xen/arm: pci: Add stubs to allow selecting HAS_PCI

In a follow-up we will enable PCI support in Xen on Arm (i.e select
HAS_PCI).

The generic code expects the arch to implement a few functions:
arch_iommu_use_permitted()
arch_pci_clean_pirqs()

Note that this is not yet sufficient to enable HAS_PCI and will be
addressed in follow-ups.

Signed-off-by: Rahul Singh <rahul.singh@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Reviewed-by: Bertrand Marquis <bertrand.marquis@arm.com>

xen/arch/arm/Makefile

@@ -2,6 +2,7 @@ obj-$(CONFIG_ARM_32) += arm32/
 obj-$(CONFIG_ARM_64) += arm64/
 obj-$(CONFIG_ARM_64) += efi/
 obj-$(CONFIG_ACPI) += acpi/
+obj-$(CONFIG_HAS_PCI) += pci/
 ifneq ($(CONFIG_NO_PLAT),y)
 obj-y += platforms/
 endif

xen/arch/arm/pci/Makefile

@@ -0,0 +1 @@
+obj-y += pci.o

xen/arch/arm/pci/pci.c

@@ -0,0 +1,33 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <xen/pci.h>
+
+/*
+ * PIRQ event channels are not supported on Arm, so nothing to do.
+ */
+int arch_pci_clean_pirqs(struct domain *d)
+{
+    return 0;
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */

xen/drivers/passthrough/arm/iommu.c

@@ -135,3 +135,12 @@ void arch_iommu_domain_destroy(struct domain *d)
 void __hwdom_init arch_iommu_hwdom_init(struct domain *d)
 {
 }
+
+/*
+ * Unlike x86, Arm doesn't support mem-sharing, mem-paging and log-dirty (yet).
+ * So there is no restriction to use the IOMMU.
+ */
+bool arch_iommu_use_permitted(const struct domain *d)
+{
+    return true;
+}

xen/include/asm-arm/pci.h

@@ -1,7 +1,32 @@
-#ifndef __X86_PCI_H__
-#define __X86_PCI_H__
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
 
+#ifndef __ARM_PCI_H__
+#define __ARM_PCI_H__
+
+#ifdef CONFIG_HAS_PCI
+
+#define pci_to_dev(pcidev) (&(pcidev)->arch.dev)
+
+/* Arch pci dev struct */
 struct arch_pci_dev {
+    struct device dev;
 };
 
-#endif /* __X86_PCI_H__ */
+#else   /*!CONFIG_HAS_PCI*/
+
+struct arch_pci_dev { };
+
+#endif  /*!CONFIG_HAS_PCI*/
+#endif /* __ARM_PCI_H__ */