linux-kernel - [PATCH 04/18] KVM: selftests: Fix off-by-one initialization of GDT limit

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Date: Thu, 14 Mar 2024 16:26:23 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Paolo Bonzini <pbonzini@...hat.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Janosch Frank <frankja@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>, 
	Sean Christopherson <seanjc@...gle.com>, Anup Patel <anup@...infault.org>, 
	Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, 
	Albert Ou <aou@...s.berkeley.edu>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
	kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Ackerley Tng <ackerleytng@...gle.com>
Subject: [PATCH 04/18] KVM: selftests: Fix off-by-one initialization of GDT limit

From: Ackerley Tng <ackerleytng@...gle.com>

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@...gle.com>
[sean: rewrite changelog]
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 tools/testing/selftests/kvm/lib/x86_64/processor.c | 2 +-
 1 file changed, 1 insertion(+), 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 45f965c052a1..eaeba907bb53 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -522,7 +522,7 @@ 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,
-- 
2.44.0.291.gc1ea87d7ee-goog