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 E4AB6C5DF62 for ; Tue, 25 Jan 2022 23:55:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235027AbiAYXzI (ORCPT ); Tue, 25 Jan 2022 18:55:08 -0500 Received: from mga14.intel.com ([192.55.52.115]:33207 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235023AbiAYXzI (ORCPT ); Tue, 25 Jan 2022 18:55:08 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1643154907; x=1674690907; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=4TSE6Zm6S6tEQ74B0UfqdCJcrocrR2hMUptoML8fanw=; b=YJ9/vKeMmaJrRCdXSej+/LmNNYDt86JiRkgrtXirrkA+d+npg6XYUDDP ZN29zu8vnnKOBbxm09yuqlJTdawfagPAOQYtx4X9xQ7WyCdmPS19bSxX2 woIlLRUWifM3vl8gEyLVAoAkIhrl9c9Tiz5wWZZl+Ga99CJubrpxfNiiq 6N/g5DUp9HvS4Gd46SSsYa6rmfPSluHK1IrjvqrTbX2J3WQkVqGu7lZjV r2WVARnoNqdgaw2FSw5Iz8vaq+pB876hvXdO4VRozUFtvvpx7YjpjpyCq CXiHzsRL9KCTQgz27UG716jg2uIah6TUOQcnA3uRfmcthLpTnKARgf2SI Q==; X-IronPort-AV: E=McAfee;i="6200,9189,10238"; a="246661564" X-IronPort-AV: E=Sophos;i="5.88,316,1635231600"; d="scan'208";a="246661564" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Jan 2022 15:55:06 -0800 X-IronPort-AV: E=Sophos;i="5.88,316,1635231600"; d="scan'208";a="563229916" Received: from jungjunk-mobl1.amr.corp.intel.com (HELO intel.com) ([10.252.128.93]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Jan 2022 15:55:05 -0800 Date: Tue, 25 Jan 2022 15:55:03 -0800 From: Ben Widawsky To: Jonathan Cameron Cc: qemu-devel@nongnu.org, Marcel Apfelbaum , "Michael S . Tsirkin" , Igor Mammedov , linux-cxl@vger.kernel.org, Alex =?utf-8?Q?Benn=C3=A9e?= , Peter Maydell , linuxarm@huawei.com, Shameerali Kolothum Thodi , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Saransh Gupta1 , Shreyas Shah , Chris Browy , Samarth Saxena , Dan Williams Subject: Re: [PATCH v4 00/42] CXl 2.0 emulation Support Message-ID: <20220125235503.crqfbyjtpikj3cjn@intel.com> References: <20220124171705.10432-1-Jonathan.Cameron@huawei.com> <20220125191806.ifbv2fuj2bik44zw@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220125191806.ifbv2fuj2bik44zw@intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org On 22-01-25 11:18:08, Ben Widawsky wrote: > Really awesome work Jonathan. Dan and I are wrapping up some of the kernel bits, > so all I'll do for now is try to run this, but I hope to be able to review the > parts I'm familiar with at least. > > On 22-01-24 17:16:23, Jonathan Cameron wrote: > > Previous version was RFC v3: CXL 2.0 Support. > > No longer an RFC as I would consider the vast majority of this > > to be ready for detailed review. There are still questions called > > out in some patches however. > > > > Looking in particular for: > > * Review of the PCI interactions > > * x86 and ARM machine interactions (particularly the memory maps) > > * Review of the interleaving approach - is the basic idea > > acceptable? > > * Review of the command line interface. > > * CXL related review welcome but much of that got reviewed > > in earlier versions and hasn't changed substantially. > > > > Main changes: > > * The CXL fixed memory windows are now instantiated via a > > -cxl-fixed-memory-window command line option. As they are host level > > entities, not associated with a particular hardware entity a top > > level parameter seems the most natural way to describe them. > > This is also much closer to how it works on a real host than the > > previous assignment of a physical address window to all components > > along the CXL path. > > Excellent. > > > * Dynamic host memory physical address space allocation both for > > the CXL host bridge MMIO space and the CFMWS windows. > > I thought I had done the host bridge MMIO, but perhaps I was mistaken. Either > way, this is an important step to support all platforms more generally. > > > * Interleaving support (based loosely on Philippe Mathieu-Daudé's > > earlier work on an interleaved memory device). Note this is rudimentary > > and low performance but it may be sufficient for test purposes. > > I'll have to look at this further. I had some thoughts about how we might make > this fast, but it would be more of fake interleaving. How low is "low"? > > > * Additional PCI and memory related utility functions needed for the > > interleaving. > > * Various minor cleanup and increase in scope of tests. > > * For now dropped the support for presenting CXL type 3 devices > > as memory devices in various QEMU interfaces. > > What are the downsides to this? I only used the memory interface originally > because it seemed like a natural fit, but looking back I'm not sure we gain > much (though my memory is very lossy). > > > * Dropped the patch letting UID be different from bus_nr. Whilst > > it may be a useful thing to have, we don't need it for this series > > and so should be handled separately. > > > > I've called out patches with major changes by marking them as > > co-developed or introducing them as new patches. The original > > memory window code has been dropped > > > > After discussions at plumbers and more recently on the mailing list > > it was clear that there was interest in getting emulation for CXL 2.0 > > upstream in QEMU. This version resolves many of the outstanding issues > > and enables the following features: > > > > * Support on both x86/pc and ARM/virt with relevant ACPI tables > > generated in QEMU. > > * Host bridge based on the existing PCI Expander Bridge PXB. > > * CXL fixed memory windows, allowing host to describe interleaving > > across multiple CXL host bridges. > > * pxb-cxl CXL host bridge support including MMIO region for control > > and HDM (Host manage device memory - basically interleaving / routing) > > decoder configuration. > > * Basic CXL Root port support. > > * CXL Type 3 device support with persistent memory regions (backed by > > hostmem backend). > > * Pulled MAINTAINERS entry out to a separate patch and add myself as > > a co-maintainer at Ben's suggestion. > > > > Big TODOs: > > > > * Volatile memory devices (easy but it's more code so left for now). > > * Switch support. > > * Hotplug? May not need much but it's not tested yet! > > * More tests and tighter verification that values written to hardware > > are actually valid - stuff that real hardware would check. > > * Main host bridge support (not a priority for me...) > > I originally cared about this for the sake of making a system more realistic. I > now believe we should drop this entirely. > > > * Testing, testing and more testing. I have been running a basic > > set of ARM and x86 tests on this, but there is always room for > > more tests and greater automation. > > > > Why do we want QEMU emulation of CXL? > > > > As Ben stated in V3, QEMU support has been critical to getting OS > > software written given lack of availability of hardware supporting the > > latest CXL features (coupled with very high demand for support being > > ready in a timely fashion). What has become clear since Ben's v3 > > is that situation is a continuous one. Whilst we can't talk about > > them yet, CXL 3.0 features and OS support have been prototyped on > > top of this support and a lot of the ongoing kernel work is being > > tested against these patches. > > > > Other features on the qemu-list that build on these include PCI-DOE > > /CDAT support from the Avery Design team further showing how this > > code is useful. Whilst not directly related this is also the test > > platform for work on PCI IDE/CMA + related DMTF SPDM as CXL both > > utilizes and extends those technologies and is likely to be an early > > adopter. > > Refs: > > CMA Kernel: https://lore.kernel.org/all/20210804161839.3492053-1-Jonathan.Cameron@huawei.com/ > > CMA Qemu: https://lore.kernel.org/qemu-devel/1624665723-5169-1-git-send-email-cbrowy@avery-design.com/ > > DOE Qemu: https://lore.kernel.org/qemu-devel/1623329999-15662-1-git-send-email-cbrowy@avery-design.com/ > > > > > > As can be seen there is non trivial interaction with other areas of > > Qemu, particularly PCI and keeping this set up to date is proving > > a burden we'd rather do without :) > > > > Ben mentioned a few other good reasons in v3: > > https://lore.kernel.org/qemu-devel/20210202005948.241655-1-ben.widawsky@intel.com/ > > > > The evolution of this series perhaps leave it in a less than > > entirely obvious order and that may get tidied up in future postings. > > I'm also open to this being considered in bite sized chunks. What > > we have here is about what you need for it to be useful for testing > > currently kernel code. > > > > All comments welcome. > > > > Ben - I lifted one patch from your git tree that didn't have a > > Sign-off. hw/cxl/component Add a dumb HDM decoder handler > > Could you confirm you are happy for one to be added? > > Sure. > > > > > Example of new command line (with virt ITS patches ;) > > > > qemu-system-aarch64 -M virt,gic-version=3,cxl=on \ > > -m 4g,maxmem=8G,slots=8 \ > > ... > > -object memory-backend-file,id=cxl-mem1,share=on,mem-path=/tmp/cxltest.