kvm: vmx: hook preemption timer support
Hook the VMX preemption timer to the "hv timer" functionality added
by the previous patch. This includes: checking if the feature is
supported, if the feature is broken on the CPU, the hooks to
setup/clean the VMX preemption timer, arming the timer on vmentry
and handling the vmexit.
A module parameter states if the VMX preemption timer should be
utilized.
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
[Move hv_deadline_tsc to struct vcpu_vmx, use -1 as the "unset" value.
Put all VMX bits here. Enable it by default #yolo. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 29e78fd..e185649 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -110,6 +110,13 @@
#define KVM_VMX_TSC_MULTIPLIER_MAX 0xffffffffffffffffULL
+/* Guest_tsc -> host_tsc conversion requires 64-bit division. */
+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);
+#endif
+
#define KVM_GUEST_CR0_MASK (X86_CR0_NW | X86_CR0_CD)
#define KVM_VM_CR0_ALWAYS_ON_UNRESTRICTED_GUEST (X86_CR0_WP | X86_CR0_NE)
#define KVM_VM_CR0_ALWAYS_ON \
@@ -597,6 +604,9 @@
#define PML_ENTITY_NUM 512
struct page *pml_pg;
+ /* apic deadline value in host tsc */
+ u64 hv_deadline_tsc;
+
u64 current_tsc_ratio;
bool guest_pkru_valid;
@@ -1056,6 +1066,61 @@
SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY;
}
+/*
+ * Comment's format: document - errata name - stepping - processor name.
+ * Refer from
+ * https://www.virtualbox.org/svn/vbox/trunk/src/VBox/VMM/VMMR0/HMR0.cpp
+ */
+static u32 vmx_preemption_cpu_tfms[] = {
+/* 323344.pdf - BA86 - D0 - Xeon 7500 Series */
+0x000206E6,
+/* 323056.pdf - AAX65 - C2 - Xeon L3406 */
+/* 322814.pdf - AAT59 - C2 - i7-600, i5-500, i5-400 and i3-300 Mobile */
+/* 322911.pdf - AAU65 - C2 - i5-600, i3-500 Desktop and Pentium G6950 */
+0x00020652,
+/* 322911.pdf - AAU65 - K0 - i5-600, i3-500 Desktop and Pentium G6950 */
+0x00020655,
+/* 322373.pdf - AAO95 - B1 - Xeon 3400 Series */
+/* 322166.pdf - AAN92 - B1 - i7-800 and i5-700 Desktop */
+/*
+ * 320767.pdf - AAP86 - B1 -
+ * i7-900 Mobile Extreme, i7-800 and i7-700 Mobile
+ */
+0x000106E5,
+/* 321333.pdf - AAM126 - C0 - Xeon 3500 */
+0x000106A0,
+/* 321333.pdf - AAM126 - C1 - Xeon 3500 */
+0x000106A1,
+/* 320836.pdf - AAJ124 - C0 - i7-900 Desktop Extreme and i7-900 Desktop */
+0x000106A4,
+ /* 321333.pdf - AAM126 - D0 - Xeon 3500 */
+ /* 321324.pdf - AAK139 - D0 - Xeon 5500 */
+ /* 320836.pdf - AAJ124 - D0 - i7-900 Extreme and i7-900 Desktop */
+0x000106A5,
+};
+
+static inline bool cpu_has_broken_vmx_preemption_timer(void)
+{
+ u32 eax = cpuid_eax(0x00000001), i;
+
+ /* Clear the reserved bits */
+ eax &= ~(0x3U << 14 | 0xfU << 28);
