Extend set_sregs_test to cover CR8. Verify that the architecturally allowed bits [3:0] can be set and read back, that every reserved bit [63:4] is rejected by KVM_SET_SREGS, and that a successful set is observable via KVM_GET_SREGS.
Without the accompanying fix to kvm_is_valid_sregs(), setting a reserved CR8 bit is silently accepted and the read-back value diverges from the value written, so this test fails on an unpatched kernel and passes once the fix is applied. Signed-off-by: Tharit Tangkijwanichakul <[email protected]> --- tools/testing/selftests/kvm/x86/set_sregs_test.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/tools/testing/selftests/kvm/x86/set_sregs_test.c b/tools/testing/selftests/kvm/x86/set_sregs_test.c index 603226ffe437..4e7c35179438 100644 --- a/tools/testing/selftests/kvm/x86/set_sregs_test.c +++ b/tools/testing/selftests/kvm/x86/set_sregs_test.c @@ -135,6 +135,18 @@ static void test_cr_bits(struct kvm_vcpu *vcpu, u64 cr4) /* NW without CD is illegal, as is PG without PE. */ TEST_INVALID_SREG_BIT(vcpu, cr0, sregs, X86_CR0_NW); TEST_INVALID_SREG_BIT(vcpu, cr0, sregs, X86_CR0_PG); + + /* CR8 bits 3:0 are writable; bits 63:4 are reserved. */ + vcpu_sregs_get(vcpu, &sregs); + sregs.cr8 = 0xf; + rc = _vcpu_sregs_set(vcpu, &sregs); + TEST_ASSERT(!rc, "Failed to set valid CR8 value 0xf"); + + vcpu_sregs_get(vcpu, &sregs); + TEST_ASSERT_EQ(sregs.cr8, 0xf); + + for (i = 4; i < 64; i++) + TEST_INVALID_SREG_BIT(vcpu, cr8, sregs, BIT_ULL(i)); } static void test_efer_bits(struct kvm_vcpu *vcpu, u64 efer) -- 2.53.0
