Re: aarch64 efi boot failures with qemu 6.0+

[Bjorn Helgaas]

[+cc linux-pci]

On Mon, Jul 26, 2021 at 04:16:29PM -0500, Bjorn Helgaas wrote:
> On Mon, Jul 26, 2021 at 06:00:57PM +0200, Ard Biesheuvel wrote:
> > 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.
> 
> 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
> > > >>
> > > >
> > >
> >