[1/7] KVM: x86: Add module parameter for supporting VMware backdoor

Commit Message

Liran Alon Dec. 18, 2017, 9:45 a.m. UTC

Support access to VMware backdoor requires KVM to intercept #GP
exceptions from guest which introduce slight performance hit.
Therefore, control this support by module parameter.

Note that module parameter is exported as it should be consumed by
kvm_intel & kvm_amd to determine if they should intercept #GP or not.

This commit doesn't change semantics.
It is done as a preparation for future commits.

Signed-off-by: Liran Alon <[e-mail]>
Reviewed-by: Nikita Leshenko <[e-mail]>
Signed-off-by: Krish Sadhukhan <[e-mail]>
---
 Documentation/admin-guide/kernel-parameters.txt | 3 +++
 arch/x86/kvm/x86.c                              | 4 ++++
 arch/x86/kvm/x86.h                              | 2 ++
 3 files changed, 9 insertions(+)

Patch

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6571fbfdb2a1..05737a507ddc 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1867,6 +1867,9 @@ 
 	kvm.ignore_msrs=[KVM] Ignore guest accesses to unhandled MSRs.
 			Default is 0 (don't ignore, but inject #GP)
 
+	kvm.enable_vmware_backdoor=[KVM] Support VMware backdoor PV interface.
+				   Default is false (don't support).
+
 	kvm.mmu_audit=	[KVM] This is a R/W parameter which allows audit
 			KVM MMU at runtime.
 			Default is 0 (off)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index faf843c9b916..5fef09674de1 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -138,6 +138,10 @@ 
 static bool __read_mostly vector_hashing = true;
 module_param(vector_hashing, bool, S_IRUGO);
 
+bool __read_mostly enable_vmware_backdoor = false;
+module_param(enable_vmware_backdoor, bool, S_IRUGO);
+EXPORT_SYMBOL_GPL(enable_vmware_backdoor);
+
 #define KVM_NR_SHARED_MSRS 16
 
 struct kvm_shared_msrs_global {
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index d0b95b7a90b4..1909603cb816 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -241,6 +241,8 @@  bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
 
 extern unsigned int lapic_timer_advance_ns;
 
+extern bool enable_vmware_backdoor;
+
 extern struct static_key kvm_no_apic_vcpu;
 
 static inline u64 nsec_to_cycles(struct kvm_vcpu *vcpu, u64 nsec)