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.ker...@gmail.com wrote:
From: Haiwei Li <lihai...@tencent.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 <l...@intel.com>
Signed-off-by: Haiwei Li <lihai...@tencent.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