[PATCH v2 2/4] xen/pci: Introduce new CONFIG_PCI_ATS flag for PCI ATS functionality.

[Rahul Singh <rahul.singh@xxxxxxx>]

PCI ATS functionality is not enabled and tested for ARM architecture
but it is enabled for x86 and referenced in common passthrough/pci.c
code.

Therefore introducing the new flag to enable the ATS functionality for
x86 only to avoid issues for ARM architecture.

No functional change.

Signed-off-by: Rahul Singh <rahul.singh@xxxxxxx>
---

Changes in v2:
 - Fixed return value of PCI ATS related functions when PCI_ATS is not enabled.
 - Make PCI_ATS user selectable kconfig option.

---
 xen/drivers/passthrough/ats.h        | 26 ++++++++++++++++++++++++++
 xen/drivers/passthrough/x86/Makefile |  2 +-
 xen/drivers/pci/Kconfig              |  9 +++++++++
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/xen/drivers/passthrough/ats.h b/xen/drivers/passthrough/ats.h
index 22ae209b37..3a71fedcb4 100644
--- a/xen/drivers/passthrough/ats.h
+++ b/xen/drivers/passthrough/ats.h
@@ -17,6 +17,8 @@
 
 #include <xen/pci_regs.h>
 
+#ifdef CONFIG_PCI_ATS
+
 #define ATS_REG_CAP    4
 #define ATS_REG_CTL    6
 #define ATS_QUEUE_DEPTH_MASK     0x1f
@@ -48,5 +50,29 @@ static inline int pci_ats_device(int seg, int bus, int devfn)
     return pci_find_ext_capability(seg, bus, devfn, PCI_EXT_CAP_ID_ATS);
 }
 
+#else
+
+#define ats_enabled (false)
+
+static inline int enable_ats_device(struct pci_dev *pdev,
+                                    struct list_head *ats_list)
+{
+    return -EOPNOTSUPP;
+}
+
+static inline void disable_ats_device(struct pci_dev *pdev) { }
+
+static inline int pci_ats_enabled(int seg, int bus, int devfn)
+{
+    return 0;
+}
+
+static inline int pci_ats_device(int seg, int bus, int devfn)
+{
+    return 0;
+}
+
+#endif /* CONFIG_PCI_ATS */
+
 #endif /* _ATS_H_ */
 
diff --git a/xen/drivers/passthrough/x86/Makefile 
b/xen/drivers/passthrough/x86/Makefile
index a70cf9460d..aa515c680d 100644
--- a/xen/drivers/passthrough/x86/Makefile
+++ b/xen/drivers/passthrough/x86/Makefile
@@ -1,2 +1,2 @@
-obj-y += ats.o
+obj-$(CONFIG_PCI_ATS) += ats.o
 obj-y += iommu.o
diff --git a/xen/drivers/pci/Kconfig b/xen/drivers/pci/Kconfig
index 7da03fa13b..3cb79ea954 100644
--- a/xen/drivers/pci/Kconfig
+++ b/xen/drivers/pci/Kconfig
@@ -1,3 +1,12 @@
 
 config HAS_PCI
        bool
+
+config PCI_ATS
+       bool "PCI ATS support"
+       default y
+       depends on X86 && HAS_PCI
+       ---help---
+        Enable PCI Address Translation Services.
+
+        If unsure, say Y.
-- 
2.17.1