[RFC PATCH 03/18] KVM: x86: Add module parameter for Intel MBEC

[Jon Kohler <jon@nutanix.com>]

Add 'enable_pt_guest_exec_control' module parameter to x86 code, with
default value false. This parameter will control enablement for
exposing Intel Mode Based Execution Control (aka MBEC).

Place parameter in x86 common code as, notionally, AMD has a similar
feature called Guest Mode Execute Trap (GMET), which may want to build
off of this parameter in the future, similar to how 'enable_apicv' is
shared across both Intel APICv and AMD AVIC.

Signed-off-by: Jon Kohler <jon@nutanix.com>

---
 arch/x86/include/asm/kvm_host.h | 1 +
 arch/x86/kvm/x86.c              | 4 ++++
 2 files changed, 5 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7cf2025a64a0..fd37dad38670 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1883,6 +1883,7 @@ struct kvm_arch_async_pf {
 extern u32 __read_mostly kvm_nr_uret_msrs;
 extern bool __read_mostly allow_smaller_maxphyaddr;
 extern bool __read_mostly enable_apicv;
+extern bool __read_mostly enable_pt_guest_exec_control;
 extern struct kvm_x86_ops kvm_x86_ops;
 
 #define kvm_x86_call(func) static_call(kvm_x86_##func)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7bae9e9cc14e..4b2fbb9088ea 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -197,6 +197,10 @@ module_param(eager_page_split, bool, 0644);
 static bool __read_mostly mitigate_smt_rsb;
 module_param(mitigate_smt_rsb, bool, 0444);
 
+bool __read_mostly enable_pt_guest_exec_control;
+EXPORT_SYMBOL_GPL(enable_pt_guest_exec_control);
+module_param(enable_pt_guest_exec_control, bool, 0444);
+
 /*
  * Restoring the host value for MSRs that are only consumed when running in
  * usermode, e.g. SYSCALL MSRs and TSC_AUX, can be deferred until the CPU
-- 
2.43.0