[PATCH v6 12/13] xen/arm: translate virtual PCI bus topology for guests

[Oleksandr Andrushchenko <andr2000@gmail.com>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

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@epam.com>
---
Since v5:
- add vpci_translate_virtual_device for #ifndef CONFIG_HAS_VPCI_GUEST_SUPPORT
  case to simplify ifdefery
- add ASSERT(!is_hardware_domain(d)); to vpci_translate_virtual_device
- reset output register on failed virtual SBDF translation
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     | 17 +++++++++++++++++
 xen/drivers/vpci/vpci.c | 29 +++++++++++++++++++++++++++++
 xen/include/xen/vpci.h  |  7 +++++++
 3 files changed, 53 insertions(+)

diff --git a/xen/arch/arm/vpci.c b/xen/arch/arm/vpci.c
index a9fc5817f94e..84b2b068a0fe 100644
--- a/xen/arch/arm/vpci.c
+++ b/xen/arch/arm/vpci.c
@@ -41,6 +41,16 @@ 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;
 
+    /*
+     * 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) )
+    {
+        *r = ~0ul;
+        return 1;
+    }
+
     if ( vpci_ecam_read(sbdf, ECAM_REG_OFFSET(info->gpa),
                         1U << info->dabt.size, &data) )
     {
@@ -59,6 +69,13 @@ 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);
 
+    /*
+     * 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;
+
     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 7d422d11f83d..070db7391391 100644
--- a/xen/drivers/vpci/vpci.c
+++ b/xen/drivers/vpci/vpci.c
@@ -168,6 +168,35 @@ 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;
+
+    ASSERT(!is_hardware_domain(d));
+
+    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 1f04d34a2369..f6eb9f2051af 100644
--- a/xen/include/xen/vpci.h
+++ b/xen/include/xen/vpci.h
@@ -271,6 +271,7 @@ static inline bool __must_check vpci_process_pending(struct vcpu *v)
 /* Notify vPCI that device is assigned/de-assigned to/from guest. */
 int vpci_assign_device(struct domain *d, struct pci_dev *pdev);
 void 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)
 {
@@ -280,6 +281,12 @@ static inline int vpci_assign_device(struct domain *d, struct pci_dev *pdev)
 static inline void vpci_deassign_device(struct domain *d, struct pci_dev *pdev)
 {
 };
+
+static inline bool vpci_translate_virtual_device(const struct domain *d,
+                                                 pci_sbdf_t *sbdf)
+{
+    return false;
+}
 #endif
 
 #endif
-- 
2.25.1