[PATCH v7 1/2] KVM: VMX: Bury all of the VMX preemption timer code under CONFIG_X86_64=y

Double down on using the VMX preemption timer only for 64-bit kernels, and
bury the setup and runtime adjustment code, and all global variables, under
CONFIG_X86_64=y.  This will allow addressing a widespread Intel erratum
without running afoul of unused-but-set-variable and __udivdi3() errors on
32-bit kernels.

No functional change intended.

Reviewed-by: Binbin Wu <[email protected]>
Reviewed-by: Chao Gao <[email protected]>
Signed-off-by: Sean Christopherson <[email protected]>
---
 arch/x86/kvm/vmx/vmx.c | 122 +++++++++++++++++++++++------------------
 1 file changed, 69 insertions(+), 53 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index e4b9ac7fed9f..a07faa066ef0 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -150,10 +150,12 @@ module_param(dump_invalid_vmcs, bool, 0644);
 #define KVM_VMX_TSC_MULTIPLIER_MAX     0xffffffffffffffffULL
 
 /* Guest_tsc -> host_tsc conversion requires 64-bit division.  */
+#ifdef CONFIG_X86_64
 static int __read_mostly cpu_preemption_timer_multi;
 static bool __read_mostly enable_preemption_timer = 1;
-#ifdef CONFIG_X86_64
 module_param_named(preemption_timer, enable_preemption_timer, bool, S_IRUGO);
+#else
+#define enable_preemption_timer false
 #endif
 
 extern bool __read_mostly allow_smaller_maxphyaddr;
@@ -7408,32 +7410,6 @@ static void vmx_refresh_guest_perf_global_control(struct kvm_vcpu *vcpu)
 	pmu->global_ctrl = vmcs_read64(GUEST_IA32_PERF_GLOBAL_CTRL);
 }
 
-static void vmx_update_hv_timer(struct kvm_vcpu *vcpu, bool force_immediate_exit)
-{
-	struct vcpu_vmx *vmx = to_vmx(vcpu);
-	u64 tscl;
-	u32 delta_tsc;
-
-	if (force_immediate_exit) {
-		vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, 0);
-		vmx->loaded_vmcs->hv_timer_soft_disabled = false;
-	} else if (vmx->hv_deadline_tsc != -1) {
-		tscl = rdtsc();
-		if (vmx->hv_deadline_tsc > tscl)
-			/* set_hv_timer ensures the delta fits in 32-bits */
-			delta_tsc = (u32)((vmx->hv_deadline_tsc - tscl) >>
-				cpu_preemption_timer_multi);
-		else
-			delta_tsc = 0;
-
-		vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, delta_tsc);
-		vmx->loaded_vmcs->hv_timer_soft_disabled = false;
-	} else if (!vmx->loaded_vmcs->hv_timer_soft_disabled) {
-		vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, -1);
-		vmx->loaded_vmcs->hv_timer_soft_disabled = true;
-	}
-}
-
 void noinstr vmx_update_host_rsp(struct vcpu_vmx *vmx, unsigned long host_rsp)
 {
 	if (unlikely(host_rsp != vmx->loaded_vmcs->host_state.rsp)) {
@@ -7519,6 +7495,8 @@ static noinstr void vmx_vcpu_enter_exit(struct kvm_vcpu *vcpu,
 	guest_state_exit_irqoff();
 }
 
+static void vmx_update_hv_timer(struct kvm_vcpu *vcpu, bool force_immediate_exit);
+
 fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags)
 {
 	bool force_immediate_exit = run_flags & KVM_RUN_FORCE_IMMEDIATE_EXIT;
@@ -8328,6 +8306,36 @@ static inline int u64_shl_div_u64(u64 a, unsigned int shift,
 	return 0;
 }
 
