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-rw-r--r--drivers/lguest/page_tables.c18
1 files changed, 11 insertions, 7 deletions
diff --git a/drivers/lguest/page_tables.c b/drivers/lguest/page_tables.c
index a2454a24a10c..27cbb186a911 100644
--- a/drivers/lguest/page_tables.c
+++ b/drivers/lguest/page_tables.c
@@ -63,10 +63,8 @@
*/
#ifdef CONFIG_X86_PAE
#define SWITCHER_PMD_INDEX (PTRS_PER_PMD - 1)
-#define RESERVE_MEM 2U
#define CHECK_GPGD_MASK _PAGE_PRESENT
#else
-#define RESERVE_MEM 4U
#define CHECK_GPGD_MASK _PAGE_TABLE
#endif
@@ -977,15 +975,21 @@ int init_guest_pagetable(struct lguest *lg)
/*H:508 When the Guest calls LHCALL_LGUEST_INIT we do more setup. */
void page_table_guest_data_init(struct lg_cpu *cpu)
{
+ /*
+ * We tell the Guest that it can't use the virtual addresses
+ * used by the Switcher. This trick is equivalent to 4GB -
+ * switcher_addr.
+ */
+ u32 top = ~switcher_addr + 1;
+
/* We get the kernel address: above this is all kernel memory. */
if (get_user(cpu->lg->kernel_address,
- &cpu->lg->lguest_data->kernel_address)
+ &cpu->lg->lguest_data->kernel_address)
/*
- * We tell the Guest that it can't use the top 2 or 4 MB
- * of virtual addresses used by the Switcher.
+ * We tell the Guest that it can't use the top virtual
+ * addresses (used by the Switcher).
*/
- || put_user(RESERVE_MEM * 1024 * 1024,
- &cpu->lg->lguest_data->reserve_mem)) {
+ || put_user(top, &cpu->lg->lguest_data->reserve_mem)) {
kill_guest(cpu, "bad guest page %p", cpu->lg->lguest_data);
return;
}