From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7A97CC433FE for ; Wed, 2 Nov 2022 23:45:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230381AbiKBXpe (ORCPT ); Wed, 2 Nov 2022 19:45:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33586 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229823AbiKBXpP (ORCPT ); Wed, 2 Nov 2022 19:45:15 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DB9946455 for ; Wed, 2 Nov 2022 16:42:23 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 78C9361C83 for ; Wed, 2 Nov 2022 23:42:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A91A7C433D6; Wed, 2 Nov 2022 23:42:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1667432542; bh=455Cu4D71HuazAlAm2UNip7yTxEBIKjaFHgDNfbLmWA=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=cM3bUA4e1vObYJIurQAxk676Ktef1WfeT316vF3csdwIJBVYf2APZndJaA4vHqg8N 1HbLxDOpBrxSqpmaDZnpIrjYBllnchqaT08Xg58+YH/8jZLKxS1qPybhenacc9aaO1 f71dFmpch375i39ItJJFoeYvUEVSxCpqLDYGxMTwYx/ByOdgNsFlRdmgLOcrQt2MgX Na6BSERVVD/L3kKGVArbbnRKXUSPOblDD4PTDWkO2K6ozqyAXCUxEMQqsLHcVNdsTs ozQXfBggT/6bPhPUkvB3MG/UHHDw84dPuJmuaXZew0DTF9NE747vlQmw11nBM9BuVa IVsqho0j85Y6Q== Date: Wed, 2 Nov 2022 18:42:21 -0500 From: Bjorn Helgaas To: francisco.munoz.ruiz@linux.intel.com Cc: lorenzo.pieralisi@arm.com, jonathan.derrick@linux.dev, linux-pci@vger.kernel.org, Nirmal Patel , Alex Williamson , Myron Stowe Subject: Re: [PATCH V2] PCI: vmd: Fix secondary bus reset for Intel bridges Message-ID: <20221102234221.GA8153@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20221031214501.28279-1-francisco.munoz.ruiz@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org [+cc Alex, Myron] On Mon, Oct 31, 2022 at 02:45:01PM -0700, francisco.munoz.ruiz@linux.intel.com wrote: > From: Francisco Munoz > > The reset was never applied in the current implementation because Intel > Bridges owned by VMD are parentless. Internally, pci_reset_bus applies > a reset to the parent of the pci device supplied as argument, but in this > case it failed because there wasn't a parent. > > In more detail, this change allows the VMD driver to enumerate NVMe devices > in pass-through configurations when host reboots are performed. Commit id > “6aab5622296b990024ee67dd7efa7d143e7558d0” attempted to fix this, but > later we discovered that the code inside pci_reset_bus wasn’t triggering > secondary bus resets. Therefore, we updated the parameters passed to > it, and now NVMe SSDs attached to VMD bridges are properly enumerated in > VT-d pass-through scenarios. Did you mean "guest reboots" above? If the *host* reboots, I assume everybody (host and guests) starts over, so a reset wouldn't really apply. Is the scenario that the VMD device is passed through to a guest, and the guest OS is running vmd_probe() and vmd_enable_domain()? I thought VFIO already had something to reset devices between guests. But maybe this is different because from the point of view of VFIO, the pass-through happens only once, and during that single session, the guest OS reboots several times, so you want vmd_probe() to reset the downstream devices? Should this have a Fixes: tag for 6aab5622296b? s/pci/PCI/ above in English text. Also add "()" after function names. Use the typical 12-char SHA1 + subject citation, e.g., 6aab5622296b ("PCI: vmd: Clean up domain before enumeration"). > Signed-off-by: Francisco Munoz > Reviewed-by: Nirmal Patel > --- > drivers/pci/controller/vmd.c | 12 ++++++++++-- > 1 file changed, 10 insertions(+), 2 deletions(-) > > diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c > index e06e9f4fc50f..34d6ba675440 100644 > --- a/drivers/pci/controller/vmd.c > +++ b/drivers/pci/controller/vmd.c > @@ -859,8 +859,16 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features) > > pci_scan_child_bus(vmd->bus); > vmd_domain_reset(vmd); > - list_for_each_entry(child, &vmd->bus->children, node) > - pci_reset_bus(child->self); > + > + list_for_each_entry(child, &vmd->bus->children, node) { > + if (!list_empty(&child->devices)) { > + pci_reset_bus(list_first_entry(&child->devices, > + struct pci_dev, > + bus_list)); > + break; > + } > + } > + > pci_assign_unassigned_bus_resources(vmd->bus); > > /* > -- > 2.25.1 > > Hi Bjorn, > > I updated the commit message with more details. Hopefully, this will > clarify its purpose. > > Thanks, > Francisco.