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-rw-r--r--arch/x86/xen/enlighten_pvh.c68
1 files changed, 68 insertions, 0 deletions
diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
index ada3868c02..c28f073c1d 100644
--- a/arch/x86/xen/enlighten_pvh.c
+++ b/arch/x86/xen/enlighten_pvh.c
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0
#include <linux/acpi.h>
#include <linux/export.h>
+#include <linux/mm.h>
#include <xen/hvc-console.h>
@@ -72,3 +73,70 @@ void __init mem_map_via_hcall(struct boot_params *boot_params_p)
}
boot_params_p->e820_entries = memmap.nr_entries;
}
+
+/*
+ * Reserve e820 UNUSABLE regions to inflate the memory balloon.
+ *
+ * On PVH dom0 the host memory map is used, RAM regions available to dom0 are
+ * located as the same place as in the native memory map, but since dom0 gets
+ * less memory than the total amount of host RAM the ranges that can't be
+ * populated are converted from RAM -> UNUSABLE. Use such regions (up to the
+ * ratio signaled in EXTRA_MEM_RATIO) in order to inflate the balloon driver at
+ * boot. Doing so prevents the guest (even if just temporary) from using holes
+ * in the memory map in order to map grants or foreign addresses, and
+ * hopefully limits the risk of a clash with a device MMIO region. Ideally the
+ * hypervisor should notify us which memory ranges are suitable for creating
+ * foreign mappings, but that's not yet implemented.
+ */
+void __init xen_reserve_extra_memory(struct boot_params *bootp)
+{
+ unsigned int i, ram_pages = 0, extra_pages;
+
+ for (i = 0; i < bootp->e820_entries; i++) {
+ struct boot_e820_entry *e = &bootp->e820_table[i];
+
+ if (e->type != E820_TYPE_RAM)
+ continue;
+ ram_pages += PFN_DOWN(e->addr + e->size) - PFN_UP(e->addr);
+ }
+
+ /* Max amount of extra memory. */
+ extra_pages = EXTRA_MEM_RATIO * ram_pages;
+
+ /*
+ * Convert UNUSABLE ranges to RAM and reserve them for foreign mapping
+ * purposes.
+ */
+ for (i = 0; i < bootp->e820_entries && extra_pages; i++) {
+ struct boot_e820_entry *e = &bootp->e820_table[i];
+ unsigned long pages;
+
+ if (e->type != E820_TYPE_UNUSABLE)
+ continue;
+
+ pages = min(extra_pages,
+ PFN_DOWN(e->addr + e->size) - PFN_UP(e->addr));
+
+ if (pages != (PFN_DOWN(e->addr + e->size) - PFN_UP(e->addr))) {
+ struct boot_e820_entry *next;
+
+ if (bootp->e820_entries ==
+ ARRAY_SIZE(bootp->e820_table))
+ /* No space left to split - skip region. */
+ continue;
+
+ /* Split entry. */
+ next = e + 1;
+ memmove(next, e,
+ (bootp->e820_entries - i) * sizeof(*e));
+ bootp->e820_entries++;
+ next->addr = PAGE_ALIGN(e->addr) + PFN_PHYS(pages);
+ e->size = next->addr - e->addr;
+ next->size -= e->size;
+ }
+ e->type = E820_TYPE_RAM;
+ extra_pages -= pages;
+
+ xen_add_extra_mem(PFN_UP(e->addr), pages);
+ }
+}