[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [PATCH 00/15] perf: KVM: Fix, optimize, and clean up callbacks
On 27/8/2021 3:44 pm, Peter Zijlstra wrote: On Fri, Aug 27, 2021 at 02:52:25PM +0800, Like Xu wrote:+ STATIC BRANCH/CALL friends. On 27/8/2021 8:57 am, Sean Christopherson wrote:This started out as a small series[1] to fix a KVM bug related to Intel PT interrupt handling and snowballed horribly. The main problem being addressed is that the perf_guest_cbs are shared by all CPUs, can be nullified by KVM during module unload, and are not protected against concurrent access from NMI context.Shouldn't this be a generic issue of the static_call() usage ? At the beginning, we set up the static entry assuming perf_guest_cbs != NULL: if (perf_guest_cbs && perf_guest_cbs->handle_intel_pt_intr) { static_call_update(x86_guest_handle_intel_pt_intr, perf_guest_cbs->handle_intel_pt_intr); } and then we unset the perf_guest_cbs and do the static function call like this: DECLARE_STATIC_CALL(x86_guest_handle_intel_pt_intr, *(perf_guest_cbs->handle_intel_pt_intr)); static int handle_pmi_common(struct pt_regs *regs, u64 status) { ... if (!static_call(x86_guest_handle_intel_pt_intr)()) intel_pt_interrupt(); ... }You just have to make sure all static_call() invocations that started before unreg are finished before continuing with the unload. synchronize_rcu() can help with that. Do you mean something like that: diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 64e310ff4f3a..e7d310af7509 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -8465,6 +8465,7 @@ void kvm_arch_exit(void) #endif kvm_lapic_exit(); perf_unregister_guest_info_callbacks(&kvm_guest_cbs); + synchronize_rcu(); if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) cpufreq_unregister_notifier(&kvmclock_cpufreq_notifier_block, diff --git a/kernel/events/core.c b/kernel/events/core.c index e466fc8176e1..63ae56c5d133 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6508,6 +6508,7 @@ EXPORT_SYMBOL_GPL(perf_register_guest_info_callbacks); int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs) { perf_guest_cbs = NULL; + arch_perf_update_guest_cbs(); return 0; } EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks); This is module unload 101. Nothing specific to static_call().
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