KVM: selftests: Fix off-by-one initialization of GDT limit

Fix an off-by-one bug in the initialization of the GDT limit, which as
defined in the SDM is inclusive, not exclusive.

Note, vcpu_init_descriptor_tables() gets the limit correct, it's only
vcpu_setup() that is broken, i.e. only tests that _don't_ invoke
vcpu_init_descriptor_tables() can have problems.  And the fact that KVM
effectively initializes the GDT twice will be cleaned up in the near
future.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
[sean: rewrite changelog]
Link: https://lore.kernel.org/r/20240314232637.2538648-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index f2506b9edb37d7ec7848a6b7abb87032cab9ca78..a04c2e623d099058c88c837aaa8558bb39d6b6bd 100644 (file)
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -523,7 +523,7 @@ static void kvm_setup_gdt(struct kvm_vm *vm, struct kvm_dtable *dt)
                vm->arch.gdt = __vm_vaddr_alloc_page(vm, MEM_REGION_DATA);
 
        dt->base = vm->arch.gdt;
-       dt->limit = getpagesize();
+       dt->limit = getpagesize() - 1;
 }
 
 static void kvm_setup_tss_64bit(struct kvm_vm *vm, struct kvm_segment *segp,