+ for (i = 0; i < sizeof(vmx_preemption_cpu_tfms)/sizeof(u32); i++)
+ if (eax == vmx_preemption_cpu_tfms[i])
+ return true;
+
+ return false;
+}
+
+static inline bool cpu_has_vmx_preemption_timer(void)
+{
+ if (cpu_has_broken_vmx_preemption_timer())
+ return false;
+
+ return vmcs_config.pin_based_exec_ctrl &
+ PIN_BASED_VMX_PREEMPTION_TIMER;
+}
+
static inline bool cpu_has_vmx_posted_intr(void)
{
return IS_ENABLED(CONFIG_X86_LOCAL_APIC) &&
@@ -3308,7 +3373,8 @@
return -EIO;
min = PIN_BASED_EXT_INTR_MASK | PIN_BASED_NMI_EXITING;
- opt = PIN_BASED_VIRTUAL_NMIS | PIN_BASED_POSTED_INTR;
+ opt = PIN_BASED_VIRTUAL_NMIS | PIN_BASED_POSTED_INTR |
+ PIN_BASED_VMX_PREEMPTION_TIMER;
if (adjust_vmx_controls(min, opt, MSR_IA32_VMX_PINBASED_CTLS,
&_pin_based_exec_control) < 0)
return -EIO;
@@ -4781,6 +4847,8 @@
if (!kvm_vcpu_apicv_active(&vmx->vcpu))
pin_based_exec_ctrl &= ~PIN_BASED_POSTED_INTR;
+ /* Enable the preemption timer dynamically */
+ pin_based_exec_ctrl &= ~PIN_BASED_VMX_PREEMPTION_TIMER;
return pin_based_exec_ctrl;
}
@@ -4899,6 +4967,7 @@
/* Control */
vmcs_write32(PIN_BASED_VM_EXEC_CONTROL, vmx_pin_based_exec_ctrl(vmx));
+ vmx->hv_deadline_tsc = -1;
vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, vmx_exec_control(vmx));
@@ -6389,6 +6458,17 @@
kvm_x86_ops->enable_log_dirty_pt_masked = NULL;
}
+ if (cpu_has_vmx_preemption_timer() && enable_preemption_timer) {
+ u64 vmx_msr;
+
+ rdmsrl(MSR_IA32_VMX_MISC, vmx_msr);
+ cpu_preemption_timer_multi =
+ vmx_msr & VMX_MISC_PREEMPTION_TIMER_RATE_MASK;
+ } else {
+ kvm_x86_ops->set_hv_timer = NULL;
+ kvm_x86_ops->cancel_hv_timer = NULL;
+ }
+
kvm_set_posted_intr_wakeup_handler(wakeup_handler);
return alloc_kvm_area();
@@ -7564,6 +7644,12 @@
return 1;
}
+static int handle_preemption_timer(struct kvm_vcpu *vcpu)
+{
+ kvm_lapic_expired_hv_timer(vcpu);
+ return 1;
+}
+
/*
* The exit handlers return 1 if the exit was handled fully and guest execution
* may resume. Otherwise they set the kvm_run parameter to indicate what needs
@@ -7615,6 +7701,7 @@
[EXIT_REASON_XRSTORS] = handle_xrstors,
[EXIT_REASON_PML_FULL] = handle_pml_full,
[EXIT_REASON_PCOMMIT] = handle_pcommit,
+ [EXIT_REASON_PREEMPTION_TIMER] = handle_preemption_timer,
};
static const int kvm_vmx_max_exit_handlers =
@@ -8623,6 +8710,26 @@
msrs[i].host);
}
+void vmx_arm_hv_timer(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+ u64 tscl;
+ u32 delta_tsc;
+
+ if (vmx->hv_deadline_tsc == -1)
+ return;
+
+ tscl = rdtsc();
+ if (vmx->hv_deadline_tsc > tscl)
+ /* sure to be 32 bit only because checked on set_hv_timer */
+ delta_tsc = (u32)((vmx->hv_deadline_tsc - tscl) >>
+ cpu_preemption_timer_multi);
+ else
+ delta_tsc = 0;
+
