--- a/sys/compat/linuxkpi/common/src/linux_pci.c
+++ b/sys/compat/linuxkpi/common/src/linux_pci.c
@@ -928,6 +928,11 @@ out:
 			return (pdev->dev.irq_end - pdev->dev.irq_start);
 	}
 	if (flags & PCI_IRQ_MSI) {
+		if (pci_msi_count(pdev->dev.bsddev) < minv)
+			return (-ENOSPC);
+		/* We only support 1 vector in pci_enable_msi() */
+		if (minv != 1)
+			return (-ENOSPC);
 		error = pci_enable_msi(pdev);
 		if (error == 0 && pdev->msi_enabled)
 			return (pdev->dev.irq_end - pdev->dev.irq_start);