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Date: Thu, 8 Apr 2021 20:20:47 +0000
From: Sean Christopherson <seanjc@...gle.com>
To: Wanpeng Li <kernellwp@...il.com>
Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
Paolo Bonzini <pbonzini@...hat.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH] x86/kvm: Don't alloc __pv_cpu_mask when !CONFIG_SMP
On Wed, Apr 07, 2021, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@...cent.com>
>
> Enable PV TLB shootdown when !CONFIG_SMP doesn't make sense. Let's move
> it inside CONFIG_SMP. In addition, we can avoid alloc __pv_cpu_mask when
> !CONFIG_SMP and get rid of 'alloc' variable in kvm_alloc_cpumask.
...
> +static bool pv_tlb_flush_supported(void) { return false; }
> +static bool pv_ipi_supported(void) { return false; }
> +static void kvm_flush_tlb_others(const struct cpumask *cpumask,
> + const struct flush_tlb_info *info) { }
> +static void kvm_setup_pv_ipi(void) { }
If you shuffle things around a bit more, you can avoid these stubs, and hide the
definition of __pv_cpu_mask behind CONFIG_SMP, too.
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 5e78e01ca3b4..13c6b1c7c01b 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -451,6 +451,8 @@ static void __init sev_map_percpu_data(void)
}
}
+#ifdef CONFIG_SMP
+
static bool pv_tlb_flush_supported(void)
{
return (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
@@ -460,8 +462,6 @@ static bool pv_tlb_flush_supported(void)
static DEFINE_PER_CPU(cpumask_var_t, __pv_cpu_mask);
-#ifdef CONFIG_SMP
-
static bool pv_ipi_supported(void)
{
return kvm_para_has_feature(KVM_FEATURE_PV_SEND_IPI);
@@ -574,45 +574,6 @@ static void kvm_smp_send_call_func_ipi(const struct cpumask *mask)
}
}
-static void __init kvm_smp_prepare_boot_cpu(void)
-{
- /*
- * Map the per-cpu variables as decrypted before kvm_guest_cpu_init()
- * shares the guest physical address with the hypervisor.
- */
- sev_map_percpu_data();
-
- kvm_guest_cpu_init();
- native_smp_prepare_boot_cpu();
- kvm_spinlock_init();
-}
-
-static void kvm_guest_cpu_offline(void)
-{
- kvm_disable_steal_time();
- if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
- wrmsrl(MSR_KVM_PV_EOI_EN, 0);
- kvm_pv_disable_apf();
- apf_task_wake_all();
-}
-
-static int kvm_cpu_online(unsigned int cpu)
-{
- local_irq_disable();
- kvm_guest_cpu_init();
- local_irq_enable();
- return 0;
-}
-
-static int kvm_cpu_down_prepare(unsigned int cpu)
-{
- local_irq_disable();
- kvm_guest_cpu_offline();
- local_irq_enable();
- return 0;
-}
-#endif
-
static void kvm_flush_tlb_others(const struct cpumask *cpumask,
const struct flush_tlb_info *info)
{
@@ -639,6 +600,63 @@ static void kvm_flush_tlb_others(const struct cpumask *cpumask,
native_flush_tlb_others(flushmask, info);
}
+static void __init kvm_smp_prepare_boot_cpu(void)
+{
+ /*
+ * Map the per-cpu variables as decrypted before kvm_guest_cpu_init()
+ * shares the guest physical address with the hypervisor.
+ */
+ sev_map_percpu_data();
+
+ kvm_guest_cpu_init();
+ native_smp_prepare_boot_cpu();
+ kvm_spinlock_init();
+}
+
+static void kvm_guest_cpu_offline(void)
+{
+ kvm_disable_steal_time();
+ if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
+ wrmsrl(MSR_KVM_PV_EOI_EN, 0);
+ kvm_pv_disable_apf();
+ apf_task_wake_all();
+}
+
+static int kvm_cpu_online(unsigned int cpu)
+{
+ local_irq_disable();
+ kvm_guest_cpu_init();
+ local_irq_enable();
+ return 0;
+}
+
+static int kvm_cpu_down_prepare(unsigned int cpu)
+{
+ local_irq_disable();
+ kvm_guest_cpu_offline();
+ local_irq_enable();
+ return 0;
+}
+
+static __init int kvm_alloc_cpumask(void)
+{
+ int cpu;
+
+ if (!kvm_para_available() || nopv)
+ return 0;
+
+ if (pv_tlb_flush_supported() || pv_ipi_supported())
+ for_each_possible_cpu(cpu) {
+ zalloc_cpumask_var_node(per_cpu_ptr(&__pv_cpu_mask, cpu),
+ GFP_KERNEL, cpu_to_node(cpu));
+ }
+
+ return 0;
+}
+arch_initcall(kvm_alloc_cpumask);
+
+#endif
+
static void __init kvm_guest_init(void)
{
int i;
@@ -653,21 +671,21 @@ static void __init kvm_guest_init(void)
pv_ops.time.steal_clock = kvm_steal_clock;
}
+ if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
+ apic_set_eoi_write(kvm_guest_apic_eoi_write);
+
+ if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT) && kvmapf) {
+ static_branch_enable(&kvm_async_pf_enabled);
+ alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, asm_sysvec_kvm_asyncpf_interrupt);
+ }
+
+#ifdef CONFIG_SMP
if (pv_tlb_flush_supported()) {
pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
pv_ops.mmu.tlb_remove_table = tlb_remove_table;
pr_info("KVM setup pv remote TLB flush\n");
}
- if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
- apic_set_eoi_write(kvm_guest_apic_eoi_write);
-
- if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT) && kvmapf) {
- static_branch_enable(&kvm_async_pf_enabled);
- alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, asm_sysvec_kvm_asyncpf_interrupt);
- }
-
-#ifdef CONFIG_SMP
smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
if (pv_sched_yield_supported()) {
smp_ops.send_call_func_ipi = kvm_smp_send_call_func_ipi;
@@ -734,7 +752,7 @@ static uint32_t __init kvm_detect(void)
static void __init kvm_apic_init(void)
{
-#if defined(CONFIG_SMP)
+#ifdef CONFIG_SMP
if (pv_ipi_supported())
kvm_setup_pv_ipi();
#endif
@@ -794,31 +812,6 @@ static __init int activate_jump_labels(void)
}
arch_initcall(activate_jump_labels);
-static __init int kvm_alloc_cpumask(void)
-{
- int cpu;
- bool alloc = false;
-
- if (!kvm_para_available() || nopv)
- return 0;
-
- if (pv_tlb_flush_supported())
- alloc = true;
-
-#if defined(CONFIG_SMP)
- if (pv_ipi_supported())
- alloc = true;
-#endif
-
- if (alloc)
- for_each_possible_cpu(cpu) {
- zalloc_cpumask_var_node(per_cpu_ptr(&__pv_cpu_mask, cpu),
- GFP_KERNEL, cpu_to_node(cpu));
- }
-
- return 0;
-}
-arch_initcall(kvm_alloc_cpumask);
#ifdef CONFIG_PARAVIRT_SPINLOCKS
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