Messages in this thread | | | Date | Tue, 23 Aug 2022 10:26:09 +0800 | From | Chao Gao <> | Subject | Re: [RFC PATCH 03/18] KVM: Drop kvm_count_lock and instead protect kvm_usage_count with kvm_lock |
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On Fri, Aug 19, 2022 at 11:00:09PM -0700, isaku.yamahata@intel.com wrote: >From: Isaku Yamahata <isaku.yamahata@intel.com> > >Because kvm_count_lock unnecessarily complicates the KVM locking convention >Drop kvm_count_lock and instead protect kvm_usage_count with kvm_lock for >simplicity. > >Opportunistically add some comments on locking. > >Suggested-by: Sean Christopherson <seanjc@google.com> >Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> >--- > static cpumask_var_t cpus_hardware_enabled; >@@ -4999,6 +4998,8 @@ static void hardware_enable_nolock(void *junk) > int cpu = raw_smp_processor_id(); > int r; > >+ WARN_ON_ONCE(preemptible()); >+ > if (cpumask_test_cpu(cpu, cpus_hardware_enabled)) > return; > >@@ -5015,10 +5016,10 @@ static void hardware_enable_nolock(void *junk) > > static int kvm_starting_cpu(unsigned int cpu) > { >- raw_spin_lock(&kvm_count_lock); >+ mutex_lock(&kvm_lock);
kvm_starting_cpu() is called with interrupt disabled. So we cannot use sleeping locks (e.g., mutex) here.
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