[RFC PATCH v6 08/36] KVM: nVMX: Use CC() macro to handle eVMCS unsupported controls checks

Sean Christopherson
2022-08-24T03:03:50Z

Locally #define and use the nested virtualization Consistency Check (CC)
macro to handle eVMCS unsupported controls checks. Using the macro loses
the existing printing of the unsupported controls, but that's a feature
and not a bug. The existing approach is flawed because the @err param to
trace_kvm_nested_vmenter_failed() is the error code, not the error value.

The eVMCS trickery mostly works as __print_symbolic() falls back to
printing the raw hex value, but that subtly relies on not having a match
between the unsupported value and VMX_VMENTER_INSTRUCTION_ERRORS.

If it's really truly necessary to snapshot the bad value, then the
tracepoint can be extended in the future.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/vmx/evmcs.c | 68 ++++++++++++++--------------------------
1 file changed, 24 insertions(+), 44 deletions(-)

diff --git a/arch/x86/kvm/vmx/evmcs.c b/arch/x86/kvm/vmx/evmcs.c
index 10fc0be49f96..3bf8681e5239 100644
--- a/arch/x86/kvm/vmx/evmcs.c
+++ b/arch/x86/kvm/vmx/evmcs.c
@@ -10,6 +10,8 @@
#include "vmx.h"
#include "trace.h"

+#define CC KVM_NESTED_VMENTER_CONSISTENCY_CHECK
+
DEFINE_STATIC_KEY_FALSE(enable_evmcs);

#define EVMCS1_OFFSET(x) offsetof(struct hv_enlightened_vmcs, x)
@@ -417,57 +419,35 @@ void nested_evmcs_filter_control_msr(u32 msr_index, u64 *pdata)
*pdata = ctl_low | ((u64)ctl_high << 32);
}

+static bool nested_evmcs_is_valid_controls(enum evmcs_ctrl_type ctrl_type,
+ u32 val)
+{
+ return !(val & evmcs_get_unsupported_ctls(ctrl_type));
+}
+
int nested_evmcs_check_controls(struct vmcs12 *vmcs12)
{
- int ret = 0;
- u32 unsupp_ctl;
+ if (CC(!nested_evmcs_is_valid_controls(EVMCS_PINCTRL,
+ vmcs12->pin_based_vm_exec_control)))
+ return -EINVAL;

- unsupp_ctl = vmcs12->pin_based_vm_exec_control &
- evmcs_get_unsupported_ctls(EVMCS_PINCTRL);
- if (unsupp_ctl) {
- trace_kvm_nested_vmenter_failed(
- "eVMCS: unsupported pin-based VM-execution controls",
- unsupp_ctl);
- ret = -EINVAL;
- }
+ if (CC(!nested_evmcs_is_valid_controls(EVMCS_2NDEXEC,
+ vmcs12->secondary_vm_exec_control)))
+ return -EINVAL;

- unsupp_ctl = vmcs12->secondary_vm_exec_control &
- evmcs_get_unsupported_ctls(EVMCS_2NDEXEC);
- if (unsupp_ctl) {
- trace_kvm_nested_vmenter_failed(
- "eVMCS: unsupported secondary VM-execution controls",
- unsupp_ctl);
- ret = -EINVAL;
- }
+ if (CC(!nested_evmcs_is_valid_controls(EVMCS_EXIT_CTRLS,
+ vmcs12->vm_exit_controls)))
+ return -EINVAL;

- unsupp_ctl = vmcs12->vm_exit_controls &
- evmcs_get_unsupported_ctls(EVMCS_EXIT_CTRLS);
- if (unsupp_ctl) {
- trace_kvm_nested_vmenter_failed(
- "eVMCS: unsupported VM-exit controls",
- unsupp_ctl);
- ret = -EINVAL;
- }
+ if (CC(!nested_evmcs_is_valid_controls(EVMCS_ENTRY_CTRLS,
+ vmcs12->vm_entry_controls)))
+ return -EINVAL;

- unsupp_ctl = vmcs12->vm_entry_controls &
- evmcs_get_unsupported_ctls(EVMCS_ENTRY_CTRLS);
- if (unsupp_ctl) {
- trace_kvm_nested_vmenter_failed(
- "eVMCS: unsupported VM-entry controls",
- unsupp_ctl);
- ret = -EINVAL;
- }
+ if (CC(!nested_evmcs_is_valid_controls(EVMCS_VMFUNC,
+ vmcs12->vm_function_control)))
+ return -EINVAL;

- unsupp_ctl = vmcs12->vm_function_control &
- evmcs_get_unsupported_ctls(EVMCS_VMFUNC);
- if (unsupp_ctl) {
- trace_kvm_nested_vmenter_failed(
- "eVMCS: unsupported VM-function controls",
- unsupp_ctl);
- ret = -EINVAL;
- }
-
- return ret;
+ return 0;
}

int nested_enable_evmcs(struct kvm_vcpu *vcpu,
--
2.37.1.595.g718a3a8f04-goog