[helgaas at kernel.org: Re: aarch64 efi boot failures with qemu 6.0+]
Bjorn Helgaas
helgaas at kernel.org
Mon Jul 26 14:43:45 PDT 2021
Just FYI.
Guenter tripped over a problem with an I/O BAR set to zero. I think
your arches allow that (at least they "#define PCIBIOS_MIN_IO 0"), and
some drivers don't handle such BARs. More details below.
Note that I didn't actually cc you on the thread, mostly because I
forgot but partly to avoid exploding the cc list with people who
probably don't care. If you want to respond directly to the thread,
you can use this:
https://lore.kernel.org/qemu-devel/20210724185234.GA2265457@roeck-us.net/
----- Forwarded message from Bjorn Helgaas <helgaas at kernel.org> -----
Date: Mon, 26 Jul 2021 16:16:29 -0500
From: Bjorn Helgaas <helgaas at kernel.org>
To: Ard Biesheuvel <ardb at kernel.org>
Cc: Philippe Mathieu-Daudé <philmd at redhat.com>, Bjorn Helgaas
<bhelgaas at google.com>, Jiahui Cen <cenjiahui at huawei.com>, "Michael S.
Tsirkin" <mst at redhat.com>, Ard Biesheuvel <ardb+tianocore at kernel.org>,
qemu-devel at nongnu.org, Igor Mammedov <imammedo at redhat.com>, Guenter
Roeck <linux at roeck-us.net>
Subject: Re: aarch64 efi boot failures with qemu 6.0+
Message-ID: <20210726211628.GA640636 at bjorn-Precision-5520>
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 at 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.
I guess this is the "#define PCIBIOS_MIN_IO 0x1000" in
arm64/include/asm/pci.h. From a PCI point of view, I'm not opposed to
changing that to 0, as it is on csky, riscv, sh, sparc, um. But it's
really an arch question, so the arm64 folks would have to weigh in.
But I don't think that would fix this. PCIBIOS_MIN_IO is mainly used
when we assign or reassign resources to a BAR, and if firmware tells
us to preserve the assignments done by firmware, Linux shouldn't be
doing any assignment or reassignment.
Linux received 00:01.0 BAR 0 as [io 0x0000-0x007f], and Guenter didn't
report any reassignment, so I assume Linux saw the
DSM_PCI_PRESERVE_BOOT_CONFIG [1] and didn't change anything.
Could this be due to drivers assuming that an I/O BAR of 0 is invalid?
I see that at least ne2k_pci_init_one() [2] seems to assume that. And
tulip_init_one() [3] and pci_esp_probe_one() (am53c974.c, [4]) use
pci_iomap() [5], which fails if the resource starts at 0.
So pci_iomap() is probably already broken on the arches above that
allow I/O BARs to be zero. Maybe pci_iomap() should only fail on
"!start" for *memory* BARs, e.g.,
diff --git a/lib/pci_iomap.c b/lib/pci_iomap.c
index 2d3eb1cb73b8..77455e702a3e 100644
--- a/lib/pci_iomap.c
+++ b/lib/pci_iomap.c
@@ -34,7 +34,9 @@ void __iomem *pci_iomap_range(struct pci_dev *dev,
resource_size_t len = pci_resource_len(dev, bar);
unsigned long flags = pci_resource_flags(dev, bar);
- if (len <= offset || !start)
+ if (flags & IORESOURCE_MEM && !start)
+ return NULL;
+ if (len <= offset)
return NULL;
len -= offset;
start += offset;
[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/acpi/pci_root.c?id=v5.13#n915
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/8390/ne2k-pci.c?id=v5.13#n247
[3] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/ethernet/dec/tulip/tulip_core.c?id=v5.13#n1418
[4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/scsi/am53c974.c?id=v5.13#n431
[5] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/lib/pci_iomap.c?id=v5.13#n37
> > >>> and the controller does not instantiate. The problem disapears after
> > >>> reverting commit 0cf8882fd0.
> > >>>
> > >>> Attached is a summary of test runs with various devices and qemu v5.2
> > >>> as well as qemu v6.0, and the command line I use for efi boots.
