[PATCH v6 2/3] xen/pci: introduce PF<->VF links

[Stewart Hildebrand <stewart.hildebrand@xxxxxxx>]

Add links between a VF's struct pci_dev and its associated PF struct
pci_dev. Move the calls to pci_get_pdev()/pci_add_device() down to avoid
dropping and re-acquiring the pcidevs_lock().

During PF removal, unlink VF from PF and mark the VF broken. As before,
VFs may exist without a corresponding PF, although now only with
pdev->broken = true.

The hardware domain is expected to remove the associated VFs before
removing the PF. Print a warning in case a PF is removed with associated
VFs still present.

Signed-off-by: Stewart Hildebrand <stewart.hildebrand@xxxxxxx>
---
Candidate for backport to 4.19 (the next patch depends on this one)

v5->v6:
* move printk() before ASSERT_UNREACHABLE()
* warn about PF removal with VFs still present
* clarify commit message

v4->v5:
* new patch, split from ("x86/msi: fix locking for SR-IOV devices")
* move INIT_LIST_HEAD(&pdev->vf_list); earlier
* collapse struct list_head instances
* retain error code from pci_add_device()
* unlink (and mark broken) VFs instead of removing them
* const-ify VF->PF link
---
 xen/drivers/passthrough/pci.c | 76 ++++++++++++++++++++++++++++-------
 xen/include/xen/pci.h         | 10 +++++
 2 files changed, 72 insertions(+), 14 deletions(-)

diff --git a/xen/drivers/passthrough/pci.c b/xen/drivers/passthrough/pci.c
index 74d3895e1ef6..fe31255b1207 100644
--- a/xen/drivers/passthrough/pci.c
+++ b/xen/drivers/passthrough/pci.c
@@ -333,6 +333,8 @@ static struct pci_dev *alloc_pdev(struct pci_seg *pseg, u8 
bus, u8 devfn)
     *((u8*) &pdev->devfn) = devfn;
     pdev->domain = NULL;
 
+    INIT_LIST_HEAD(&pdev->vf_list);
+
     arch_pci_init_pdev(pdev);
 
     rc = pdev_msi_init(pdev);
@@ -449,6 +451,10 @@ static void free_pdev(struct pci_seg *pseg, struct pci_dev 
*pdev)
 
     list_del(&pdev->alldevs_list);
     pdev_msi_deinit(pdev);
+
+    if ( pdev->info.is_virtfn && pdev->virtfn.pf_pdev )
+        list_del(&pdev->vf_list);
+
     xfree(pdev);
 }
 
@@ -656,24 +662,11 @@ int pci_add_device(u16 seg, u8 bus, u8 devfn,
     unsigned int slot = PCI_SLOT(devfn), func = PCI_FUNC(devfn);
     const char *type;
     int ret;
-    bool pf_is_extfn = false;
 
     if ( !info )
         type = "device";
     else if ( info->is_virtfn )
-    {
-        pcidevs_lock();
-        pdev = pci_get_pdev(NULL,
-                            PCI_SBDF(seg, info->physfn.bus,
-                                     info->physfn.devfn));
-        if ( pdev )
-            pf_is_extfn = pdev->info.is_extfn;
-        pcidevs_unlock();
-        if ( !pdev )
-            pci_add_device(seg, info->physfn.bus, info->physfn.devfn,
-                           NULL, node);
         type = "virtual function";
-    }
     else if ( info->is_extfn )
         type = "extended function";
     else
@@ -703,7 +696,44 @@ int pci_add_device(u16 seg, u8 bus, u8 devfn,
          * extended function.
          */
         if ( pdev->info.is_virtfn )
-            pdev->info.is_extfn = pf_is_extfn;
+        {
+            struct pci_dev *pf_pdev;
+
+            pf_pdev = pci_get_pdev(NULL,
+                                   PCI_SBDF(seg, info->physfn.bus,
+                                            info->physfn.devfn));
+
+            if ( !pf_pdev )
+            {
+                ret = pci_add_device(seg, info->physfn.bus, info->physfn.devfn,
+                                     NULL, node);
+                if ( ret )
+                {
+                    printk(XENLOG_WARNING "Failed to add SR-IOV device PF %pp 
for VF %pp\n",
+                           &PCI_SBDF(seg, info->physfn.bus, 
info->physfn.devfn),
+                           &pdev->sbdf);
+                    free_pdev(pseg, pdev);
+                    goto out;
+                }
+                pf_pdev = pci_get_pdev(NULL,
+                                       PCI_SBDF(seg, info->physfn.bus,
+                                                info->physfn.devfn));
+                if ( !pf_pdev )
+                {
+                    printk(XENLOG_ERR "Failed to find SR-IOV device PF %pp for 
VF %pp\n",
+                           &PCI_SBDF(seg, info->physfn.bus, 
info->physfn.devfn),
+                           &pdev->sbdf);
+                    ASSERT_UNREACHABLE();
+                    free_pdev(pseg, pdev);
+                    ret = -EILSEQ;
+                    goto out;
+                }
+            }
+
+            pdev->info.is_extfn = pf_pdev->info.is_extfn;
+            pdev->virtfn.pf_pdev = pf_pdev;
+            list_add(&pdev->vf_list, &pf_pdev->vf_list);
+        }
     }
 
     if ( !pdev->info.is_virtfn && !pdev->vf_rlen[0] )
@@ -821,6 +851,24 @@ int pci_remove_device(u16 seg, u8 bus, u8 devfn)
     list_for_each_entry ( pdev, &pseg->alldevs_list, alldevs_list )
         if ( pdev->bus == bus && pdev->devfn == devfn )
         {
+            if ( !pdev->info.is_virtfn )
+            {
+                struct pci_dev *vf_pdev, *tmp;
+                bool warn_stale_vfs = false;
+
+                list_for_each_entry_safe(vf_pdev, tmp, &pdev->vf_list, vf_list)
+                {
+                    list_del(&vf_pdev->vf_list);
+                    vf_pdev->virtfn.pf_pdev = NULL;
+                    vf_pdev->broken = true;
+                    warn_stale_vfs = true;
+                }
+
+                if ( warn_stale_vfs )
+                    printk(XENLOG_WARNING "PCI SR-IOV PF %pp removed with VFs 
still present\n",
+                           &pdev->sbdf);
+            }
+
             if ( pdev->domain )
             {
                 write_lock(&pdev->domain->pci_lock);
diff --git a/xen/include/xen/pci.h b/xen/include/xen/pci.h
index ef56e80651d6..2ea168d5f914 100644
--- a/xen/include/xen/pci.h
+++ b/xen/include/xen/pci.h
@@ -153,7 +153,17 @@ struct pci_dev {
         unsigned int count;
 #define PT_FAULT_THRESHOLD 10
     } fault;
+
+    /*
+     * List head if info.is_virtfn == false
+     * List entry if info.is_virtfn == true
+     */
+    struct list_head vf_list;
     u64 vf_rlen[6];
+    struct {
+        /* Only populated for VFs (info.is_virtfn == true) */
+        const struct pci_dev *pf_pdev;        /* Link from VF to PF */
+    } virtfn;
 
     /* Data for vPCI. */
     struct vpci *vpci;
-- 
2.47.0