[PATCH v5 12/14] xen/arm: translate virtual PCI bus topology for guests

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>

There are three  originators for the PCI configuration space access:
1. The domain that owns physical host bridge: MMIO handlers are
there so we can update vPCI register handlers with the values
written by the hardware domain, e.g. physical view of the registers
vs guest's view on the configuration space.
2. Guest access to the passed through PCI devices: we need to properly
map virtual bus topology to the physical one, e.g. pass the configuration
space access to the corresponding physical devices.
3. Emulated host PCI bridge access. It doesn't exist in the physical
topology, e.g. it can't be mapped to some physical host bridge.
So, all access to the host bridge itself needs to be trapped and
emulated.

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@xxxxxxxx>
---
Since v4:
- indentation fixes
- constify struct domain
- updated commit message
- updates to the new locking scheme (pdev->vpci_lock)
Since v3:
- revisit locking
- move code to vpci.c
Since v2:
 - pass struct domain instead of struct vcpu
 - constify arguments where possible
 - gate relevant code with CONFIG_HAS_VPCI_GUEST_SUPPORT
New in v2
---
 xen/arch/arm/vpci.c     | 18 ++++++++++++++++++
 xen/drivers/vpci/vpci.c | 27 +++++++++++++++++++++++++++
 xen/include/xen/vpci.h  |  1 +
 3 files changed, 46 insertions(+)

diff --git a/xen/arch/arm/vpci.c b/xen/arch/arm/vpci.c
index 8e801f275879..3d134f42d07e 100644
--- a/xen/arch/arm/vpci.c
+++ b/xen/arch/arm/vpci.c
@@ -41,6 +41,15 @@ static int vpci_mmio_read(struct vcpu *v, mmio_info_t *info,
     /* data is needed to prevent a pointer cast on 32bit */
     unsigned long data;
 
+#ifdef CONFIG_HAS_VPCI_GUEST_SUPPORT
+    /*
+     * For the passed through devices we need to map their virtual SBDF
+     * to the physical PCI device being passed through.
+     */
+    if ( !bridge && !vpci_translate_virtual_device(v->domain, &sbdf) )
+        return 1;
+#endif
+
     if ( vpci_ecam_read(sbdf, ECAM_REG_OFFSET(info->gpa),
                         1U << info->dabt.size, &data) )
     {
@@ -59,6 +68,15 @@ static int vpci_mmio_write(struct vcpu *v, mmio_info_t *info,
     struct pci_host_bridge *bridge = p;
     pci_sbdf_t sbdf = vpci_sbdf_from_gpa(bridge, info->gpa);
 
+#ifdef CONFIG_HAS_VPCI_GUEST_SUPPORT
+    /*
+     * For the passed through devices we need to map their virtual SBDF
+     * to the physical PCI device being passed through.
+     */
+    if ( !bridge && !vpci_translate_virtual_device(v->domain, &sbdf) )
+        return 1;
+#endif
+
     return vpci_ecam_write(sbdf, ECAM_REG_OFFSET(info->gpa),
                            1U << info->dabt.size, r);
 }
diff --git a/xen/drivers/vpci/vpci.c b/xen/drivers/vpci/vpci.c
index c2fb4d4db233..bdc8c63f73fa 100644
--- a/xen/drivers/vpci/vpci.c
+++ b/xen/drivers/vpci/vpci.c
@@ -195,6 +195,33 @@ static void vpci_remove_virtual_device(struct domain *d,
     pdev->vpci->guest_sbdf.sbdf = ~0;
 }
 
+/*
+ * Find the physical device which is mapped to the virtual device
+ * and translate virtual SBDF to the physical one.
+ */
+bool vpci_translate_virtual_device(const struct domain *d, pci_sbdf_t *sbdf)
+{
+    struct pci_dev *pdev;
+
+    for_each_pdev( d, pdev )
+    {
+        bool found;
+
+        spin_lock(&pdev->vpci_lock);
+        found = pdev->vpci && (pdev->vpci->guest_sbdf.sbdf == sbdf->sbdf);
+        spin_unlock(&pdev->vpci_lock);
+
+        if ( found )
+        {
+            /* Replace guest SBDF with the physical one. */
+            *sbdf = pdev->sbdf;
+            return true;
+        }
+    }
+
+    return false;
+}
+
 /* Notify vPCI that device is assigned to guest. */
 int vpci_assign_device(struct domain *d, struct pci_dev *pdev)
 {
diff --git a/xen/include/xen/vpci.h b/xen/include/xen/vpci.h
index e5258bd7ce90..21d76929391f 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -280,6 +280,7 @@ static inline void vpci_cancel_pending_locked(struct 
pci_dev *pdev)
 /* Notify vPCI that device is assigned/de-assigned to/from guest. */
 int vpci_assign_device(struct domain *d, struct pci_dev *pdev);
 int vpci_deassign_device(struct domain *d, struct pci_dev *pdev);
+bool vpci_translate_virtual_device(const struct domain *d, pci_sbdf_t *sbdf);
 #else
 static inline int vpci_assign_device(struct domain *d, struct pci_dev *pdev)
 {
-- 
2.25.1