Re: [PATCH] x86/hyper-v: Don't WARN on VM-Enter if eVMCS sees VMFUNC[63:32] != 0

[Manuel Andreas]

If relevant I utilized the following KVM unit test to trigger the WARN_ON_ONCE:

---
 x86/unittests.cfg |  6 ++++++
 x86/vmx.h         |  1 +
 x86/vmx_tests.c   | 17 +++++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/x86/unittests.cfg b/x86/unittests.cfg
index ae731a93..e46ecad1 100644
--- a/x86/unittests.cfg
+++ b/x86/unittests.cfg
@@ -482,6 +482,12 @@ arch = x86_64
 groups = vmx nested_exception
 check = /sys/module/kvm_intel/parameters/allow_smaller_maxphyaddr=Y

+[vmx_hyperv_vm_func_ctrls_warn]
+file = vmx.flat
+extra_params = -cpu max,+vmx,hv-vapic,hv-evmcs -append vmx_hyperv_vm_func_ctrls_warn
+arch = x86_64
+groups = vmx
+
 [debug]
 file = debug.flat
 arch = x86_64
diff --git a/x86/vmx.h b/x86/vmx.h
index f27ecd72..8d26b1a5 100644
--- a/x86/vmx.h
+++ b/x86/vmx.h
@@ -207,6 +207,7 @@ enum Encoding {
 	APIC_VIRT_ADDR		= 0x2012ul,
 	APIC_ACCS_ADDR		= 0x2014ul,
 	POSTED_INTR_DESC_ADDR	= 0x2016ul,
+	VM_FUNCTION_CONTROL     = 0x2018ul,
 	EPTP			= 0x201aul,
 	EPTP_HI			= 0x201bul,
 	VMREAD_BITMAP           = 0x2026ul,
diff --git a/x86/vmx_tests.c b/x86/vmx_tests.c
index 2c0feca0..287336be 100644
--- a/x86/vmx_tests.c
+++ b/x86/vmx_tests.c
@@ -12084,6 +12084,22 @@ static void vmx_cet_test(void)
 	test_set_guest_finished();
 }

+static void vmx_hyperv_vm_func_ctrls_warn_guest(void) {
+	vmcall();
+}
+
+static void vmx_hyperv_vm_func_ctrls_warn(void)
+{
+	/* Set the unsupported bit */
+	vmcs_write(VM_FUNCTION_CONTROL, 1UL << 32UL);
+
+	test_set_guest(vmx_hyperv_vm_func_ctrls_warn_guest);
+	enter_guest();
+
+	test_set_guest_finished();
+	report(true, "hyperv warn on should have triggered!");
+}
+
 #define TEST(name) { #name, .v2 = name }

 /* name/init/guest_main/exit_handler/vmfail_handler */
@@ -12202,5 +12218,6 @@ struct vmx_test vmx_tests[] = {
 	TEST(vmx_canonical_test),
 	/* "Load CET" VM-entry/exit controls tests. */
 	TEST(vmx_cet_test),
+	TEST(vmx_hyperv_vm_func_ctrls_warn),
 	{ NULL, NULL, NULL, NULL },
 };
--
2.47.3