arm/arm64: KVM: Check that IDMAP doesn't intersect with VA range

This is more of a safety measure than anything else: If we end-up
with an idmap page that intersect with the range picked for the
the HYP VA space, abort the KVM setup, as it is unsafe to go
further.

I cannot imagine it happening on 64bit (we have a mechanism to
work around it), but could potentially occur on a 32bit system with
the kernel loaded high enough in memory so that in conflicts with
the kernel VA.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 0b36dd52af62..8a0aa37605c5 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1709,6 +1709,21 @@ int kvm_mmu_init(void)
          */
         BUG_ON((hyp_idmap_start ^ (hyp_idmap_end - 1)) & PAGE_MASK);
 
+        kvm_info("IDMAP page: %lx\n", hyp_idmap_start);
+        kvm_info("HYP VA range: %lx:%lx\n",
+                 KERN_TO_HYP(PAGE_OFFSET), KERN_TO_HYP(~0UL));
+
+        if (hyp_idmap_start >= KERN_TO_HYP(PAGE_OFFSET) &&
+            hyp_idmap_start <  KERN_TO_HYP(~0UL)) {
+                /*
+                 * The idmap page is intersecting with the VA space,
+                 * it is not safe to continue further.
+                 */
+                kvm_err("IDMAP intersecting with HYP VA, unable to continue\n");
+                err = -EINVAL;
+                goto out;
+        }
+
         hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, hyp_pgd_order);
         if (!hyp_pgd) {
                 kvm_err("Hyp mode PGD not allocated\n");