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Tsirkin" , Ard Biesheuvel References: <20210724185234.GA2265457@roeck-us.net> <20210725181334-mutt-send-email-mst@kernel.org> <14aff6ab-0b96-fe22-bc35-18d2e8528a5b@roeck-us.net> <2a4076fd-2225-b3a8-7a1e-3bc090046673@redhat.com> <20210727004401-mutt-send-email-mst@kernel.org> <20210727052516-mutt-send-email-mst@kernel.org> From: Guenter Roeck Message-ID: Date: Tue, 27 Jul 2021 04:18:30 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210727052516-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2607:f8b0:4864:20::730; envelope-from=groeck7@gmail.com; helo=mail-qk1-x730.google.com X-Spam_score_int: -16 X-Spam_score: -1.7 X-Spam_bar: - X-Spam_report: (-1.7 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_ENVFROM_END_DIGIT=0.25, FREEMAIL_FORGED_FROMDOMAIN=0.25, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.25, NICE_REPLY_A=-0.438, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jiahui Cen , Ard Biesheuvel , qemu-devel@nongnu.org, Bjorn Helgaas , Igor Mammedov , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 7/27/21 2:30 AM, Michael S. Tsirkin wrote: > On Tue, Jul 27, 2021 at 09:04:20AM +0200, Ard Biesheuvel wrote: >> On Tue, 27 Jul 2021 at 07:12, Guenter Roeck wrote: >>> >>> On 7/26/21 9:45 PM, Michael S. Tsirkin wrote: >>>> On Mon, Jul 26, 2021 at 06:00:57PM +0200, Ard Biesheuvel wrote: >>>>> (cc Bjorn) >>>>> >>>>> On Mon, 26 Jul 2021 at 11:08, Philippe Mathieu-Daudé wrote: >>>>>> >>>>>> On 7/26/21 12:56 AM, Guenter Roeck wrote: >>>>>>> On 7/25/21 3:14 PM, Michael S. Tsirkin wrote: >>>>>>>> On Sat, Jul 24, 2021 at 11:52:34AM -0700, Guenter Roeck wrote: >>>>>>>>> Hi all, >>>>>>>>> >>>>>>>>> starting with qemu v6.0, some of my aarch64 efi boot tests no longer >>>>>>>>> work. Analysis shows that PCI devices with IO ports do not instantiate >>>>>>>>> in qemu v6.0 (or v6.1-rc0) when booting through efi. The problem affects >>>>>>>>> (at least) ne2k_pci, tulip, dc390, and am53c974. The problem only >>>>>>>>> affects >>>>>>>>> aarch64, not x86/x86_64. >>>>>>>>> >>>>>>>>> I bisected the problem to commit 0cf8882fd0 ("acpi/gpex: Inform os to >>>>>>>>> keep firmware resource map"). Since this commit, PCI device BAR >>>>>>>>> allocation has changed. Taking tulip as example, the kernel reports >>>>>>>>> the following PCI bar assignments when running qemu v5.2. >>>>>>>>> >>>>>>>>> [ 3.921801] pci 0000:00:01.0: [1011:0019] type 00 class 0x020000 >>>>>>>>> [ 3.922207] pci 0000:00:01.0: reg 0x10: [io 0x0000-0x007f] >>>>>>>>> [ 3.922505] pci 0000:00:01.0: reg 0x14: [mem 0x10000000-0x1000007f] >>>>> >>>>> IIUC, these lines are read back from the BARs >>>>> >>>>>>>>> [ 3.927111] pci 0000:00:01.0: BAR 0: assigned [io 0x1000-0x107f] >>>>>>>>> [ 3.927455] pci 0000:00:01.0: BAR 1: assigned [mem >>>>>>>>> 0x10000000-0x1000007f] >>>>>>>>> >>>>> >>>>> ... and this is the assignment created by the kernel. >>>>> >>>>>>>>> With qemu v6.0, the assignment is reported as follows. >>>>>>>>> >>>>>>>>> [ 3.922887] pci 0000:00:01.0: [1011:0019] type 00 class 0x020000 >>>>>>>>> [ 3.923278] pci 0000:00:01.0: reg 0x10: [io 0x0000-0x007f] >>>>>>>>> [ 3.923451] pci 0000:00:01.0: reg 0x14: [mem 0x10000000-0x1000007f] >>>>>>>>> >>>>> >>>>> The problem here is that Linux, for legacy reasons, does not support >>>>> I/O ports <= 0x1000 on PCI, so the I/O assignment created by EFI is >>>>> rejected. >>>>> >>>>> This might make sense on x86, where legacy I/O ports may exist, but on >>>>> other architectures, this makes no sense. >>>> >>>> >>>> Fixing Linux makes sense but OTOH EFI probably shouldn't create mappings >>>> that trip up existing guests, right? >>>> >>> >>> I think it is difficult to draw a line. Sure, maybe EFI should not create >>> such mappings, but then maybe qemu should not suddenly start to enforce >>> those mappings for existing guests either. >>> >> >> EFI creates the mappings primarily for itself, and up until DSM #5 >> started to be enforced, all PCI resource allocations that existed at >> boot were ignored by Linux and recreated from scratch. >> >> Also, the commit in question looks dubious to me. I don't think it is >> likely that Linux would fail to create a resource tree. What does >> happen is that BARs get moved around, which may cause trouble in some >> cases: for instance, we had to add special code to the EFI framebuffer >> driver to copy with framebuffer BARs being relocated. >> >>> For my own testing, I simply reverted commit 0cf8882fd0 in my copy of >>> qemu. That solves my immediate problem, giving us time to find a solution >>> that is acceptable for everyone. After all, it doesn't look like anyone >>> else has noticed the problem, so there is no real urgency. >>> >> >> I would argue that it is better to revert that commit. DSM #5 has a >> long history of debate and misinterpretation, and while I think we >> ended up with something sane, I don't think we should be using it in >> this particular case. > > I think revert might make sense, however: > > 0: No (The operating system shall not ignore the PCI configuration that firmware has done > at boot time. However, the operating system is free to configure the devices in this hierarchy > that have not been configured by the firmware. There may be a reduced level of hot plug > capability support in this hierarchy due to resource constraints. This situation is the same as > the legacy situation where this _DSM is not provided.) > > ^^^^ does not this imply that reporting a 0 as we currently do > should be mostly a NOP? > > > 1: Yes (The operating system may ignore the PCI configuration that the firmware has done > at boot time, and reconfigure/rebalance the resources in the hierarchy.) > > > So I am debating with myself whether this should be a plain revert or > return 1 here: > /* > * 0 - The operating system must not ignore the PCI configuration that > * firmware has done at boot time. > */ > aml_append(ifctx1, aml_return(aml_int(0))); > - aml_append(ifctx, ifctx1); > + aml_append(ifctx1, aml_return(aml_int(1))); > aml_append(method, ifctx); > > > > Guenter what happens if we return 1? Do things work well? > Yes. Guenter