From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-181.mta1.migadu.com (out-181.mta1.migadu.com [95.215.58.181]) (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 043CD22687A for ; Thu, 20 Mar 2025 18:14:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.181 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742494489; cv=none; b=SMFaPcc8mOYs7FyUocgoMex+O7L3jJwG+8xvjR8hSIYPh2nGM1n+xYtNRcwT4Oxt0ErvjCXzsc7ZxewgysoJLMR70eGKtDsMuXg6tGpbxdUHt7estoiyuvYQYJa0BxOXMvQLHiJiIaAuiHQ3uMOujDLRTwSmXu1W1RKymafbWW4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742494489; c=relaxed/simple; bh=eHSnvQ6XhTYWAELznlpd0nObhNjlz62IdHaH+ijNn74=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=JbsUetSazI0VZbb/ZAB61hczJGzYKQ39jxvl7TcwJjidprhULDU3b1XZ/O8ilgsHHzc6PvCW9pUvGIK92V4nMFsla1hgk2aNN5ZpjPuEXsdI9k8Og22CP+/joMMy1CeLL2qIdYpwnbBXI6MVmp/CkVn8zzcjgZk3Ez3hx55qy68= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=LIgZL3UD; arc=none smtp.client-ip=95.215.58.181 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="LIgZL3UD" Date: Thu, 20 Mar 2025 18:14:29 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1742494474; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=g2IOmTqSF8VusdmE8MxtCc32BNiyhroRu8EGEaXViXs=; b=LIgZL3UD90N22INzZ79F/FPzmDaP+LUXj4N/xLoR5oBlA90P1ZCl0xgXcmDwPzYdTLByfz uTJ4Su47fkYozmqg/kjY6gEzkg+WVksySdFEx6IVMO0ovaPZduK9n7Xo0t7jqnrhMw4gMD cFG2mgUW71l7taAI9OjyBpFsdRyXTK8= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Yosry Ahmed To: Sean Christopherson Cc: Paolo Bonzini , kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 3/3] KVM: x86: Add a module param to control and enumerate device posted IRQs Message-ID: References: <20250320142022.766201-1-seanjc@google.com> <20250320142022.766201-4-seanjc@google.com> Precedence: bulk X-Mailing-List: kvm@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: X-Migadu-Flow: FLOW_OUT On Thu, Mar 20, 2025 at 10:59:19AM -0700, Sean Christopherson wrote: > On Thu, Mar 20, 2025, Sean Christopherson wrote: > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > > index f76d655dc9a8..e7eb2198db26 100644 > > --- a/arch/x86/kvm/x86.c > > +++ b/arch/x86/kvm/x86.c > > @@ -227,6 +227,10 @@ EXPORT_SYMBOL_GPL(allow_smaller_maxphyaddr); > > bool __read_mostly enable_apicv = true; > > EXPORT_SYMBOL_GPL(enable_apicv); > > > > +bool __read_mostly enable_device_posted_irqs = true; > > +module_param(enable_device_posted_irqs, bool, 0444); > > +EXPORT_SYMBOL_GPL(enable_device_posted_irqs); > > + > > const struct _kvm_stats_desc kvm_vm_stats_desc[] = { > > KVM_GENERIC_VM_STATS(), > > STATS_DESC_COUNTER(VM, mmu_shadow_zapped), > > @@ -9772,6 +9776,9 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops) > > if (r != 0) > > goto out_mmu_exit; > > > > + enable_device_posted_irqs &= enable_apicv && > > + irq_remapping_cap(IRQ_POSTING_CAP); > > Drat, this is flawed. Putting the module param in kvm.ko means that loading > kvm.ko with enable_device_posted_irqs=true, but a vendor module with APICv/AVIC > disabled, leaves enable_device_posted_irqs disabled for the lifetime of kvm.ko. > I.e. reloading the vendor module with APICv/AVIC enabled can't enable device > posted IRQs. > > Option #1 is to do what we do for enable_mmio_caching, and snapshot userspace's > desire. > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index e7eb2198db26..c84ad9109108 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -228,6 +228,7 @@ bool __read_mostly enable_apicv = true; > EXPORT_SYMBOL_GPL(enable_apicv); > > bool __read_mostly enable_device_posted_irqs = true; > +bool __ro_after_init allow_device_posted_irqs; > module_param(enable_device_posted_irqs, bool, 0444); > EXPORT_SYMBOL_GPL(enable_device_posted_irqs); > > @@ -9776,8 +9777,8 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops) > if (r != 0) > goto out_mmu_exit; > > - enable_device_posted_irqs &= enable_apicv && > - irq_remapping_cap(IRQ_POSTING_CAP); > + enable_device_posted_irqs = allow_device_posted_irqs && enable_apicv && > + irq_remapping_cap(IRQ_POSTING_CAP); > > kvm_ops_update(ops); > > @@ -14033,6 +14034,8 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_rmp_fault); > > static int __init kvm_x86_init(void) > { > + allow_device_posted_irqs = enable_device_posted_irqs; > + > kvm_init_xstate_sizes(); > > kvm_mmu_x86_module_init(); > > > Option #2 is to shove the module param into vendor code, but leave the variable > in kvm.ko, like we do for enable_apicv. > > I'm leaning toward option #2, as it's more flexible, arguably more intuitive, and > doesn't prevent putting the logic in kvm_x86_vendor_init(). +1, option #1 seems a bit confusing to me.