[xen staging] vpci: Hide legacy capability when it fails to initialize

[patchbot@xxxxxxx]

commit 4bd1ee8534742ba0922298cda50dbb404648f6dd
Author:     Jiqian Chen <Jiqian.Chen@xxxxxxx>
AuthorDate: Wed Jul 30 10:45:44 2025 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Wed Jul 30 12:04:08 2025 +0200

    vpci: Hide legacy capability when it fails to initialize
    
    When vpci fails to initialize a legacy capability of device, it just
    returns an error and vPCI gets disabled for the whole device.  That
    most likely renders the device unusable, plus possibly causing issues
    to Xen itself if guest attempts to program the native MSI or MSI-X
    capabilities if present.
    
    So, add new function to hide legacy capability when initialization
    fails. And remove the failed legacy capability from the vpci emulated
    legacy capability list.
    
    Signed-off-by: Jiqian Chen <Jiqian.Chen@xxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/drivers/vpci/vpci.c | 111 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 110 insertions(+), 1 deletion(-)

diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
index 7778acee0d..da67226e4f 100644
--- a/xen/drivers/vpci/vpci.c
+++ b/xen/drivers/vpci/vpci.c
@@ -83,6 +83,88 @@ static int assign_virtual_sbdf(struct pci_dev *pdev)
 
 #endif /* CONFIG_HAS_VPCI_GUEST_SUPPORT */
 
+static struct vpci_register *vpci_get_register(const struct vpci *vpci,
+                                               unsigned int offset,
+                                               unsigned int size)
+{
+    struct vpci_register *r;
+
+    ASSERT(spin_is_locked(&vpci->lock));
+
+    list_for_each_entry ( r, &vpci->handlers, node )
+    {
+        if ( r->offset == offset && r->size == size )
+            return r;
+
+        if ( offset <= r->offset )
+            break;
+    }
+
+    return NULL;
+}
+
+static struct vpci_register *vpci_get_previous_cap_register(
+    const struct vpci *vpci, unsigned int offset)
+{
+    unsigned int next;
+    struct vpci_register *r;
+
+    if ( offset < 0x40 )
+    {
+        ASSERT_UNREACHABLE();
+        return NULL;
+    }
+
+    for ( r = vpci_get_register(vpci, PCI_CAPABILITY_LIST, 1); r;
+          r = next >= 0x40 ? vpci_get_register(vpci,
+                                               next + PCI_CAP_LIST_NEXT, 1)
+                           : NULL )
+    {
+        next = (unsigned int)(uintptr_t)r->private;
+        ASSERT(next == (uintptr_t)r->private);
+        if ( next == offset )
+            break;
+    }
+
+    return r;
+}
+
+static int vpci_capability_hide(const struct pci_dev *pdev, unsigned int cap)
+{
+    const unsigned int offset = pci_find_cap_offset(pdev->sbdf, cap);
+    struct vpci_register *prev_r, *next_r;
+    struct vpci *vpci = pdev->vpci;
+
+    if ( !offset )
+    {
+        ASSERT_UNREACHABLE();
+        return 0;
+    }
+
+    spin_lock(&vpci->lock);
+    prev_r = vpci_get_previous_cap_register(vpci, offset);
+    next_r = vpci_get_register(vpci, offset + PCI_CAP_LIST_NEXT, 1);
+    if ( !prev_r || !next_r )
+    {
+        spin_unlock(&vpci->lock);
+        return -ENODEV;
+    }
+
+    prev_r->private = next_r->private;
+    /*
+     * Not calling vpci_remove_register() here is to avoid redoing
+     * the register search.
+     */
+    list_del(&next_r->node);
+    spin_unlock(&vpci->lock);
+    xfree(next_r);
+
+    if ( !is_hardware_domain(pdev->domain) )
+        return vpci_remove_register(vpci, offset + PCI_CAP_LIST_ID, 1);
+
+    return 0;
+}
+
 static int vpci_init_capabilities(struct pci_dev *pdev)
 {
     for ( unsigned int i = 0; i < NUM_VPCI_INIT; i++ )
@@ -103,7 +185,34 @@ static int vpci_init_capabilities(struct pci_dev *pdev)
 
         rc = capability->init(pdev);
         if ( rc )
-            return rc;
+        {
+            const char *type = is_ext ? "extended" : "legacy";
+
+            printk(XENLOG_WARNING
+                   "%pd %pp: init %s cap %u fail rc=%d, mask it\n",
+                   pdev->domain, &pdev->sbdf, type, cap, rc);
+
+            if ( capability->cleanup )
+            {
+                rc = capability->cleanup(pdev);
+                if ( rc )
+                {
+                    printk(XENLOG_ERR "%pd %pp: clean %s cap %u fail rc=%d\n",
+                           pdev->domain, &pdev->sbdf, type, cap, rc);
+                    if ( !is_hardware_domain(pdev->domain) )
+                        return rc;
+                }
+            }
+
+            if ( !is_ext )
+                rc = vpci_capability_hide(pdev, cap);
+            if ( rc )
+            {
+                printk(XENLOG_ERR "%pd %pp: hide %s cap %u fail rc=%d\n",
+                       pdev->domain, &pdev->sbdf, type, cap, rc);
+                return rc;
+            }
+        }
     }
 
     return 0;
--
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