xen/pvh: Update E820 to work with PVH (v2)

In xen_add_extra_mem() we can skip updating P2M as it's managed
by Xen. PVH maps the entire IO space, but only RAM pages need
to be repopulated.
Signed-off-by: Mukesh Rathor <mukesh.rathor@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

arch/x86/xen/setup.c

@@ -27,6 +27,7 @@
 #include <xen/interface/memory.h>
 #include <xen/interface/physdev.h>
 #include <xen/features.h>
+#include "mmu.h"
 #include "xen-ops.h"
 #include "vdso.h"
 
@@ -81,6 +82,9 @@ static void __init xen_add_extra_mem(u64 start, u64 size)
 
 	memblock_reserve(start, size);
 
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return;
+
 	xen_max_p2m_pfn = PFN_DOWN(start + size);
 	for (pfn = PFN_DOWN(start); pfn < xen_max_p2m_pfn; pfn++) {
 		unsigned long mfn = pfn_to_mfn(pfn);
@@ -103,6 +107,7 @@ static unsigned long __init xen_do_chunk(unsigned long start,
 		.domid        = DOMID_SELF
 	};
 	unsigned long len = 0;
+	int xlated_phys = xen_feature(XENFEAT_auto_translated_physmap);
 	unsigned long pfn;
 	int ret;
 
@@ -116,7 +121,7 @@ static unsigned long __init xen_do_chunk(unsigned long start,
 				continue;
 			frame = mfn;
 		} else {
-			if (mfn != INVALID_P2M_ENTRY)
+			if (!xlated_phys && mfn != INVALID_P2M_ENTRY)
 				continue;
 			frame = pfn;
 		}
@@ -154,6 +159,13 @@ static unsigned long __init xen_do_chunk(unsigned long start,
 static unsigned long __init xen_release_chunk(unsigned long start,
 					      unsigned long end)
 {
+	/*
+	 * Xen already ballooned out the E820 non RAM regions for us
+	 * and set them up properly in EPT.
+	 */
+	if (xen_feature(XENFEAT_auto_translated_physmap))
+		return end - start;
+
 	return xen_do_chunk(start, end, true);
 }
 
@@ -222,7 +234,13 @@ static void __init xen_set_identity_and_release_chunk(
 	 * (except for the ISA region which must be 1:1 mapped) to
 	 * release the refcounts (in Xen) on the original frames.
 	 */
-	for (pfn = start_pfn; pfn <= max_pfn_mapped && pfn < end_pfn; pfn++) {
+
+	/*
+	 * PVH E820 matches the hypervisor's P2M which means we need to
+	 * account for the proper values of *release and *identity.
+	 */
+	for (pfn = start_pfn; !xen_feature(XENFEAT_auto_translated_physmap) &&
+	     pfn <= max_pfn_mapped && pfn < end_pfn; pfn++) {
 		pte_t pte = __pte_ma(0);
 
 		if (pfn < PFN_UP(ISA_END_ADDRESS))