x86, vmi: Disable highmem PTE allocation even when CONFIG_HIGHPTE=y

Preventing HIGHPTE allocations under VMI will allow us to remove the
kmap_atomic_pte paravirt op.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
LKML-Reference: <1267204562-11844-2-git-send-email-ian.campbell@citrix.com>
Acked-by: Alok Kataria <akataria@vmware.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

1 files changed, 11 insertions, 12 deletions

diff --git a/arch/x86/kernel/vmi_32.c b/arch/x86/kernel/vmi_32.c
index d430e4c30193..58aca86193e5 100644
--- a/arch/x86/kernel/vmi_32.c
+++ b/arch/x86/kernel/vmi_32.c
@@ -33,6 +33,7 @@
 #include <asm/fixmap.h>
 #include <asm/apicdef.h>
 #include <asm/apic.h>
+#include <asm/pgalloc.h>
 #include <asm/processor.h>
 #include <asm/timer.h>
 #include <asm/vmi_time.h>
@@ -272,19 +273,11 @@ static void *vmi_kmap_atomic_pte(struct page *page, enum km_type type)
         void *va = kmap_atomic(page, type);
 
         /*
-         * Internally, the VMI ROM must map virtual addresses to physical
-         * addresses for processing MMU updates.  By the time MMU updates
-         * are issued, this information is typically already lost.
-         * Fortunately, the VMI provides a cache of mapping slots for active
-         * page tables.
-         *
-         * We use slot zero for the linear mapping of physical memory, and
-         * in HIGHPTE kernels, slot 1 and 2 for KM_PTE0 and KM_PTE1.
-         *
-         *  args:                 SLOT                 VA    COUNT PFN
+         * We disable highmem allocations for page tables so we should never
+         * see any calls to kmap_atomic_pte on a highmem page.
          */
-        BUG_ON(type != KM_PTE0 && type != KM_PTE1);
-        vmi_ops.set_linear_mapping((type - KM_PTE0)+1, va, 1, page_to_pfn(page));
+
+        BUG_ON(PageHighmem(page));
 
         return va;
 }
@@ -640,6 +633,12 @@ static inline int __init activate_vmi(void)
         u64 reloc;
         const struct vmi_relocation_info *rel = (struct vmi_relocation_info *)&reloc;
 
+        /*
+         * Prevent page tables from being allocated in highmem, even if
+         * CONFIG_HIGHPTE is enabled.
+         */
+        __userpte_alloc_gfp &= ~__GFP_HIGHMEM;
+
         if (call_vrom_func(vmi_rom, vmi_init) != 0) {
                 printk(KERN_ERR "VMI ROM failed to initialize!");
                 return 0;