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-mem2,share=on,mem-path=/tmp/cxltest2.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-mem3,share=on,mem-path=/tmp/cxltest3.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-mem4,share=on,mem-path=/tmp/cxltest4.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-lsa1,share=on,mem-path=/tmp/lsa.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-lsa2,share=on,mem-path=/tmp/lsa2.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-lsa3,share=on,mem-path=/tmp/lsa3.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-lsa4,share=on,mem-path=/tmp/lsa4.raw,size=256M,align=256M \ > > Is align actually necessary here? > > > -object memory-backend-file,id=tt,share=on,mem-path=/tmp/tt.raw,size=1g \ > > Did you mean to put this in there? Is it somehow used internally? > > > -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \ > > -device pxb-cxl,bus_nr=222,bus=pcie.0,id=cxl.2 \ > > -device cxl-rp,port=0,bus=cxl.1,id=root_port13,chassis=0,slot=2 \ > > -device cxl-type3,bus=root_port13,memdev=cxl-mem1,lsa=cxl-lsa1,id=cxl-pmem0,size=256M \ > > -device cxl-rp,port=1,bus=cxl.1,id=root_port14,chassis=0,slot=3 \ > > -device cxl-type3,bus=root_port14,memdev=cxl-mem2,lsa=cxl-lsa2,id=cxl-pmem1,size=256M \ > > -device cxl-rp,port=0,bus=cxl.2,id=root_port15,chassis=0,slot=5 \ > > -device cxl-type3,bus=root_port15,memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem2,size=256M \ > > -device cxl-rp,port=1,bus=cxl.2,id=root_port16,chassis=0,slot=6 \ > > -device cxl-type3,bus=root_port16,memdev=cxl-mem4,lsa=cxl-lsa4,id=cxl-pmem3,size=256M \ > > -cxl-fixed-memory-window targets=cxl.1,size=4G,interleave-granularity=8k \ > > -cxl-fixed-memory-window targets=cxl.1,targets=cxl.2,size=4G,interleave-granularity=8k > > I assume interleave-ways is based on the number of targets. For testing purposes > it might be nice to add the flags as well (perhaps it's there). > This requires cxl=on machine arg now btw. > > > > First CFMWS suitable for 2 way interleave, the second for 4 way (2 way > > at host level and 2 way at the host bridge). > > targets= , multiple entries if range is disjoint. > > > > With Ben's CXL region patches (v3 shortly) plus fixes as discussed on list, > > Linux commands to bring up a 4 way interleave is: > > > > cd /sys/bus/cxl/devices/ > > region=$(cat decoder0.1/create_region) > > echo $region > decoder0.1/create_region > > ls -lh > > > > //Note the order of devices and adjust the following to make sure they > > //are in order across the 4 root ports. Easy to do in a tool, but > > //not easy to paste in a cover letter. > > > > cd region0.1\:0 > > echo 4 > interleave_ways > > echo mem2 > target0 > > echo mem3 > target1 > > echo mem0 > target2 > > echo mem1 > target3 > > echo $((1024<<20)) > size > > echo 4096 > interleave_granularity > > echo region0.1:0 > /sys/bus/cxl/drivers/cxl_region/bind > > > > Tested with devmem2 and files with known content. > > Kernel tree was based on previous version of the region patches > > from Ben with various fixes. As Dan just posted an updated version > > next job on my list is to test that. > > > > Thanks to Shameer for his help with reviewing the new stuff before > > posting. > > > > I'll post a git tree shortly for any who prefer that to lots > > of emails ;) > > > > Thanks, > > > > Jonathan > > Thanks again! > Ben > > [snip] > > 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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id AD6B7C5AC75 for ; Wed, 26 Jan 2022 00:14:43 +0000 (UTC) Received: from localhost ([::1]:55124 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1nCVxS-0001Ck-7y for qemu-devel@archiver.kernel.org; Tue, 