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

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Date:   Wed, 23 Sep 2020 13:02:17 +0800
From:   Haiwei Li <lihaiwei.kernel@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, x86@...nel.org
Cc:     sean.j.christopherson@...el.com, vkuznets@...hat.com,
        wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        lihaiwei@...cent.com, kernel test robot <lkp@...el.com>
Subject: Re: [PATCH 1/2] KVM: Fix the build error

On 20/9/20 21:09, Paolo Bonzini wrote:
> On 14/09/20 11:11, lihaiwei.kernel@...il.com wrote:
>> From: Haiwei Li <lihaiwei@...cent.com>
>>
>> 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@...el.com>
>> Signed-off-by: Haiwei Li <lihaiwei@...cent.com>
>> ---
>>   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