[PATCH 1/3] xen/pci: add flag for PCI passthrough being possible

[Christoph Hellwig <hch@xxxxxx>]

From: Juergen Gross <jgross@xxxxxxxx>

When running as a Xen PV guests passed through PCI devices only have a
chance to work if the Xen supplied memory map has some PCI space
reserved.

Add a flag xen_pv_pci_possible which will be set in early boot in case
the memory map has at least one area with the type E820_TYPE_RESERVED.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 arch/x86/xen/setup.c | 6 ++++++
 include/xen/xen.h    | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index c2be3efb2ba0fa..716f76c4141651 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -43,6 +43,9 @@ struct xen_memory_region 
xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
 /* Number of pages released from the initial allocation. */
 unsigned long xen_released_pages;
 
+/* Memory map would allow PCI passthrough. */
+bool xen_pv_pci_possible;
+
 /* E820 map used during setting up memory. */
 static struct e820_table xen_e820_table __initdata;
 
@@ -804,6 +807,9 @@ char * __init xen_memory_setup(void)
                chunk_size = size;
                type = xen_e820_table.entries[i].type;
 
+               if (type == E820_TYPE_RESERVED)
+                       xen_pv_pci_possible = true;
+
                if (type == E820_TYPE_RAM) {
                        if (addr < mem_end) {
                                chunk_size = min(size, mem_end - addr);
diff --git a/include/xen/xen.h b/include/xen/xen.h
index 0efeb652f9b8fb..5eb0a974a11e7e 100644
--- a/include/xen/xen.h
+++ b/include/xen/xen.h
@@ -29,6 +29,12 @@ extern bool xen_pvh;
 
 extern uint32_t xen_start_flags;
 
+#ifdef CONFIG_XEN_PV
+extern bool xen_pv_pci_possible;
+#else
+#define xen_pv_pci_possible    0
+#endif
+
 #include <xen/interface/hvm/start_info.h>
 extern struct hvm_start_info pvh_start_info;
 
-- 
2.39.2