kvm: selftests: ucall: improve ucall placement in memory, fix unsigned comparison

Based on a patch by Andrew Jones.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/tools/testing/selftests/kvm/lib/ucall.c b/tools/testing/selftests/kvm/lib/ucall.c
index 4777f9bb5194baa321ba67f56006111375a66148..694bc2eaa63e9f8661024916e591b7a51e5cc342 100644 (file)
--- a/tools/testing/selftests/kvm/lib/ucall.c
+++ b/tools/testing/selftests/kvm/lib/ucall.c
@@ -34,7 +34,7 @@ void ucall_init(struct kvm_vm *vm, ucall_type_t type, void *arg)
                return;
 
        if (type == UCALL_MMIO) {
-               vm_paddr_t gpa, start, end, step;
+               vm_paddr_t gpa, start, end, step, offset;
                bool ret;
 
                if (arg) {
@@ -53,17 +53,15 @@ void ucall_init(struct kvm_vm *vm, ucall_type_t type, void *arg)
                 * KVM_EXIT_MMIO. Well, at least that's how it works for AArch64.
                 * Here we start with a guess that the addresses around two
                 * thirds of the VA space are unmapped and then work both down
-                * and up from there in 1/6 VA space sized steps.
+                * and up from there in 1/12 VA space sized steps.
                 */
                start = 1ul << (vm->va_bits * 2 / 3);
                end = 1ul << vm->va_bits;
-               step = 1ul << (vm->va_bits / 6);
-               for (gpa = start; gpa >= 0; gpa -= step) {
-                       if (ucall_mmio_init(vm, gpa & ~(vm->page_size - 1)))
+               step = 1ul << (vm->va_bits / 12);
+               for (offset = 0; offset < end - start; offset += step) {
+                       if (ucall_mmio_init(vm, (gpa - offset) & ~(vm->page_size - 1)))
                                return;
-               }
-               for (gpa = start + step; gpa < end; gpa += step) {
-                       if (ucall_mmio_init(vm, gpa & ~(vm->page_size - 1)))
+                       if (ucall_mmio_init(vm, (gpa + offset) & ~(vm->page_size - 1)))
                                return;
                }
                TEST_ASSERT(false, "Can't find a ucall mmio address");