Merge tag 'for-linus-6.15-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen updates from Juergen Gross:

 - cleanup: remove an used function

 - add support for a XenServer specific virtual PCI device

 - fix the handling of a sparse Xen hypervisor symbol table

 - avoid warnings when building the kernel with gcc 15

 - fix use of devices behind a VMD bridge when running as a Xen PV dom0

* tag 'for-linus-6.15-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  PCI/MSI: Convert pci_msi_ignore_mask to per MSI domain flag
  PCI: vmd: Disable MSI remapping bypass under Xen
  xen/pci: Do not register devices with segments >= 0x10000
  xen/pciback: Remove unused pcistub_get_pci_dev
  xenfs/xensyms: respect hypervisor's "next" indication
  xen/mcelog: Add __nonstring annotations for unterminated strings
  xen: Add support for XenServer 6.1 platform device

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
index 9d9596947350..e619accca49d 100644
--- a/drivers/pci/controller/vmd.c
+++ b/drivers/pci/controller/vmd.c
@@ -17,6 +17,8 @@
 #include <linux/rculist.h>
 #include <linux/rcupdate.h>
 
+#include <xen/xen.h>
+
 #include <asm/irqdomain.h>
 
 #define VMD_CFGBAR	0
@@ -970,6 +972,24 @@ static int vmd_probe(struct pci_dev *dev, const struct pci_device_id *id)
 	struct vmd_dev *vmd;
 	int err;
 
+	if (xen_domain()) {
+		/*
+		 * Xen doesn't have knowledge about devices in the VMD bus
+		 * because the config space of devices behind the VMD bridge is
+		 * not known to Xen, and hence Xen cannot discover or configure
+		 * them in any way.
+		 *
+		 * Bypass of MSI remapping won't work in that case as direct
+		 * write by Linux to the MSI entries won't result in functional
+		 * interrupts, as Xen is the entity that manages the host
+		 * interrupt controller and must configure interrupts.  However
+		 * multiplexing of interrupts by the VMD bridge will work under
+		 * Xen, so force the usage of that mode which must always be
+		 * supported by VMD bridges.
+		 */
+		features &= ~VMD_FEAT_CAN_BYPASS_MSI_REMAP;
+	}
+
 	if (resource_size(&dev->resource[VMD_CFGBAR]) < (1 << 20))
 		return -ENOMEM;