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xen/balloon: Mark unallocated host memory as UNUSABLE

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Commit f5775e0b61 ("x86/xen: discard RAM regions above the maximum
reservation") left host memory not assigned to dom0 as available for
memory hotplug.

Unfortunately this also meant that those regions could be used by
others. Specifically, commit fa564ad963 ("x86/PCI: Enable a 64bit BAR
on AMD Family 15h (Models 00-1f, 30-3f, 60-7f)") may try to map those
addresses as MMIO.

To prevent this mark unallocated host memory as E820_TYPE_UNUSABLE (thus
effectively reverting f5775e0b61) and keep track of that region as
a hostmem resource that can be used for the hotplug.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Boris Ostrovsky
2017-12-12 15:08:21 -05:00
parent 2cc42bac1c
commit b3cf8528bb
4 changed files with 144 additions and 13 deletions
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81
arch/x86/xen/enlighten.c
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@@ -1,8 +1,12 @@
#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
#include <linux/bootmem.h>
#endif
#include <linux/cpu.h>
#include <linux/kexec.h>
#include <xen/features.h>
#include <xen/page.h>
#include <xen/interface/memory.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
@@ -331,3 +335,80 @@ 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 */