Revert "xen/balloon: Mark unallocated host memory as UNUSABLE"

[ Upstream commit 123664101aa2156d05251704fc63f9bcbf77741a ]

This reverts commit b3cf8528bb21febb650a7ecbf080d0647be40b9f.

That commit unintentionally broke Xen balloon memory hotplug with
"hotplug_unpopulated" set to 1. As long as "System RAM" resource
got assigned under a new "Unusable memory" resource in IO/Mem tree
any attempt to online this memory would fail due to general kernel
restrictions on having "System RAM" resources as 1st level only.

The original issue that commit has tried to workaround fa564ad96366
("x86/PCI: Enable a 64bit BAR on AMD Family 15h (Models 00-1f, 30-3f,
60-7f)") also got amended by the following 03a551734 ("x86/PCI: Move
and shrink AMD 64-bit window to avoid conflict") which made the
original fix to Xen ballooning unnecessary.

Signed-off-by: Igor Druzhinin <igor.druzhinin@citrix.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

2 files changed, 4 insertions, 80 deletions

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 2eeddd814653..c6c7c9b7b5c1 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -7,7 +7,6 @@
 
 #include <xen/features.h>
 #include <xen/page.h>
-#include <xen/interface/memory.h>
 
 #include <asm/xen/hypercall.h>
 #include <asm/xen/hypervisor.h>
@@ -343,80 +342,3 @@ void xen_arch_unregister_cpu(int num)
 }
 EXPORT_SYMBOL(xen_arch_unregister_cpu);
 #endif
-
-#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
-void __init arch_xen_balloon_init(struct resource *hostmem_resource)
-{
-	struct xen_memory_map memmap;
-	int rc;
-	unsigned int i, last_guest_ram;
-	phys_addr_t max_addr = PFN_PHYS(max_pfn);
-	struct e820_table *xen_e820_table;
-	const struct e820_entry *entry;
-	struct resource *res;
-
-	if (!xen_initial_domain())
-		return;
-
-	xen_e820_table = kmalloc(sizeof(*xen_e820_table), GFP_KERNEL);
-	if (!xen_e820_table)
-		return;
-
-	memmap.nr_entries = ARRAY_SIZE(xen_e820_table->entries);
-	set_xen_guest_handle(memmap.buffer, xen_e820_table->entries);
-	rc = HYPERVISOR_memory_op(XENMEM_machine_memory_map, &memmap);
-	if (rc) {
-		pr_warn("%s: Can't read host e820 (%d)\n", __func__, rc);
-		goto out;
-	}
-
-	last_guest_ram = 0;
-	for (i = 0; i < memmap.nr_entries; i++) {
-		if (xen_e820_table->entries[i].addr >= max_addr)
-			break;
-		if (xen_e820_table->entries[i].type == E820_TYPE_RAM)
-			last_guest_ram = i;
-	}
-
-	entry = &xen_e820_table->entries[last_guest_ram];
-	if (max_addr >= entry->addr + entry->size)
-		goto out; /* No unallocated host RAM. */
-
-	hostmem_resource->start = max_addr;
-	hostmem_resource->end = entry->addr + entry->size;
-
-	/*
-	 * Mark non-RAM regions between the end of dom0 RAM and end of host RAM
-	 * as unavailable. The rest of that region can be used for hotplug-based
-	 * ballooning.
-	 */
-	for (; i < memmap.nr_entries; i++) {
-		entry = &xen_e820_table->entries[i];
-
-		if (entry->type == E820_TYPE_RAM)
-			continue;
-
-		if (entry->addr >= hostmem_resource->end)
-			break;
-
-		res = kzalloc(sizeof(*res), GFP_KERNEL);
-		if (!res)
-			goto out;
-
-		res->name = "Unavailable host RAM";
-		res->start = entry->addr;
-		res->end = (entry->addr + entry->size < hostmem_resource->end) ?
-			    entry->addr + entry->size : hostmem_resource->end;
-		rc = insert_resource(hostmem_resource, res);
-		if (rc) {
-			pr_warn("%s: Can't insert [%llx - %llx) (%d)\n",
-				__func__, res->start, res->end, rc);
-			kfree(res);
-			goto  out;
-		}
-	}
-
- out:
-	kfree(xen_e820_table);
-}
-#endif /* CONFIG_XEN_BALLOON_MEMORY_HOTPLUG */
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 1163e33121fb..075ed47993bb 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -808,6 +808,7 @@ char * __init xen_memory_setup(void)
 	addr = xen_e820_table.entries[0].addr;
 	size = xen_e820_table.entries[0].size;
 	while (i < xen_e820_table.nr_entries) {
+		bool discard = false;
 
 		chunk_size = size;
 		type = xen_e820_table.entries[i].type;
@@ -823,10 +824,11 @@ char * __init xen_memory_setup(void)
 				xen_add_extra_mem(pfn_s, n_pfns);
 				xen_max_p2m_pfn = pfn_s + n_pfns;
 			} else
-				type = E820_TYPE_UNUSABLE;
+				discard = true;
 		}
 
-		xen_align_and_add_e820_region(addr, chunk_size, type);
+		if (!discard)
+			xen_align_and_add_e820_region(addr, chunk_size, type);
 
 		addr += chunk_size;
 		size -= chunk_size;