On 20/9/4 17:53, Vitaly Kuznetsov wrote:
Haiwei Li <lihaiwei.kernel@xxxxxxxxx> writes:
On 20/9/3 18:39, Vitaly Kuznetsov wrote:
Haiwei Li <lihaiwei.kernel@xxxxxxxxx> writes:
From: Haiwei Li <lihaiwei@xxxxxxxxxxx>
check the allocation of per-cpu __pv_cpu_mask. Initialize ops only when
successful.
Signed-off-by: Haiwei Li <lihaiwei@xxxxxxxxxxx>
---
arch/x86/kernel/kvm.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 08320b0b2b27..d3c062e551d7 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -555,7 +555,6 @@ static void kvm_send_ipi_mask_allbutself(const
struct cpumask *mask, int vector)
static void kvm_setup_pv_ipi(void)
{
apic->send_IPI_mask = kvm_send_ipi_mask;
- apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
pr_info("setup PV IPIs\n");
}
@@ -654,7 +653,6 @@ 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");
}
@@ -767,6 +765,14 @@ static __init int activate_jump_labels(void)
}
arch_initcall(activate_jump_labels);
+static void kvm_free_pv_cpu_mask(void)
+{
+ unsigned int cpu;
+
+ for_each_possible_cpu(cpu)
+ free_cpumask_var(per_cpu(__pv_cpu_mask, cpu));
+}
+
static __init int kvm_alloc_cpumask(void)
{
int cpu;
@@ -785,11 +791,21 @@ static __init int kvm_alloc_cpumask(void)
if (alloc)
for_each_possible_cpu(cpu) {
- zalloc_cpumask_var_node(per_cpu_ptr(&__pv_cpu_mask, cpu),
- GFP_KERNEL, cpu_to_node(cpu));
+ if (!zalloc_cpumask_var_node(
+ per_cpu_ptr(&__pv_cpu_mask, cpu),
+ GFP_KERNEL, cpu_to_node(cpu)))
+ goto zalloc_cpumask_fail;
}
+#if defined(CONFIG_SMP)
+ apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
+#endif
+ pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
This is too late I'm afraid. If I'm not mistaken PV patching happens
earlier, so .init.guest_late_init (kvm_guest_init()) is good and
arch_initcall() is bad.
.init.guest_late_init (kvm_guest_init()) is called before
arch_initcall() and kvm_flush_tlb_others && kvm_send_ipi_mask_allbutself
rely on __pv_cpu_mask. So, i can not put this assign in kvm_guest_init().
Have you checked that with this patch kvm_flush_tlb_others() is still
being called?
yes. I add a printk and i get the log.
This is weird. I do the following on top of your patch:
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index d3c062e551d7..f441209ff0a4 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -620,6 +620,8 @@ static void kvm_flush_tlb_others(const struct cpumask *cpumask,
struct kvm_steal_time *src;
struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_cpu_mask);
+ trace_printk("PV TLB flush %d CPUs\n", cpumask_weight(cpumask));
+
cpumask_copy(flushmask, cpumask);
/*
* We have to call flush only on online vCPUs. And
With your patch I don't see any calls:
# grep -c -v '^#' /sys/kernel/debug/tracing/trace
0
with your patch reverted I see them:
# grep -c -v '^#' /sys/kernel/debug/tracing/trace
4571
I just retested. You are right. I'm sorry.
Actually, there is no need to assign kvm_flush_tlb_others() so late. We
can always check if __pv_cpu_mask was allocated and revert back to the
architectural path if not.
I am sorry i don't really understand. Can you explain in more detail? Thx.
I mean we can always call e.g. kvm_flush_tlb_others(), even if (very
unlikely) the mask wasn't allocated. We just need to check for
that. Something like (completely untested):
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index d3c062e551d7..e3676cdee6a2 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -620,6 +620,11 @@ static void kvm_flush_tlb_others(const struct cpumask *cpumask,
struct kvm_steal_time *src;
struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_cpu_mask);
+ if (unlikely(!flushmask)) {
+ flushmask = cpumask;
+ goto do_native;
+ }
+
I see. I appreciate your patience and kindness.
I will send a new version.
cpumask_copy(flushmask, cpumask);
/*
* We have to call flush only on online vCPUs. And
@@ -635,6 +640,7 @@ static void kvm_flush_tlb_others(const struct cpumask *cpumask,
}
}
+do_native:
native_flush_tlb_others(flushmask, info);
}
return 0;
+
+zalloc_cpumask_fail:
+ kvm_free_pv_cpu_mask();
+ return -ENOMEM;
}
arch_initcall(kvm_alloc_cpumask);
--
2.18.4