+static __init void vmx_setup_preemption_timer(void)
+{
+	if (!cpu_has_vmx_preemption_timer())
+		enable_preemption_timer = false;
+
+	if (enable_preemption_timer) {
+		u64 use_timer_freq = 5000ULL * 1000 * 1000;
+
+		cpu_preemption_timer_multi =
+			vmx_misc_preemption_timer_rate(vmcs_config.misc);
+
+		if (tsc_khz)
+			use_timer_freq = (u64)tsc_khz * 1000;
+		use_timer_freq >>= cpu_preemption_timer_multi;
+
+		/*
+		 * KVM "disables" the preemption timer by setting it to its max
+		 * value.  Don't use the timer if it might cause spurious exits
+		 * at a rate faster than 0.1 Hz (of uninterrupted guest time).
+		 */
+		if (use_timer_freq > 0xffffffffu / 10)
+			enable_preemption_timer = false;
+	}
+
+	if (!enable_preemption_timer) {
+		vt_x86_ops.set_hv_timer = NULL;
+		vt_x86_ops.cancel_hv_timer = NULL;
+	}
+}
+
 int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc,
 		     bool *expired)
 {
@@ -8372,6 +8380,39 @@ void vmx_cancel_hv_timer(struct kvm_vcpu *vcpu)
 {
 	to_vmx(vcpu)->hv_deadline_tsc = -1;
 }
+
+static void vmx_update_hv_timer(struct kvm_vcpu *vcpu, bool force_immediate_exit)
+{
+	struct vcpu_vmx *vmx = to_vmx(vcpu);
+	u64 tscl;
+	u32 delta_tsc;
+
+	if (force_immediate_exit) {
+		vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, 0);
+		vmx->loaded_vmcs->hv_timer_soft_disabled = false;
+	} else if (vmx->hv_deadline_tsc != -1) {
+		tscl = rdtsc();
+		if (vmx->hv_deadline_tsc > tscl)
+			/* set_hv_timer ensures the delta fits in 32-bits */
+			delta_tsc = (u32)((vmx->hv_deadline_tsc - tscl) >>
+				cpu_preemption_timer_multi);
+		else
+			delta_tsc = 0;
+
+		vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, delta_tsc);
+		vmx->loaded_vmcs->hv_timer_soft_disabled = false;
+	} else if (!vmx->loaded_vmcs->hv_timer_soft_disabled) {
+		vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, -1);
+		vmx->loaded_vmcs->hv_timer_soft_disabled = true;
+	}
+}
+#else
+static __init void vmx_setup_preemption_timer(void) { }
+
+static void vmx_update_hv_timer(struct kvm_vcpu *vcpu, bool force_immediate_exit)
+{
+	BUILD_BUG_ON(1);
+}
 #endif
 
 void vmx_update_cpu_dirty_logging(struct kvm_vcpu *vcpu)
@@ -8734,32 +8775,7 @@ __init int vmx_hardware_setup(void)
 	if (!enable_ept || !enable_ept_ad_bits || !cpu_has_vmx_pml())
 		enable_pml = 0;
 
-	if (!cpu_has_vmx_preemption_timer())
-		enable_preemption_timer = false;
-
-	if (enable_preemption_timer) {
-		u64 use_timer_freq = 5000ULL * 1000 * 1000;
-
-		cpu_preemption_timer_multi =
-			vmx_misc_preemption_timer_rate(vmcs_config.misc);
-
-		if (tsc_khz)
-			use_timer_freq = (u64)tsc_khz * 1000;
-		use_timer_freq >>= cpu_preemption_timer_multi;
-
-		/*
-		 * KVM "disables" the preemption timer by setting it to its max
-		 * value.  Don't use the timer if it might cause spurious exits
-		 * at a rate faster than 0.1 Hz (of uninterrupted guest time).
-		 */
-		if (use_timer_freq > 0xffffffffu / 10)
-			enable_preemption_timer = false;
-	}
-
-	if (!enable_preemption_timer) {
-		vt_x86_ops.set_hv_timer = NULL;
-		vt_x86_ops.cancel_hv_timer = NULL;
-	}
+	vmx_setup_preemption_timer();
 
 	kvm_caps.supported_mce_cap |= MCG_LMCE_P;
 	kvm_caps.supported_mce_cap |= MCG_CMCI_P;
-- 
2.55.0.508.g3f0d502094-goog