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KVM: VMX: Bury all of the VMX preemption timer code under CONFIG_X86_64=y

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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 <binbin.wu@linux.intel.com>
Reviewed-by: Chao Gao <chao.gao@intel.com>
Link: https://patch.msgid.link/20260731171926.2629627-2-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2026-07-31 10:19:25 -07:00
parent 05a0b701d1
commit d0dea3ed84
1 changed files with 69 additions and 53 deletions
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122
arch/x86/kvm/vmx/vmx.c
View File

@ -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;