Commit 8a9442f4 authored by Wanpeng Li's avatar Wanpeng Li Committed by Paolo Bonzini

KVM: Pre-allocate 1 cpumask variable per cpu for both pv tlb and pv ipis

Nick Desaulniers Reported:

  When building with:
  $ make CC=clang arch/x86/ CFLAGS=-Wframe-larger-than=1000
  The following warning is observed:
  arch/x86/kernel/kvm.c:494:13: warning: stack frame size of 1064 bytes in
  function 'kvm_send_ipi_mask_allbutself' [-Wframe-larger-than=]
  static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int
  vector)
              ^
  Debugging with:
  https://github.com/ClangBuiltLinux/frame-larger-than
  via:
  $ python3 frame_larger_than.py arch/x86/kernel/kvm.o \
    kvm_send_ipi_mask_allbutself
  points to the stack allocated `struct cpumask newmask` in
  `kvm_send_ipi_mask_allbutself`. The size of a `struct cpumask` is
  potentially large, as it's CONFIG_NR_CPUS divided by BITS_PER_LONG for
  the target architecture. CONFIG_NR_CPUS for X86_64 can be as high as
  8192, making a single instance of a `struct cpumask` 1024 B.

This patch fixes it by pre-allocate 1 cpumask variable per cpu and use it for
both pv tlb and pv ipis..
Reported-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Acked-by: default avatarNick Desaulniers <ndesaulniers@google.com>
Reviewed-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: default avatarWanpeng Li <wanpengli@tencent.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent a262bca3
...@@ -432,6 +432,8 @@ static bool pv_tlb_flush_supported(void) ...@@ -432,6 +432,8 @@ static bool pv_tlb_flush_supported(void)
kvm_para_has_feature(KVM_FEATURE_STEAL_TIME)); kvm_para_has_feature(KVM_FEATURE_STEAL_TIME));
} }
static DEFINE_PER_CPU(cpumask_var_t, __pv_cpu_mask);
#ifdef CONFIG_SMP #ifdef CONFIG_SMP
static bool pv_ipi_supported(void) static bool pv_ipi_supported(void)
...@@ -510,12 +512,12 @@ static void kvm_send_ipi_mask(const struct cpumask *mask, int vector) ...@@ -510,12 +512,12 @@ static void kvm_send_ipi_mask(const struct cpumask *mask, int vector)
static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int vector) static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int vector)
{ {
unsigned int this_cpu = smp_processor_id(); unsigned int this_cpu = smp_processor_id();
struct cpumask new_mask; struct cpumask *new_mask = this_cpu_cpumask_var_ptr(__pv_cpu_mask);
const struct cpumask *local_mask; const struct cpumask *local_mask;
cpumask_copy(&new_mask, mask); cpumask_copy(new_mask, mask);
cpumask_clear_cpu(this_cpu, &new_mask); cpumask_clear_cpu(this_cpu, new_mask);
local_mask = &new_mask; local_mask = new_mask;
__send_ipi_mask(local_mask, vector); __send_ipi_mask(local_mask, vector);
} }
...@@ -595,7 +597,6 @@ static void __init kvm_apf_trap_init(void) ...@@ -595,7 +597,6 @@ static void __init kvm_apf_trap_init(void)
update_intr_gate(X86_TRAP_PF, async_page_fault); update_intr_gate(X86_TRAP_PF, async_page_fault);
} }
static DEFINE_PER_CPU(cpumask_var_t, __pv_tlb_mask);
static void kvm_flush_tlb_others(const struct cpumask *cpumask, static void kvm_flush_tlb_others(const struct cpumask *cpumask,
const struct flush_tlb_info *info) const struct flush_tlb_info *info)
...@@ -603,7 +604,7 @@ static void kvm_flush_tlb_others(const struct cpumask *cpumask, ...@@ -603,7 +604,7 @@ static void kvm_flush_tlb_others(const struct cpumask *cpumask,
u8 state; u8 state;
int cpu; int cpu;
struct kvm_steal_time *src; struct kvm_steal_time *src;
struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_tlb_mask); struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_cpu_mask);
cpumask_copy(flushmask, cpumask); cpumask_copy(flushmask, cpumask);
/* /*
...@@ -642,6 +643,7 @@ static void __init kvm_guest_init(void) ...@@ -642,6 +643,7 @@ static void __init kvm_guest_init(void)
if (pv_tlb_flush_supported()) { if (pv_tlb_flush_supported()) {
pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others; pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
pv_ops.mmu.tlb_remove_table = tlb_remove_table; 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)) if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
...@@ -748,24 +750,31 @@ static __init int activate_jump_labels(void) ...@@ -748,24 +750,31 @@ static __init int activate_jump_labels(void)
} }
arch_initcall(activate_jump_labels); arch_initcall(activate_jump_labels);
static __init int kvm_setup_pv_tlb_flush(void) static __init int kvm_alloc_cpumask(void)
{ {
int cpu; int cpu;
bool alloc = false;
if (!kvm_para_available() || nopv) if (!kvm_para_available() || nopv)
return 0; return 0;
if (pv_tlb_flush_supported()) { 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) { for_each_possible_cpu(cpu) {
zalloc_cpumask_var_node(per_cpu_ptr(&__pv_tlb_mask, cpu), zalloc_cpumask_var_node(per_cpu_ptr(&__pv_cpu_mask, cpu),
GFP_KERNEL, cpu_to_node(cpu)); GFP_KERNEL, cpu_to_node(cpu));
} }
pr_info("KVM setup pv remote TLB flush\n");
}
return 0; return 0;
} }
arch_initcall(kvm_setup_pv_tlb_flush); arch_initcall(kvm_alloc_cpumask);
#ifdef CONFIG_PARAVIRT_SPINLOCKS #ifdef CONFIG_PARAVIRT_SPINLOCKS
......
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