qemu-devel.nongnu.org archive mirror
 help / color / mirror / Atom feed
From: Guenter Roeck <linux@roeck-us.net>
To: "Michael S. Tsirkin" <mst@redhat.com>, Ard Biesheuvel <ardb@kernel.org>
Cc: "Jiahui Cen" <cenjiahui@huawei.com>,
	"Ard Biesheuvel" <ardb+tianocore@kernel.org>,
	qemu-devel@nongnu.org, "Bjorn Helgaas" <bhelgaas@google.com>,
	"Igor Mammedov" <imammedo@redhat.com>,
	"Philippe Mathieu-Daudé" <philmd@redhat.com>
Subject: Re: aarch64 efi boot failures with qemu 6.0+
Date: Tue, 27 Jul 2021 04:18:30 -0700	[thread overview]
Message-ID: <b5b08783-4485-0d9c-0156-169675cf4aee@roeck-us.net> (raw)
In-Reply-To: <20210727052516-mutt-send-email-mst@kernel.org>

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 <linux@roeck-us.net> 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 <philmd@redhat.com> 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


  parent reply	other threads:[~2021-07-27 11:19 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-24 18:52 Guenter Roeck
2021-07-25 22:14 ` Michael S. Tsirkin
2021-07-25 22:56   ` Guenter Roeck
2021-07-26  9:08     ` Philippe Mathieu-Daudé
2021-07-26 16:00       ` Ard Biesheuvel
2021-07-26 21:16         ` Bjorn Helgaas
2021-07-26 21:31           ` Bjorn Helgaas
2021-07-27  4:22             ` Guenter Roeck
2021-07-27 14:25               ` Bjorn Helgaas
2021-07-27  4:45         ` Michael S. Tsirkin
2021-07-27  5:12           ` Guenter Roeck
2021-07-27  7:04             ` Ard Biesheuvel
2021-07-27  9:02               ` Michael S. Tsirkin
2021-07-27  9:30               ` Michael S. Tsirkin
2021-07-27  9:50                 ` Ard Biesheuvel
2021-07-27 10:07                   ` Michael S. Tsirkin
2021-07-27 10:14                     ` Ard Biesheuvel
2021-07-27 11:18                 ` Guenter Roeck [this message]
2021-07-27  9:01             ` Michael S. Tsirkin
2021-07-27 10:36               ` Igor Mammedov
2021-07-27 11:32                 ` Guenter Roeck
2021-07-28 13:11                 ` Michael S. Tsirkin
2021-07-28 13:25                   ` Ard Biesheuvel
2021-07-28 14:03                     ` Guenter Roeck
2021-07-29  8:08                       ` Philippe Mathieu-Daudé
2021-07-29 14:42                         ` Bjorn Helgaas
2021-07-29 15:59                           ` Michael S. Tsirkin

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=b5b08783-4485-0d9c-0156-169675cf4aee@roeck-us.net \
    --to=linux@roeck-us.net \
    --cc=ardb+tianocore@kernel.org \
    --cc=ardb@kernel.org \
    --cc=bhelgaas@google.com \
    --cc=cenjiahui@huawei.com \
    --cc=imammedo@redhat.com \
    --cc=mst@redhat.com \
    --cc=philmd@redhat.com \
    --cc=qemu-devel@nongnu.org \
    --subject='Re: aarch64 efi boot failures with qemu 6.0+' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).