25 Jan 2022 19:14:42 -0500 Received: from eggs.gnu.org ([209.51.188.92]:37040) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nCVex-0003T0-6N for qemu-devel@nongnu.org; Tue, 25 Jan 2022 18:55:35 -0500 Received: from mga07.intel.com ([134.134.136.100]:50816) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1nCVet-0004AJ-4n for qemu-devel@nongnu.org; Tue, 25 Jan 2022 18:55:34 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1643154931; x=1674690931; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=4TSE6Zm6S6tEQ74B0UfqdCJcrocrR2hMUptoML8fanw=; b=JbsNEe9IKc0lqz7irU0aXMJ5ewp+hAckAZNxADqavoZy+8BKoqMIr800 vv7vktDKZbx5bx1eThoyLQuLHBz2iKqvgBmJ++CAUNFR3odqW7o3D+9ij WxDkpAIMLKSAc+d61l90B8X2/D0VN+b51jz4u4WYoyg/Fge1RUk1PIZAR LoDGV327G71w7BnegKmWcXlLaEcftopZ2aaJ0NN2vZ3nHhNAa4nNkHWNp NrBLS88REnTPeXTi8vLUP5UNeYdUcnVkccBoK/5wRuqYG8FgARAYnO10p PF3d66Q61OqQP9tCc5/m80lSuRIO/H5LzseabyE4yrZLc6imlAQ1Y8lkn g==; X-IronPort-AV: E=McAfee;i="6200,9189,10238"; a="309759128" X-IronPort-AV: E=Sophos;i="5.88,316,1635231600"; d="scan'208";a="309759128" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga105.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Jan 2022 15:55:06 -0800 X-IronPort-AV: E=Sophos;i="5.88,316,1635231600"; d="scan'208";a="563229916" Received: from jungjunk-mobl1.amr.corp.intel.com (HELO intel.com) ([10.252.128.93]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Jan 2022 15:55:05 -0800 Date: Tue, 25 Jan 2022 15:55:03 -0800 From: Ben Widawsky To: Jonathan Cameron Subject: Re: [PATCH v4 00/42] CXl 2.0 emulation Support Message-ID: <20220125235503.crqfbyjtpikj3cjn@intel.com> References: <20220124171705.10432-1-Jonathan.Cameron@huawei.com> <20220125191806.ifbv2fuj2bik44zw@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220125191806.ifbv2fuj2bik44zw@intel.com> Received-SPF: pass client-ip=134.134.136.100; envelope-from=ben.widawsky@intel.com; helo=mga07.intel.com X-Spam_score_int: -45 X-Spam_score: -4.6 X-Spam_bar: ---- X-Spam_report: (-4.6 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.158, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , "Michael S . Tsirkin" , Samarth Saxena , Chris Browy , qemu-devel@nongnu.org, linux-cxl@vger.kernel.org, linuxarm@huawei.com, Shreyas Shah , Saransh Gupta1 , Shameerali Kolothum Thodi , Marcel Apfelbaum , Igor Mammedov , Dan Williams , Alex =?utf-8?Q?Benn=C3=A9e?= , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 22-01-25 11:18:08, Ben Widawsky wrote: > Really awesome work Jonathan. Dan and I are wrapping up some of the kernel bits, > so all I'll do for now is try to run this, but I hope to be able to review the > parts I'm familiar with at least. > > On 22-01-24 17:16:23, Jonathan Cameron wrote: > > Previous version was RFC v3: CXL 2.0 Support. > > No longer an RFC as I would consider the vast majority of this > > to be ready for detailed review. There are still questions called > > out in some patches however. > > > > Looking in particular for: > > * Review of the PCI interactions > > * x86 and ARM machine interactions (particularly the memory maps) > > * Review of the interleaving approach - is the basic idea > > acceptable? > > * Review of the command line interface. > > * CXL related review welcome but much of that got reviewed > > in earlier versions and hasn't changed substantially. > > > > Main changes: > > * The CXL fixed memory windows are now instantiated via a > > -cxl-fixed-memory-window command line option. As they are host level > > entities, not associated with a particular hardware entity a top > > level parameter seems the most natural way to describe them. > > This is also much closer to how it works on a real host than the > > previous assignment of a physical address window to all components > > along the CXL path. > > Excellent. > > > * Dynamic host memory physical address space allocation both for > > the CXL host bridge MMIO space and the CFMWS windows. > > I thought I had done the host bridge MMIO, but perhaps I was mistaken. Either > way, this is an important step to support all platforms more generally. > > > * Interleaving support (based loosely on Philippe Mathieu-Daudé's > > earlier work on an interleaved memory device). Note this is