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

["Alex Bennée" <alex.bennee@linaro.org>]

Nathan Chancellor <nathan@kernel.org> writes:

> 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
> ...
<snip>

Ahh also this commit got fingered by the tuxrun test for the same
combination:

  ./run --runtime docker --qemu-binary /home/alex.bennee/lsrc/qemu.git/builds/bisect/qemu-system-mips64 --device qemu-mips64

with my in flight patches for tuxrun's host support.

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro