From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ale.deltatee.com ([207.54.116.67]:45146 "EHLO ale.deltatee.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729980AbeGQSXw (ORCPT ); Tue, 17 Jul 2018 14:23:52 -0400 To: Alex Williamson Cc: linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-doc@vger.kernel.org, Stephen Bates , Christoph Hellwig , Bjorn Helgaas , Jonathan Corbet , Ingo Molnar , Thomas Gleixner , "Paul E. McKenney" , Marc Zyngier , Kai-Heng Feng , Frederic Weisbecker , Dan Williams , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Benjamin Herrenschmidt , =?UTF-8?Q?Christian_K=c3=b6nig?= , Matthew Wilcox References: <20180717170204.30470-1-logang@deltatee.com> <20180717170204.30470-5-logang@deltatee.com> <20180717114848.2914d547@t450s.home> From: Logan Gunthorpe Message-ID: Date: Tue, 17 Jul 2018 11:49:22 -0600 MIME-Version: 1.0 In-Reply-To: <20180717114848.2914d547@t450s.home> Content-Type: text/plain; charset=utf-8 Subject: Re: [PATCH v7 4/4] PCI: Introduce the disable_acs_redir parameter Sender: linux-pci-owner@vger.kernel.org List-ID: On 17/07/18 11:48 AM, Alex Williamson wrote: > On Tue, 17 Jul 2018 11:02:04 -0600 > Logan Gunthorpe wrote: > >> In order to support P2P traffic on a segment of the PCI hierarchy, >> we must be able to disable the ACS redirect bits for select >> PCI bridges. The bridges must be selected before the devices are >> discovered by the kernel and the IOMMU groups created. Therefore, >> a kernel command line parameter is created to specify devices >> which must have their ACS bits disabled. >> >> The new parameter takes a list of devices separated by a semicolon. >> Each device specified will have it's ACS redirect bits disabled. >> This is similar to the existing 'resource_alignment' parameter. >> >> The ACS Request P2P Request Redirect, P2P Completion Redirect and P2P >> Egress Control bits are disabled which is sufficient to always allow >> passing P2P traffic uninterrupted. The bits are set after the kernel >> (optionally) enables the ACS bits itself. It is also done regardless of >> whether the kernel sets the bits or not seeing some BIOS firmware is known >> to set the bits on boot. >> >> If the user tries to disable the ACS redirct for a device without the >> ACS capability, a warning is printed to dmesg. >> >> Signed-off-by: Logan Gunthorpe >> Reviewed-by: Stephen Bates >> Acked-by: Christian König >> --- >> Documentation/admin-guide/kernel-parameters.txt | 9 +++ >> drivers/pci/pci.c | 76 ++++++++++++++++++++++++- >> 2 files changed, 83 insertions(+), 2 deletions(-) > > Thanks for the re-spins! > > Reviewed-by: Alex Williamson Thanks for all the thorough review! Logan