KVM: arm64: Slightly improve debug save/restore functions

The debug save/restore functions can be improved by using the has_vhe() static key instead of the instruction alternative. Using the static key uses the same paradigm as we're going to use elsewhere, it makes the code more readable, and it generates slightly better code (no stack setups and function calls unless necessary). We also use a static key on the restore path, because it will be marginally faster than loading a value from memory. Finally, we don't have to conditionally clear the debug dirty flag if it's set, we can just clear it. Reviewed-by: Marc Zyngier <[email protected]> Reviewed-by: Andrew Jones <[email protected]> Signed-off-by: Christoffer Dall <[email protected]> Signed-off-by: Marc Zyngier <[email protected]>
josf · Mar 19, 2018 · 5742d04 · 5742d04
1 parent 54ceb1b
commit 5742d04
Showing 1 changed file with 12 additions and 14 deletions.
diff --git a/arch/arm64/kvm/hyp/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c
@@ -66,11 +66,6 @@
 	default:	write_debug(ptr[0], reg, 0);			\
 	}
 
-static void __hyp_text __debug_save_spe_vhe(u64 *pmscr_el1)
-{
-	/* The vcpu can run. but it can't hide. */
-}
-
 static void __hyp_text __debug_save_spe_nvhe(u64 *pmscr_el1)
 {
 	u64 reg;
@@ -103,11 +98,7 @@ static void __hyp_text __debug_save_spe_nvhe(u64 *pmscr_el1)
 	dsb(nsh);
 }
 
-static hyp_alternate_select(__debug_save_spe,
-			    __debug_save_spe_nvhe, __debug_save_spe_vhe,
-			    ARM64_HAS_VIRT_HOST_EXTN);
-
-static void __hyp_text __debug_restore_spe(u64 pmscr_el1)
+static void __hyp_text __debug_restore_spe_nvhe(u64 pmscr_el1)
 {
 	if (!pmscr_el1)
 		return;
@@ -168,17 +159,24 @@ void __hyp_text __debug_cond_save_host_state(struct kvm_vcpu *vcpu)
 {
 	__debug_save_state(vcpu, &vcpu->arch.host_debug_state.regs,
 			   kern_hyp_va(vcpu->arch.host_cpu_context));
-	__debug_save_spe()(&vcpu->arch.host_debug_state.pmscr_el1);
+
+	/*
+	 * Non-VHE: Disable and flush SPE data generation
+	 * VHE: The vcpu can run, but it can't hide.
+	 */
+	if (!has_vhe())
+		__debug_save_spe_nvhe(&vcpu->arch.host_debug_state.pmscr_el1);
 }
 
 void __hyp_text __debug_cond_restore_host_state(struct kvm_vcpu *vcpu)
 {
-	__debug_restore_spe(vcpu->arch.host_debug_state.pmscr_el1);
+	if (!has_vhe())
+		__debug_restore_spe_nvhe(vcpu->arch.host_debug_state.pmscr_el1);
+
 	__debug_restore_state(vcpu, &vcpu->arch.host_debug_state.regs,
 			      kern_hyp_va(vcpu->arch.host_cpu_context));
 
-	if (vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY)
-		vcpu->arch.debug_flags &= ~KVM_ARM64_DEBUG_DIRTY;
+	vcpu->arch.debug_flags &= ~KVM_ARM64_DEBUG_DIRTY;
 }
 
 u32 __hyp_text __kvm_get_mdcr_el2(void)