Re: [PATCH 2/2] KVM: selftests: Add test for nested VM-Exits while vectoring soft INTs

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] KVM: selftests: standalone test duplicates nested_exceptions_test setup
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commit 419533e2e5a5342a3cc80d072a4cecd9f800a093
Author: Mahmoud Abumandour <ma.mandourr@gmail.com>

KVM: selftests: Add test for nested VM-Exits while vectoring soft INTs

This commit adds a standalone KVM x86 selftest to verify that a nested
VM-Exit occurring while L2 vectors a software exception or interrupt reports
the instruction length in VM_EXIT_INSTRUCTION_LEN without modifying
VM_ENTRY_INSTRUCTION_LEN.

> diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
> index 888a7530a2808..d5f8749413f27 100644
> --- a/tools/testing/selftests/kvm/Makefile.kvm
> +++ b/tools/testing/selftests/kvm/Makefile.kvm
> @@ -140,6 +140,7 @@ TEST_GEN_PROGS_x86 += x86/vmx_exception_with_invalid_guest_state
>  TEST_GEN_PROGS_x86 += x86/vmx_msrs_test
>  TEST_GEN_PROGS_x86 += x86/vmx_invalid_nested_guest_state
>  TEST_GEN_PROGS_x86 += x86/vmx_nested_la57_state_test
> +TEST_GEN_PROGS_x86 += x86/vmx_soft_int_vectoring_test
>  TEST_GEN_PROGS_x86 += x86/apic_bus_clock_test
>  TEST_GEN_PROGS_x86 += x86/xapic_ipi_test
>  TEST_GEN_PROGS_x86 += x86/xapic_state_test
> diff --git a/tools/testing/selftests/kvm/x86/vmx_soft_int_vectoring_test.c b/tools/testing/selftests/kvm/x86/vmx_soft_int_vectoring_test.c
> new file mode 100644
> index 0000000000000..e74510c49938c
> --- /dev/null
> +++ b/tools/testing/selftests/kvm/x86/vmx_soft_int_vectoring_test.c

[ ... ]

> +static void l1_guest_code(struct vmx_pages *vmx_pages)
> +{
> +	prepare_for_vmx_operation(vmx_pages);
> +	load_vmcs(vmx_pages);
> +	prepare_vmcs(vmx_pages, l2_guest_code);
> +
> +	/*
> +	 * Put every IDT entry beyond the limit so that vectoring any event in
> +	 * L2 generates #GP, and intercept #GP so that the VM-Exit occurs while
> +	 * the original event is being vectored.
> +	 */
> +	vmwrite(GUEST_IDTR_LIMIT, 0);
> +	vmwrite(EXCEPTION_BITMAP, BIT(GP_VECTOR));
> +	vmwrite(VM_ENTRY_INSTRUCTION_LEN, ENTRY_INSN_LEN);
> +
> +	vmlaunch();
> +	l1_assert_vectoring_exit("INT3", INTR_TYPE_SOFT_EXCEPTION | BP_VECTOR, 1);
> +
> +	vmresume();
> +	l1_assert_vectoring_exit("INTn", INTR_TYPE_SOFT_INTR | SOFT_INT_VECTOR, 2);
> +
> +	vmresume();
> +	GUEST_ASSERT_EQ(vmread(VM_EXIT_REASON), EXIT_REASON_VMCALL);
> +	GUEST_DONE();
> +}

[Severity: Medium]
This isn't a bug, but l1_guest_code() in
tools/testing/selftests/kvm/x86/vmx_soft_int_vectoring_test.c duplicates the
nested VMCS setup, empty GUEST_IDTR_LIMIT configuration, and GP_VECTOR
interception in EXCEPTION_BITMAP that l1_vmx_code() in
tools/testing/selftests/kvm/x86/nested_exceptions_test.c already sets up to
trigger nested VM-Exits during L2 event vectoring:

tools/testing/selftests/kvm/x86/nested_exceptions_test.c:l1_vmx_code() {
	prepare_for_vmx_operation(vmx);

	load_vmcs(vmx);

	prepare_vmcs(vmx, NULL);
	vmwrite(GUEST_IDTR_LIMIT, 0);
	...
	vmwrite(EXCEPTION_BITMAP, INTERCEPT_SS_GP_DF);
	...
}

Could the INT3 and INTn vectoring checks in l2_guest_code() and
l1_assert_vectoring_exit() be added to
tools/testing/selftests/kvm/x86/nested_exceptions_test.c instead of adding a
separate x86/vmx_soft_int_vectoring_test target to TEST_GEN_PROGS_x86 in
tools/testing/selftests/kvm/Makefile.kvm?

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Sashiko AI review · https://sashiko.dev/#/patchset/20261021042603.608292-1-ma.mandourr@gmail.com?part=2