rudimentary > > and low performance but it may be sufficient for test purposes. > > I'll have to look at this further. I had some thoughts about how we might make > this fast, but it would be more of fake interleaving. How low is "low"? > > > * Additional PCI and memory related utility functions needed for the > > interleaving. > > * Various minor cleanup and increase in scope of tests. > > * For now dropped the support for presenting CXL type 3 devices > > as memory devices in various QEMU interfaces. > > What are the downsides to this? I only used the memory interface originally > because it seemed like a natural fit, but looking back I'm not sure we gain > much (though my memory is very lossy). > > > * Dropped the patch letting UID be different from bus_nr. Whilst > > it may be a useful thing to have, we don't need it for this series > > and so should be handled separately. > > > > I've called out patches with major changes by marking them as > > co-developed or introducing them as new patches. The original > > memory window code has been dropped > > > > After discussions at plumbers and more recently on the mailing list > > it was clear that there was interest in getting emulation for CXL 2.0 > > upstream in QEMU. This version resolves many of the outstanding issues > > and enables the following features: > > > > * Support on both x86/pc and ARM/virt with relevant ACPI tables > > generated in QEMU. > > * Host bridge based on the existing PCI Expander Bridge PXB. > > * CXL fixed memory windows, allowing host to describe interleaving > > across multiple CXL host bridges. > > * pxb-cxl CXL host bridge support including MMIO region for control > > and HDM (Host manage device memory - basically interleaving / routing) > > decoder configuration. > > * Basic CXL Root port support. > > * CXL Type 3 device support with persistent memory regions (backed by > > hostmem backend). > > * Pulled MAINTAINERS entry out to a separate patch and add myself as > > a co-maintainer at Ben's suggestion. > > > > Big TODOs: > > > > * Volatile memory devices (easy but it's more code so left for now). > > * Switch support. > > * Hotplug? May not need much but it's not tested yet! > > * More tests and tighter verification that values written to hardware > > are actually valid - stuff that real hardware would check. > > * Main host bridge support (not a priority for me...) > > I originally cared about this for the sake of making a system more realistic. I > now believe we should drop this entirely. > > > * Testing, testing and more testing. I have been running a basic > > set of ARM and x86 tests on this, but there is always room for > > more tests and greater automation. > > > > Why do we want QEMU emulation of CXL? > > > > As Ben stated in V3, QEMU support has been critical to getting OS > > software written given lack of availability of hardware supporting the > > latest CXL features (coupled with very high demand for support being > > ready in a timely fashion). What has become clear since Ben's v3 > > is that situation is a continuous one. Whilst we can't talk about > > them yet, CXL 3.0 features and OS support have been prototyped on > > top of this support and a lot of the ongoing kernel work is being > > tested against these patches. > > > > Other features on the qemu-list that build on these include PCI-DOE > > /CDAT support from the Avery Design team further showing how this > > code is useful. Whilst not directly related this is also the test > > platform for work on PCI IDE/CMA + related DMTF SPDM as CXL both > > utilizes and extends those technologies and is likely to be an early > > adopter. > > Refs: > > CMA Kernel: https://lore.kernel.org/all/20210804161839.3492053-1-Jonathan.Cameron@huawei.com/ > > CMA Qemu: https://lore.kernel.org/qemu-devel/1624665723-5169-1-git-send-email-cbrowy@avery-design.com/ > > DOE Qemu: https://lore.kernel.org/qemu-devel/1623329999-15662-1-git-send-email-cbrowy@avery-design.com/ > > > > > > As can be seen there is non trivial interaction with other areas of > > Qemu, particularly PCI and keeping this set up to date is proving > > a burden we'd rather do without :) > > > > Ben mentioned a few other good reasons in v3: > > https://lore.kernel.org/qemu-devel/20210202005948.241655-1-ben.widawsky@intel.com/ > > > > The evolution of this series perhaps leave it in a less than > > entirely obvious order and that may get tidied up in future postings. > > I'm also open to this being considered in bite sized chunks. What > > we have here is about what you need for it to be useful for testing > > currently kernel code. > > > > All comments welcome. > > > > Ben - I lifted one patch from your git tree that didn't have a > > Sign-off. hw/cxl/component Add a dumb HDM decoder handler > > Could you confirm you are happy for one to be added? > > Sure. > > > > > Example of new command line (with virt ITS patches ;) > > > > qemu-system-aarch64 -M virt,gic-version=3,cxl=on \ > > -m 4g,maxmem=8G,slots=8 \ > > ... > > -object memory-backend-file,id=cxl-mem1,share=on,mem-path=/tmp/cxltest.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-mem2,share=on,mem-path=/tmp/cxltest2.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-mem3,share=on,mem-path=/tmp/cxltest3.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-mem4,share=on,mem-path=/tmp/cxltest4.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-lsa1,share=on,mem-path=/tmp/lsa.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-lsa2,share=on,mem-path=/tmp/lsa2.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-lsa3,share=on,mem-path=/tmp/lsa3.raw,size=256M,align=256M \ > > -object memory-backend-file,id=cxl-lsa4,share=on,mem-path=/tmp/lsa4.raw,size=256M,align=256M \ > > Is align actually necessary here? > > > -object memory-backend-file,id=tt,share=on,mem-path=/tmp/tt.raw,size=1g \ > > Did you mean to put this in there? Is it somehow used internally? > > > -device pxb-cxl,bus_nr=12,bus=pcie.0,id=cxl.1 \ > > -device pxb-cxl,bus_nr=222,bus=pcie.0,id=cxl.2 \ > > -device cxl-rp,port=0,bus=cxl.1,id=root_port13,chassis=0,slot=2 \ > > -device cxl-type3,bus=root_port13,memdev=cxl-mem1,lsa=cxl-lsa1,id=cxl-pmem0,size=256M \ > > -device cxl-rp,port=1,bus=cxl.1,id=root_port14,chassis=0,slot=3 \ > > -device cxl-type3,bus=root_port14,memdev=cxl-mem2,lsa=cxl-lsa2,id=cxl-pmem1,size=256M \ > > -device cxl-rp,port=0,bus=cxl.2,id=root_port15,chassis=0,slot=5 \ > > -device cxl-type3,bus=root_port15,memdev=cxl-mem3,lsa=cxl-lsa3,id=cxl-pmem2,size=256M \ > > -device cxl-rp,port=1,bus=cxl.2,id=root_port16,chassis=0,slot=6 \ > > -device cxl-type3,bus=root_port16,memdev=cxl-mem4,lsa=cxl-lsa4,id=cxl-pmem3,size=256M \ > > -cxl-fixed-memory-window targets=cxl.1,size=4G,interleave-granularity=8k \ > > -cxl-fixed-memory-window targets=cxl.1,targets=cxl.2,size=4G,interleave-granularity=8k > > I assume interleave-ways is based on the number of targets. For testing purposes > it might be nice to add the flags as well (perhaps it's there). > This requires cxl=on machine arg now btw. > > > > First CFMWS suitable for 2 way interleave, the second for 4 way (2 way > > at host level and 2 way at the host bridge). > > targets= , multiple entries if range is disjoint. > > > > With Ben's CXL region patches (v3 shortly) plus fixes as discussed on list, > > Linux commands to bring up a 4 way interleave is: > > > > cd /sys/bus/cxl/devices/ > > region=$(cat decoder0.1/create_region) > > echo $region > decoder0.1/create_region > > ls -lh > > > > //Note the order of devices and adjust the following to make sure they > > //are in order across the 4 root ports. Easy to do in a tool, but > > //not easy to paste in a cover letter. > > > > cd region0.1\:0 > > echo 4 > interleave_ways > > echo mem2 > target0 > > echo mem3 > target1 > > echo mem0 > target2 > > echo mem1 > target3 > > echo $((1024<<20)) > size > > echo 4096 > interleave_granularity > > echo region0.1:0 > /sys/bus/cxl/drivers/cxl_region/bind > > > > Tested with devmem2 and files with known content. > > Kernel tree was based on previous version of the region patches > > from Ben with various fixes. As Dan just posted an updated version > > next job on my list is to test that. > > > > Thanks to Shameer for his help with reviewing the new stuff before > > posting. > > > > I'll post a git tree shortly for any who prefer that to lots > > of emails ;) > > > > Thanks, > > > > Jonathan > > Thanks again! > Ben > > [snip] > >