From: Hou Wenlong Date: Thu, 30 Oct 2025 19:15:28 +0000 (-0700) Subject: KVM: x86: Don't disable IRQs when unregistering user-return notifier X-Git-Tag: v6.19-rc1~103^2~9^2~34 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=995d504100cf66d846461133f8862b483295f995;p=thirdparty%2Flinux.git KVM: x86: Don't disable IRQs when unregistering user-return notifier Remove the code to disable IRQs when unregistering KVM's user-return notifier now that KVM doesn't invoke kvm_on_user_return() when disabling virtualization via IPI function call, i.e. now that there's no need to guard against re-entrancy via IPI callback. Note, disabling IRQs has largely been unnecessary since commit a377ac1cd9d7b ("x86/entry: Move user return notifier out of loop") moved fire_user_return_notifiers() into the section with IRQs disabled. In doing so, the commit somewhat inadvertently fixed the underlying issue that was papered over by commit 1650b4ebc99d ("KVM: Disable irq while unregistering user notifier"). I.e. in practice, the code and comment has been stale since commit a377ac1cd9d7b. Signed-off-by: Hou Wenlong [sean: rewrite changelog after rebasing, drop lockdep assert] Reviewed-by: Kai Huang Link: https://patch.msgid.link/20251030191528.3380553-5-seanjc@google.com Signed-off-by: Sean Christopherson --- diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 3bc3d527f442a..97852f190720a 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -602,18 +602,10 @@ static void kvm_on_user_return(struct user_return_notifier *urn) struct kvm_user_return_msrs *msrs = container_of(urn, struct kvm_user_return_msrs, urn); struct kvm_user_return_msr_values *values; - unsigned long flags; - /* - * Disabling irqs at this point since the following code could be - * interrupted and executed through kvm_arch_disable_virtualization_cpu() - */ - local_irq_save(flags); - if (msrs->registered) { - msrs->registered = false; - user_return_notifier_unregister(urn); - } - local_irq_restore(flags); + msrs->registered = false; + user_return_notifier_unregister(urn); + for (slot = 0; slot < kvm_nr_uret_msrs; ++slot) { values = &msrs->values[slot]; if (values->host != values->curr) {