Re: [PATCH 1/2] KVM: Fix the build error

[Haiwei Li]

On 20/9/20 21:09, Paolo Bonzini wrote:
> On 14/09/20 11:11, lihaiwei.kernel@xxxxxxxxx wrote:
> > From: Haiwei Li <lihaiwei@xxxxxxxxxxx>
> >
> > When CONFIG_SMP is not set, an build error occurs with message "error:
> > use of undeclared identifier 'kvm_send_ipi_mask_allbutself'"
> >
> > Fixes: 0f990222108d ("KVM: Check the allocation of pv cpu mask", 2020-09-01)
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > Signed-off-by: Haiwei Li <lihaiwei@xxxxxxxxxxx>
> > ---
> >   arch/x86/kernel/kvm.c | 2 ++
> >   1 file changed, 2 insertions(+)
> >
> > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> > index 1b51b727b140..7e8be0421720 100644
> > --- a/arch/x86/kernel/kvm.c
> > +++ b/arch/x86/kernel/kvm.c
> > @@ -797,7 +797,9 @@ static __init int kvm_alloc_cpumask(void)
> >   			}
> >   		}
> >   
> > +#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;
> >   	return 0;
> >   
>
> If CONFIG_SMP is not set you don't need kvm_alloc_cpumask or
> pv_ops.mmu.flush_tlb_others at all.  Can you squash these two into the
> original patch and re-submit for 5.10?

Hi, Paolo

I'm a little confused. Function kvm_flush_tlb_others doesn't seem to be 
related to CONFIG_SMP.

And my patch like:

---
 arch/x86/kernel/kvm.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 9663ba31347c..1e5da6db519c 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -553,7 +553,6 @@ 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");
 }

@@ -619,6 +618,11 @@ 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)) {
+		native_flush_tlb_others(cpumask, info);
+		return;
+	}
+
 	cpumask_copy(flushmask, cpumask);
 	/*
 	 * We have to call flush only on online vCPUs. And
@@ -765,6 +769,14 @@ static __init int activate_jump_labels(void)
 }
 arch_initcall(activate_jump_labels);

+static void kvm_free_cpumask(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;
@@ -783,11 +795,20 @@ 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
 	return 0;
+
+zalloc_cpumask_fail:
+	kvm_free_cpumask();
+	return -ENOMEM;
 }
 arch_initcall(kvm_alloc_cpumask);

--
2.18.4

Do you have any suggestion? Thanks.

    Haiwei