+ vmcs_write32(VMX_PREEMPTION_TIMER_VALUE, delta_tsc);
+}
+
static void __noclone vmx_vcpu_run(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -8672,6 +8779,8 @@
atomic_switch_perf_msrs(vmx);
debugctlmsr = get_debugctlmsr();
+ vmx_arm_hv_timer(vcpu);
+
vmx->__launched = vmx->loaded_vmcs->launched;
asm(
/* Store host registers */
@@ -10662,6 +10771,64 @@
return X86EMUL_CONTINUE;
}
+#ifdef CONFIG_X86_64
+/* (a << shift) / divisor, return 1 if overflow otherwise 0 */
+static inline int u64_shl_div_u64(u64 a, unsigned int shift,
+ u64 divisor, u64 *result)
+{
+ u64 low = a << shift, high = a >> (64 - shift);
+
+ /* To avoid the overflow on divq */
+ if (high >= divisor)
+ return 1;
+
+ /* Low hold the result, high hold rem which is discarded */
+ asm("divq %2\n\t" : "=a" (low), "=d" (high) :
+ "rm" (divisor), "0" (low), "1" (high));
+ *result = low;
+
+ return 0;
+}
+
+static int vmx_set_hv_timer(struct kvm_vcpu *vcpu, u64 guest_deadline_tsc)
+{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+ u64 tscl = rdtsc(), delta_tsc;
+
+ delta_tsc = guest_deadline_tsc - kvm_read_l1_tsc(vcpu, tscl);
+
+ /* Convert to host delta tsc if tsc scaling is enabled */
+ if (vcpu->arch.tsc_scaling_ratio != kvm_default_tsc_scaling_ratio &&
+ u64_shl_div_u64(delta_tsc,
+ kvm_tsc_scaling_ratio_frac_bits,
+ vcpu->arch.tsc_scaling_ratio,
+ &delta_tsc))
+ return -ERANGE;
+
+ /*
+ * If the delta tsc can't fit in the 32 bit after the multi shift,
+ * we can't use the preemption timer.
+ * It's possible that it fits on later vmentries, but checking
+ * on every vmentry is costly so we just use an hrtimer.
+ */
+ if (delta_tsc >> (cpu_preemption_timer_multi + 32))
+ return -ERANGE;
+
+ vmx->hv_deadline_tsc = tscl + delta_tsc;
+ vmcs_set_bits(PIN_BASED_VM_EXEC_CONTROL,
+ PIN_BASED_VMX_PREEMPTION_TIMER);
+ return 0;
+}
+
+static void vmx_cancel_hv_timer(struct kvm_vcpu *vcpu)
+{
+ struct vcpu_vmx *vmx = to_vmx(vcpu);
+ vmx->hv_deadline_tsc = -1;
+ vmcs_clear_bits(PIN_BASED_VM_EXEC_CONTROL,
+ PIN_BASED_VMX_PREEMPTION_TIMER);
+}
+#endif
+
static void vmx_sched_in(struct kvm_vcpu *vcpu, int cpu)
{
if (ple_gap)
@@ -10777,6 +10944,9 @@
if (pi_pre_block(vcpu))
return 1;
+ if (kvm_lapic_hv_timer_in_use(vcpu))
+ kvm_lapic_switch_to_sw_timer(vcpu);
+
return 0;
}
@@ -10823,6 +10993,9 @@
static void vmx_post_block(struct kvm_vcpu *vcpu)
{
+ if (kvm_x86_ops->set_hv_timer)
+ kvm_lapic_switch_to_hv_timer(vcpu);
+
pi_post_block(vcpu);
}
@@ -11038,6 +11211,11 @@
.pmu_ops = &intel_pmu_ops,
.update_pi_irte = vmx_update_pi_irte,
+
+#ifdef CONFIG_X86_64
+ .set_hv_timer = vmx_set_hv_timer,
+ .cancel_hv_timer = vmx_cancel_hv_timer,
+#endif
};
static int __init vmx_init(void)