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authorWanpeng Li <wanpengli@tencent.com>2020-02-18 09:08:24 +0800
committerPaolo Bonzini <pbonzini@redhat.com>2020-02-28 10:34:25 +0100
commit8a9442f49c72bde43f982e53b74526ac37d3565b (patch)
tree26afe2e6c08863d26927695bdd4208cab4e28ad2
parenta262bca3aba03f0696995beb223c610e47533db3 (diff)
downloadlinux-sh-8a9442f49c72bde43f982e53b74526ac37d3565b.tar.gz
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: Nick Desaulniers <ndesaulniers@google.com> Acked-by: Nick Desaulniers <ndesaulniers@google.com> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Nick Desaulniers <ndesaulniers@google.com> Signed-off-by: Wanpeng Li <wanpengli@tencent.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kernel/kvm.c33
1 files changed, 21 insertions, 12 deletions
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 7bc0fff3f8e6..6efe0410fb72 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -432,6 +432,8 @@ static bool pv_tlb_flush_supported(void)
kvm_para_has_feature(KVM_FEATURE_STEAL_TIME));
}
+static DEFINE_PER_CPU(cpumask_var_t, __pv_cpu_mask);
+
#ifdef CONFIG_SMP
static bool pv_ipi_supported(void)
@@ -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)
{
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;
- cpumask_copy(&new_mask, mask);
- cpumask_clear_cpu(this_cpu, &new_mask);
- local_mask = &new_mask;
+ cpumask_copy(new_mask, mask);
+ cpumask_clear_cpu(this_cpu, new_mask);
+ local_mask = new_mask;
__send_ipi_mask(local_mask, vector);
}
@@ -595,7 +597,6 @@ static void __init kvm_apf_trap_init(void)
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,
const struct flush_tlb_info *info)
@@ -603,7 +604,7 @@ static void kvm_flush_tlb_others(const struct cpumask *cpumask,
u8 state;
int cpu;
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);
/*
@@ -642,6 +643,7 @@ static void __init kvm_guest_init(void)
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))
@@ -748,24 +750,31 @@ static __init int activate_jump_labels(void)
}
arch_initcall(activate_jump_labels);
-static __init int kvm_setup_pv_tlb_flush(void)
+static __init int kvm_alloc_cpumask(void)
{
int cpu;
+ bool alloc = false;
if (!kvm_para_available() || nopv)
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) {
- 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));
}
- pr_info("KVM setup pv remote TLB flush\n");
- }
return 0;
}
-arch_initcall(kvm_setup_pv_tlb_flush);
+arch_initcall(kvm_alloc_cpumask);
#ifdef CONFIG_PARAVIRT_SPINLOCKS