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authorPaolo Bonzini <pbonzini@redhat.com>2022-12-12 05:36:53 -0500
committerPaolo Bonzini <pbonzini@redhat.com>2022-12-27 06:00:49 -0500
commitfeb84f6daa7e7d51444d13fa65df7d5562fd0075 (patch)
tree7641ca1f30e36e72f660c62f2d296f48b0dec054 /tools
parent2f5213b8fc311eaa8fc78de7ecbd27ead027993c (diff)
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KVM: selftests: document the default implementation of vm_vaddr_populate_bitmap
Explain the meaning of the bit manipulations of vm_vaddr_populate_bitmap. These correspond to the "canonical addresses" of x86 and other architectures, but that is not obvious. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'tools')
-rw-r--r--tools/testing/selftests/kvm/lib/kvm_util.c9
1 files changed, 9 insertions, 0 deletions
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index c88c3ace16d2..bd892a814951 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -186,6 +186,15 @@ const struct vm_guest_mode_params vm_guest_mode_params[] = {
_Static_assert(sizeof(vm_guest_mode_params)/sizeof(struct vm_guest_mode_params) == NUM_VM_MODES,
"Missing new mode params?");
+/*
+ * Initializes vm->vpages_valid to match the canonical VA space of the
+ * architecture.
+ *
+ * The default implementation is valid for architectures which split the
+ * range addressed by a single page table into a low and high region
+ * based on the MSB of the VA. On architectures with this behavior
+ * the VA region spans [0, 2^(va_bits - 1)), [-(2^(va_bits - 1), -1].
+ */
__weak void vm_vaddr_populate_bitmap(struct kvm_vm *vm)
{
sparsebit_set_num(vm->vpages_valid,