Re: [PATCH 5/6] hw/mips/gt64xxx_pci: Endian-swap using PCI_HOST_BRIDGE MemoryRegionOps

[Nathan Chancellor]

Hi Philippe,

On Wed, Jan 04, 2023 at 02:39:34PM +0100, Philippe Mathieu-Daudé wrote:
> GT64120's PCI endianness swapping works on little-endian hosts,
> but doesn't on big-endian ones. Instead of complicating how
> CFGADDR/CFGDATA registers deal with endianness, use the existing
> MemoryRegionOps from hw/pci/pci_host.c. Doing so also reduce the
> access to internal PCI_HOST_BRIDGE fields.
> 
> Map the PCI_HOST_BRIDGE MemoryRegionOps into the corresponding
> CFGADDR/CFGDATA regions in the ISD MMIO and remove the unused
> code in the current ISD read/write handlers.
> 
> Update the mapping when PCI0_CMD register is accessed (in case
> the endianness is changed).
> 
> This allows using the GT64120 on a big-endian host (and boot
> the MIPS Malta machine in little-endian).
> 
> Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

This change as commit 145e2198d7 ("hw/mips/gt64xxx_pci: Endian-swap
using PCI_HOST_BRIDGE MemoryRegionOps") in QEMU master causes a hang
when trying to poweroff a malta_defconfig + CONFIG_CPU_BIG_ENDIAN=y
kernel on an x86_64 host. The kernel has been built from latest mainline
using the kernel.org toolchains [1], just in case it matters.

$ timeout --foreground 30s qemu-system-mips \
-cpu 24Kf \
-machine malta \
-kernel vmlinux \
-display none \
-initrd rootfs.cpio \
-m 512m \
-nodefaults \
-no-reboot \
-serial mon:stdio
...
Run /init as init process
process '/bin/busybox' started with executable stack
Starting syslogd: OK
Starting klogd: OK
Running sysctl: OK
Saving random seed: OK
Starting network: OK
Linux version 6.2.0-rc5-00013-g2475bf0250de (tuxmake@tuxmake) (mips-linux-gcc 
(GCC) 12.2.0, GNU ld (GNU Binutils) 2.39) #1 SMP @1674418498
Stopping network: OK
Saving random seed: OK
Stopping klogd: OK
Stopping syslogd: OK
umount: devtmpfs busy - remounted read-only
umount: can't unmount /: Invalid argument
The system is going down NOW!
Sent SIGTERM to all processes
Sent SIGKILL to all processes
Requesting system poweroff
reboot: System halted
qemu-system-mips: terminating on signal 15 from pid 2213875 (timeout)

The rootfs is available at [2], if it is necessary. It is a simple
buildroot initramfs that just prints the version string and shutsdown
the machine

If there is any additional information that I can provide or patches I
can test, please let me know.

[1]: https://mirrors.edge.kernel.org/pub/tools/crosstool/
[2]: 
https://github.com/ClangBuiltLinux/boot-utils/tree/1b837f3b0fca441e0cc694c9b587120e81299554/images/mips

Cheers,
Nathan

# bad: [00b1faea41d283e931256aa78aa975a369ec3ae6] Merge tag 
'pull-target-arm-20230123' of https://git.linaro.org/people/pmaydell/qemu-arm 
into staging
# good: [886fb67020e32ce6a2cf7049c6f017acf1f0d69a] Merge tag 
'pull-target-arm-20230113' of https://git.linaro.org/people/pmaydell/qemu-arm 
into staging
git bisect start '00b1faea41d283e931256aa78aa975a369ec3ae6' 
'886fb67020e32ce6a2cf7049c6f017acf1f0d69a'
# bad: [239b8b0699a222fd21da1c5fdeba0a2456085a47] Merge tag 
'trivial-branch-for-8.0-pull-request' of https://gitlab.com/laurent_vivier/qemu 
into staging
git bisect bad 239b8b0699a222fd21da1c5fdeba0a2456085a47
# bad: [a48f692929828212f75eb6e8d11bbb6cdffad153] hw/usb: Mark the 
XLNX_VERSAL-related files as target-independent
git bisect bad a48f692929828212f75eb6e8d11bbb6cdffad153
# bad: [a844873512400fae6bed9e87694dc96ff2f15f39] mips: Remove support for trap 
and emulate KVM
git bisect bad a844873512400fae6bed9e87694dc96ff2f15f39
# bad: [cd5066f8618bc6c80ec9088923c58f4a42ab0e7a] hw/mips/bootloader: Handle 
buffers as opaque arrays
git bisect bad cd5066f8618bc6c80ec9088923c58f4a42ab0e7a
# bad: [37e506b69a6791bede30677f05081296f3b77f77] hw/mips/gt64xxx_pci: Let the 
GT64120 manage the lower 512MiB hole
git bisect bad 37e506b69a6791bede30677f05081296f3b77f77
# good: [65423e6efeac1ee1057870361337c572c941140c] hw/mips/gt64xxx_pci: 
Accumulate address space changes
git bisect good 65423e6efeac1ee1057870361337c572c941140c
# bad: [7c032bfbe838c24dcbdc8f9c452553b24f20daad] hw/mips/Kconfig: Introduce 
CONFIG_GT64120 to select gt64xxx_pci.c
git bisect bad 7c032bfbe838c24dcbdc8f9c452553b24f20daad
# bad: [145e2198d749ec09a405f1607a9932499b76f1eb] hw/mips/gt64xxx_pci: 
Endian-swap using PCI_HOST_BRIDGE MemoryRegionOps
git bisect bad 145e2198d749ec09a405f1607a9932499b76f1eb
# first bad commit: [145e2198d749ec09a405f1607a9932499b76f1eb] 
hw/mips/gt64xxx_pci: Endian-swap using PCI_HOST_BRIDGE MemoryRegionOps