# git rev-parse -q --verify 6d3350efdc57b346112536c8e413e88940233642^{commit}
6d3350efdc57b346112536c8e413e88940233642
already have revision, skipping fetch
# git checkout -q -f -B kisskb 6d3350efdc57b346112536c8e413e88940233642
# git clean -qxdf
# < git log -1
# commit 6d3350efdc57b346112536c8e413e88940233642
# Author: Michael Ellerman <mpe@ellerman.id.au>
# Date:   Tue Nov 6 23:37:58 2018 +1100
# 
#     powerpc/io: Fix the IO workarounds code to work with Radix
#     
#     Back in 2006 Ben added some workarounds for a misbehaviour in the
#     Spider IO bridge used on early Cell machines, see commit
#     014da7ff47b5 ("[POWERPC] Cell "Spider" MMIO workarounds"). Later these
#     were made to be generic, ie. not tied specifically to Spider.
#     
#     The code stashes a token in the high bits (59-48) of virtual addresses
#     used for IO (eg. returned from ioremap()). This works fine when using
#     the Hash MMU, but when we're using the Radix MMU the bits used for the
#     token overlap with some of the bits of the virtual address.
#     
#     This is because the maximum virtual address is larger with Radix, up
#     to c00fffffffffffff, and in fact we use that high part of the address
#     range for ioremap(), see RADIX_KERN_IO_START.
#     
#     As it happens the bits that are used overlap with the bits that
#     differentiate an IO address vs a linear map address. If the resulting
#     address lies outside the linear mapping we will crash (see below), if
#     not we just corrupt memory.
#     
#       virtio-pci 0000:00:00.0: Using 64-bit direct DMA at offset 800000000000000
#       Unable to handle kernel paging request for data at address 0xc000000080000014
#       ...
#       CFAR: c000000000626b98 DAR: c000000080000014 DSISR: 42000000 IRQMASK: 0
#       GPR00: c0000000006c54fc c00000003e523378 c0000000016de600 0000000000000000
#       GPR04: c00c000080000014 0000000000000007 0fffffff000affff 0000000000000030
#              ^^^^
#       ...
#       NIP [c000000000626c5c] .iowrite8+0xec/0x100
#       LR [c0000000006c992c] .vp_reset+0x2c/0x90
#       Call Trace:
#         .pci_bus_read_config_dword+0xc4/0x120 (unreliable)
#         .register_virtio_device+0x13c/0x1c0
#         .virtio_pci_probe+0x148/0x1f0
#         .local_pci_probe+0x68/0x140
#         .pci_device_probe+0x164/0x220
#         .really_probe+0x274/0x3b0
#         .driver_probe_device+0x80/0x170
#         .__driver_attach+0x14c/0x150
#         .bus_for_each_dev+0xb8/0x130
#         .driver_attach+0x34/0x50
#         .bus_add_driver+0x178/0x2f0
#         .driver_register+0x90/0x1a0
#         .__pci_register_driver+0x6c/0x90
#         .virtio_pci_driver_init+0x2c/0x40
#         .do_one_initcall+0x64/0x280
#         .kernel_init_freeable+0x36c/0x474
#         .kernel_init+0x24/0x160
#         .ret_from_kernel_thread+0x58/0x7c
#     
#     This hasn't been a problem because CONFIG_PPC_IO_WORKAROUNDS which
#     enables this code is usually not enabled. It is only enabled when it's
#     selected by PPC_CELL_NATIVE which is only selected by
#     PPC_IBM_CELL_BLADE and that in turn depends on BIG_ENDIAN. So in order
#     to hit the bug you need to build a big endian kernel, with IBM Cell
#     Blade support enabled, as well as Radix MMU support, and then boot
#     that on Power9 using Radix MMU.
#     
#     Still we can fix the bug, so let's do that. We simply use fewer bits
#     for the token, taking the union of the restrictions on the address
#     from both Hash and Radix, we end up with 8 bits we can use for the
#     token. The only user of the token is iowa_mem_find_bus() which only
#     supports 8 token values, so 8 bits is plenty for that.
#     
#     Fixes: 566ca99af026 ("powerpc/mm/radix: Add dummy radix_enabled()")
#     Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
# < /opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-gcc --version
# < git log --format=%s --max-count=1 6d3350efdc57b346112536c8e413e88940233642
# < make -s -j 120 ARCH=powerpc O=/kisskb/build/powerpc-fixes_chrp32_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  chrp32_defconfig
# make -s -j 120 ARCH=powerpc O=/kisskb/build/powerpc-fixes_chrp32_defconfig_powerpc-gcc5 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-5.5.0-nolibc/powerpc64-linux/bin/powerpc64-linux-  
Completed OK
# rm -rf /kisskb/build/powerpc-fixes_chrp32_defconfig_powerpc-gcc5
# Build took: 0:00:19.653290