From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out28-169.mail.aliyun.com (out28-169.mail.aliyun.com [115.124.28.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2D1E726057F; Fri, 12 Sep 2025 09:38:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.28.169 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757669915; cv=none; b=ny9dGViduJDwYF8IYhVSRb4zV87spzQVB1CHkOW2r4MPYtaPO3lE2hPm+7Rh247GLvcJHGcvFAU5sU4jdXJs25tc26LeDyLWSymaiegFjuv5h7SCF507YHoCsTMjfQxw4L4ujoLiMlG5uOupQ32iCX50Kqd3/0qWB2Iid420rbg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757669915; c=relaxed/simple; bh=Q4RsKfIzmyxzKp8K4v2h79QFNV2EsiC86mjT5cGWiGc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=NS2arZI+RjwZVx46ska9X3yqK4+boKK8MSRP4ZczJvuRGv6Hs2GOqlSA9pOiP1Q/RbXJjOgEIeVQLQ43aatgJLrf/nVdLNNfNa0prglPJz5927st7qsTPz8RkT8fXlzlwi6EszrU/UoxddgqtaTslluPRb3g4kIM5m8ZDpAZmlk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=antgroup.com; spf=pass smtp.mailfrom=antgroup.com; dkim=pass (1024-bit key) header.d=antgroup.com header.i=@antgroup.com header.b=HyxKJPCw; arc=none smtp.client-ip=115.124.28.169 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=antgroup.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=antgroup.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=antgroup.com header.i=@antgroup.com header.b="HyxKJPCw" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=antgroup.com; s=default; t=1757669903; h=Date:From:To:Subject:Message-ID:MIME-Version:Content-Type; bh=nNS8A+t9o8wvAOaFCUjxryhM3zoj/mewmNrjEY/7elc=; b=HyxKJPCwX0pd0Zr6JL/z1q/8lurhjI+tKih+teMhkFN/+UNPV4ROVqFT1fQVIDTj4bAwkWuU/6lEyetwqO4BO8img7IvtwCyQ3ea0x94N9wl+jCHWKqnTf7GvlBW+QDjdxFvY4IqtuHcqc1q1wN1vVx7YnfT4/v3d25N2Fn7bN0= Received: from localhost(mailfrom:houwenlong.hwl@antgroup.com fp:SMTPD_---.edVVvTr_1757669902 cluster:ay29) by smtp.aliyun-inc.com; Fri, 12 Sep 2025 17:38:22 +0800 Date: Fri, 12 Sep 2025 17:38:22 +0800 From: Hou Wenlong To: Chao Gao Cc: kvm@vger.kernel.org, Sean Christopherson , Paolo Bonzini , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , linux-kernel@vger.kernel.org Subject: Re: [PATCH] KVM: x86: Remove outdated comments and code in kvm_on_user_return() Message-ID: <20250912093822.GA10794@k08j02272.eu95sqa> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) On Fri, Sep 12, 2025 at 04:35:00PM +0800, Chao Gao wrote: > On Fri, Sep 12, 2025 at 03:35:29PM +0800, Hou Wenlong wrote: > >The commit a377ac1cd9d7b ("x86/entry: Move user return notifier out of > >loop") moved fire_user_return_notifiers() into the section with > >interrupts disabled, so the callback kvm_on_user_return() cannot be > >interrupted by kvm_arch_disable_virtualization_cpu() now. Therefore, > >remove the outdated comments and local_irq_save()/local_irq_restore() > >code in kvm_on_user_return(). > > > >Signed-off-by: Hou Wenlong > >--- > > arch/x86/kvm/x86.c | 16 +++++----------- > > 1 file changed, 5 insertions(+), 11 deletions(-) > > > >diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > >index 33fba801b205..10afbacb1851 100644 > >--- a/arch/x86/kvm/x86.c > >+++ b/arch/x86/kvm/x86.c > >@@ -568,18 +568,12 @@ 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); > >+ lockdep_assert_irqs_disabled(); > > kvm_offline_cpu() may call into this function. But I am not sure if interrupts > are disabled in that path. > Thanks for pointing that out. I see that interrupts are enabled in the callback during the CPU offline test. I'll remove the lockdep_assert_irqs_disabled() here. > Documentation/core-api/cpu_hotplug.rst says that callbacks in the ONLINE section > are invoked with interrupts and preemption enabled. > > >+ > >+ 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) { > >-- > >2.31.1 > > > >