xen/pci: Install vpci handlers on x86 and fix error paths

Xen might not be able to discover at boot time all devices or some devices
might appear after specific actions from dom0.
In this case dom0 can use the PHYSDEVOP_pci_device_add to signal some
PCI devices to Xen.
As those devices where not known from Xen before, the vpci handlers must
be properly installed during pci_device_add for x86 PVH Dom0, in the
same way as what is done currently on arm (where Xen does not detect PCI
devices but relies on Dom0 to declare them all the time).

So this patch is removing the ifdef protecting the call to
vpci_add_handlers and the comment which was arm specific.

vpci_add_handlers is called on during pci_device_add which can be called
at runtime through hypercall physdev_op.
Remove __hwdom_init as the call is not limited anymore to hardware
domain init and fix linker script to only keep vpci_array in rodata
section.

Add missing vpci handlers cleanup during pci_device_remove and in case
of error with iommu during pci_device_add.

Move code adding the domain to the pdev domain_list as vpci_add_handlers
needs this to be set and remove it from the list in the error path.

Exit early of vpci_remove_device if the domain has no vpci support.

Add empty static inline for vpci_remove_device when CONFIG_VPCI is not
defined.

Add an ASSERT in vpci_add_handlers to check that the function is not
called twice for the same device.

Fixes: d59168dc05 ("xen/arm: Enable the existing x86 virtual PCI support for ARM")
Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Bertrand Marquis <bertrand.marquis@arm.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Julien Grall <jgrall@amazon.com>

xen/arch/arm/xen.lds.S

@@ -60,7 +60,7 @@ SECTIONS
        *(.proc.info)
        __proc_info_end = .;
 
-#if defined(CONFIG_HAS_VPCI) && defined(CONFIG_LATE_HWDOM)
+#ifdef CONFIG_HAS_VPCI
        . = ALIGN(POINTER_ALIGN);
        __start_vpci_array = .;
        *(SORT(.data.vpci.*))
@@ -189,13 +189,6 @@ SECTIONS
        *(.init_array)
        *(SORT(.init_array.*))
        __ctors_end = .;
-
-#if defined(CONFIG_HAS_VPCI) && !defined(CONFIG_LATE_HWDOM)
-       . = ALIGN(POINTER_ALIGN);
-       __start_vpci_array = .;
-       *(SORT(.data.vpci.*))
-       __end_vpci_array = .;
-#endif
   } :text
   __init_end_efi = .;
   . = ALIGN(STACK_SIZE);

xen/arch/x86/xen.lds.S

@@ -134,7 +134,7 @@ SECTIONS
        *(.ex_table.pre)
        __stop___pre_ex_table = .;
 
-#if defined(CONFIG_HAS_VPCI) && defined(CONFIG_LATE_HWDOM)
+#ifdef CONFIG_HAS_VPCI
        . = ALIGN(POINTER_ALIGN);
        __start_vpci_array = .;
        *(SORT(.data.vpci.*))
@@ -247,13 +247,6 @@ SECTIONS
        *(.init_array)
        *(SORT(.init_array.*))
        __ctors_end = .;
-
-#if defined(CONFIG_HAS_VPCI) && !defined(CONFIG_LATE_HWDOM)
-       . = ALIGN(POINTER_ALIGN);
-       __start_vpci_array = .;
-       *(SORT(.data.vpci.*))
-       __end_vpci_array = .;
-#endif
   } PHDR(text)
 
   . = ALIGN(SECTION_ALIGN);

xen/drivers/passthrough/pci.c

@@ -756,27 +756,28 @@ int pci_add_device(u16 seg, u8 bus, u8 devfn,
     if ( !pdev->domain )
     {
         pdev->domain = hardware_domain;
-#ifdef CONFIG_ARM
+        list_add(&pdev->domain_list, &hardware_domain->pdev_list);
+
         /*
-         * On ARM PCI devices discovery will be done by Dom0. Add vpci handler
-         * when Dom0 inform XEN to add the PCI devices in XEN.
+         * For devices not discovered by Xen during boot, add vPCI handlers
+         * when Dom0 first informs Xen about such devices.
          */
         ret = vpci_add_handlers(pdev);
         if ( ret )
         {
             printk(XENLOG_ERR "Setup of vPCI failed: %d\n", ret);
+            list_del(&pdev->domain_list);
             pdev->domain = NULL;
             goto out;
         }
-#endif
         ret = iommu_add_device(pdev);
         if ( ret )
         {
+            vpci_remove_device(pdev);
+            list_del(&pdev->domain_list);
             pdev->domain = NULL;
             goto out;
         }
-
-        list_add(&pdev->domain_list, &hardware_domain->pdev_list);
     }
     else
         iommu_enable_device(pdev);
@@ -819,6 +820,7 @@ 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 )
         {
+            vpci_remove_device(pdev);
             pci_cleanup_msi(pdev);
             ret = iommu_remove_device(pdev);
             if ( pdev->domain )

xen/drivers/vpci/vpci.c

@@ -37,6 +37,9 @@ extern vpci_register_init_t *const __end_vpci_array[];
 
 void vpci_remove_device(struct pci_dev *pdev)
 {
+    if ( !has_vpci(pdev->domain) )
+        return;
+
     spin_lock(&pdev->vpci->lock);
     while ( !list_empty(&pdev->vpci->handlers) )
     {
@@ -54,7 +57,7 @@ void vpci_remove_device(struct pci_dev *pdev)
     pdev->vpci = NULL;
 }
 
-int __hwdom_init vpci_add_handlers(struct pci_dev *pdev)
+int vpci_add_handlers(struct pci_dev *pdev)
 {
     unsigned int i;
     int rc = 0;
@@ -62,6 +65,9 @@ int __hwdom_init vpci_add_handlers(struct pci_dev *pdev)
     if ( !has_vpci(pdev->domain) )
         return 0;
 
+    /* We should not get here twice for the same device. */
+    ASSERT(!pdev->vpci);
+
     pdev->vpci = xzalloc(struct vpci);
     if ( !pdev->vpci )
         return -ENOMEM;

xen/include/xen/vpci.h

@@ -230,6 +230,8 @@ static inline int vpci_add_handlers(struct pci_dev *pdev)
     return 0;
 }
 
+static inline void vpci_remove_device(struct pci_dev *pdev) { }
+
 static inline void vpci_dump_msi(void) { }
 
 static inline uint32_t vpci_read(pci_sbdf_t sbdf, unsigned int reg,