[PATCH 1/2] KVM: selftests: Fix initialization of GDT limit

From: Ackerley Tng <ackerleytng@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
	Shuah Khan <shuah@kernel.org>,
	Sean Christopherson <seanjc@google.com>,
	David Matlack <dmatlack@google.com>,
	Wei Wang <wei.w.wang@intel.com>
Cc: kvm@vger.kernel.org, linux-kselftest@vger.kernel.org,
	Ackerley Tng <ackerleytng@google.com>
Subject: [PATCH 1/2] KVM: selftests: Fix initialization of GDT limit
Date: Sat, 14 Jan 2023 16:15:56 +0000	[thread overview]
Message-ID: <20230114161557.499685-2-ackerleytng@google.com> (raw)
In-Reply-To: <20230114161557.499685-1-ackerleytng@google.com>

Subtract 1 to initialize GDT limit according to spec.

Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
 tools/testing/selftests/kvm/lib/x86_64/processor.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index acfa1d01e7df..33ca7f5232a4 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -502,7 +502,12 @@ static void kvm_setup_gdt(struct kvm_vm *vm, struct kvm_dtable *dt)
 		vm->gdt = __vm_vaddr_alloc_page(vm, MEM_REGION_DATA);
 
 	dt->base = vm->gdt;
-	dt->limit = getpagesize();
+
+	/*
+	 * Intel SDM Volume 3, 3.5.1: "the GDT limit should always be one less
+	 * than an integral multiple of eight"
+	 */
+	dt->limit = getpagesize() - 1;
 }
 
 static void kvm_setup_tss_64bit(struct kvm_vm *vm, struct kvm_segment *segp,
-- 
2.39.0.314.g84b9a713c41-goog

