[xen staging-4.19] xen/vpci: fix backport of 53859596c0d3

[patchbot@xxxxxxx]

commit 8a62bb04e27fe1e3e59d6551df5452c4e27683bd
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Wed Oct 22 13:44:01 2025 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Oct 22 13:44:01 2025 +0200

    xen/vpci: fix backport of 53859596c0d3
    
    Commit 53859596c0d3 depends on the behavioral change introduced in
    ee2eb6849d50 that inverted the initialization of the MSI-X and header vPCI
    handlers.  53859596c0d3 requires the header to be initialized before MSI-X.
    
    Change the order of initialization and adjust init_msix() to carve holes
    for the MSI-X tables if necessary, since it will now run after the BARs
    have been possibly mapped into the domain p2m.
    
    Fixes: 50b649c74272 ("vpci/msix: improve handling of bogus MSI-X 
capabilities")
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/drivers/vpci/header.c | 2 +-
 xen/drivers/vpci/msix.c   | 9 +++++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
index 1f48f2aac6..b002eb2072 100644
--- a/xen/drivers/vpci/header.c
+++ b/xen/drivers/vpci/header.c
@@ -1016,7 +1016,7 @@ static int cf_check init_header(struct pci_dev *pdev)
     pci_conf_write16(pdev->sbdf, PCI_COMMAND, cmd);
     return rc;
 }
-REGISTER_VPCI_INIT(init_header, VPCI_PRIORITY_MIDDLE);
+REGISTER_VPCI_INIT(init_header, VPCI_PRIORITY_HIGH);
 
 /*
  * Local variables:
diff --git a/xen/drivers/vpci/msix.c b/xen/drivers/vpci/msix.c
index 7d6e691b36..140f5ab284 100644
--- a/xen/drivers/vpci/msix.c
+++ b/xen/drivers/vpci/msix.c
@@ -790,9 +790,14 @@ static int cf_check init_msix(struct pci_dev *pdev)
     pdev->vpci->msix = msix;
     list_add(&msix->next, &d->arch.hvm.msix_tables);
 
-    return 0;
+    /*
+     * vPCI header initialization will have mapped the whole BAR into the
+     * p2m, as MSI-X capability was not yet initialized.  Crave a hole for
+     * the MSI-X table here, so that Xen can trap accesses.
+     */
+    return vpci_make_msix_hole(pdev);
 }
-REGISTER_VPCI_INIT(init_msix, VPCI_PRIORITY_HIGH);
+REGISTER_VPCI_INIT(init_msix, VPCI_PRIORITY_MIDDLE);
 
 /*
  * Local variables:
--
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