Honor the disabled setting for MSI-X interrupts for passthrough devices.

Add a new ioctl to disable all MSI-X interrupts for a PCI passthrough
device and invoke it if a write to the MSI-X capability registers
disables MSI-X.  This avoids leaving MSI-X interrupts enabled on the
host if a guest device driver has disabled them (e.g. as part of
detaching a guest device driver).

This was found by Chelsio QA when testing that a Linux guest could
switch from MSI-X to MSI interrupts when using the cxgb4vf driver.

While here, explicitly fail requests to enable MSI on a passthrough
device if MSI-X is enabled and vice versa.

Reported by:	Sony Arpita Das @ Chelsio
Reviewed by:	grehan, markj
MFC after:	2 weeks
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D27212

1 files changed, 5 insertions, 0 deletions

diff --git a/usr.sbin/bhyve/pci_passthru.c b/usr.sbin/bhyve/pci_passthru.c
index 85c2e52188b3a..3305a4854812c 100644
--- a/usr.sbin/bhyve/pci_passthru.c
+++ b/usr.sbin/bhyve/pci_passthru.c
@@ -869,6 +869,11 @@ passthru_cfgwrite(struct vmctx *ctx, int vcpu, struct pci_devinst *pi,
 				if (error)
 					err(1, "vm_setup_pptdev_msix");
 			}
+		} else {
+			error = vm_disable_pptdev_msix(ctx, sc->psc_sel.pc_bus,
+			    sc->psc_sel.pc_dev, sc->psc_sel.pc_func);
+			if (error)
+				err(1, "vm_disable_pptdev_msix");
 		}
 		return (0);
 	}