> > >>>
> > >>> Did commit 0cf8882fd0 introduce a bug, do I now need need some different
> > >>> command line to instantiate PCI devices with io ports, or are such
> > >>> devices
> > >>> simply no longer supported if the system is booted with efi support ?
> > >>>
> > >>> Thanks,
> > >>> Guenter
> > >>
> > >>
> > >> So that commit basically just says don't ignore what efi did.
> > >>
> > >> The issue's thus likely efi.
> > >>
> > >
> > > I don't see the problem with efi boots on x86 and x86_64.
> > > Any idea why that might be the case ?
> > >
> > > Thanks,
> > > Guenter
> > >
> > >> Cc the maintainer. Philippe can you comment pls?
> >
> > I'll have a look. Cc'ing Ard for EDK2/Aarch64.
>
> So a potential workaround would be to use a different I/O resource
> window for ArmVirtPkg, that starts at 0x1000. But I would prefer to
> fix Linux instead.
>
>
> > >>
> > >>> ---
> > >>> Command line (tulip network interface):
> > >>>
> > >>> CMDLINE="root=/dev/vda console=ttyAMA0"
> > >>> ROOTFS="rootfs.ext2"
> > >>>
> > >>> qemu-system-aarch64 -M virt -kernel arch/arm64/boot/Image -no-reboot \
> > >>> -m 512 -cpu cortex-a57 -no-reboot \
> > >>> -device tulip,netdev=net0 -netdev user,id=net0 \
> > >>> -bios QEMU_EFI-aarch64.fd \
> > >>> -snapshot \
> > >>> -device virtio-blk-device,drive=d0 \
> > >>> -drive file=${ROOTFS},if=none,id=d0,format=raw \
> > >>> -nographic -serial stdio -monitor none \
> > >>> --append "${CMDLINE}"
> > >>>
> > >>> ---
> > >>> Boot tests with various devices known to work in qemu v5.2.
> > >>>
> > >>> v5.2 v6.0 v6.0
> > >>> efi non-efi efi
> > >>> e1000 pass pass pass
> > >>> e1000-82544gc pass pass pass
> > >>> e1000-82545em pass pass pass
> > >>> e1000e pass pass pass
> > >>> i82550 pass pass pass
> > >>> i82557a pass pass pass
> > >>> i82557b pass pass pass
> > >>> i82557c pass pass pass
> > >>> i82558a pass pass pass
> > >>> i82559b pass pass pass
> > >>> i82559c pass pass pass
> > >>> i82559er pass pass pass
> > >>> i82562 pass pass pass
> > >>> i82801 pass pass pass
> > >>> ne2k_pci pass pass fail <--
> > >>> pcnet pass pass pass
> > >>> rtl8139 pass pass pass
> > >>> tulip pass pass fail <--
> > >>> usb-net pass pass pass
> > >>> virtio-net-device
> > >>> pass pass pass
> > >>> virtio-net-pci pass pass pass
> > >>> virtio-net-pci-non-transitional
> > >>> pass pass pass
> > >>>
> > >>> usb-xhci pass pass pass
> > >>> usb-ehci pass pass pass
> > >>> usb-ohci pass pass pass
> > >>> usb-uas-xhci pass pass pass
> > >>> virtio pass pass pass
> > >>> virtio-blk-pci pass pass pass
> > >>> virtio-blk-device
> > >>> pass pass pass
> > >>> nvme pass pass pass
> > >>> sdhci pass pass pass
> > >>> dc390 pass pass fail <--
> > >>> am53c974 pass pass fail <--
> > >>> lsi53c895ai pass pass pass
> > >>> mptsas1068 pass pass pass
> > >>> lsi53c810 pass pass pass
> > >>> megasas pass pass pass
> > >>> megasas-gen2 pass pass pass
> > >>> virtio-scsi-device
> > >>> pass pass pass
> > >>> virtio-scsi-pci pass pass pass
> > >>
> > >
> >
>
----- End forwarded message -----
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