# git rev-parse -q --verify bddac7c1e02ba47f0570e494c9289acea3062cc1^{commit}
bddac7c1e02ba47f0570e494c9289acea3062cc1
already have revision, skipping fetch
# git checkout -q -f -B kisskb bddac7c1e02ba47f0570e494c9289acea3062cc1
# git clean -qxdf
# < git log -1
# commit bddac7c1e02ba47f0570e494c9289acea3062cc1
# Author: Linus Torvalds <torvalds@linux-foundation.org>
# Date:   Sat Mar 26 10:42:04 2022 -0700
# 
#     Revert "swiotlb: rework "fix info leak with DMA_FROM_DEVICE""
#     
#     This reverts commit aa6f8dcbab473f3a3c7454b74caa46d36cdc5d13.
#     
#     It turns out this breaks at least the ath9k wireless driver, and
#     possibly others.
#     
#     What the ath9k driver does on packet receive is to set up the DMA
#     transfer with:
#     
#       int ath_rx_init(..)
#       ..
#                     bf->bf_buf_addr = dma_map_single(sc->dev, skb->data,
#                                                      common->rx_bufsize,
#                                                      DMA_FROM_DEVICE);
#     
#     and then the receive logic (through ath_rx_tasklet()) will fetch
#     incoming packets
#     
#       static bool ath_edma_get_buffers(..)
#       ..
#             dma_sync_single_for_cpu(sc->dev, bf->bf_buf_addr,
#                                     common->rx_bufsize, DMA_FROM_DEVICE);
#     
#             ret = ath9k_hw_process_rxdesc_edma(ah, rs, skb->data);
#             if (ret == -EINPROGRESS) {
#                     /*let device gain the buffer again*/
#                     dma_sync_single_for_device(sc->dev, bf->bf_buf_addr,
#                                     common->rx_bufsize, DMA_FROM_DEVICE);
#                     return false;
#             }
#     
#     and it's worth noting how that first DMA sync:
#     
#         dma_sync_single_for_cpu(..DMA_FROM_DEVICE);
#     
#     is there to make sure the CPU can read the DMA buffer (possibly by
#     copying it from the bounce buffer area, or by doing some cache flush).
#     The iommu correctly turns that into a "copy from bounce bufer" so that
#     the driver can look at the state of the packets.
#     
#     In the meantime, the device may continue to write to the DMA buffer, but
#     we at least have a snapshot of the state due to that first DMA sync.
#     
#     But that _second_ DMA sync:
#     
#         dma_sync_single_for_device(..DMA_FROM_DEVICE);
#     
#     is telling the DMA mapping that the CPU wasn't interested in the area
#     because the packet wasn't there.  In the case of a DMA bounce buffer,
#     that is a no-op.
#     
#     Note how it's not a sync for the CPU (the "for_device()" part), and it's
#     not a sync for data written by the CPU (the "DMA_FROM_DEVICE" part).
#     
#     Or rather, it _should_ be a no-op.  That's what commit aa6f8dcbab47
#     broke: it made the code bounce the buffer unconditionally, and changed
#     the DMA_FROM_DEVICE to just unconditionally and illogically be
#     DMA_TO_DEVICE.
#     
#     [ Side note: purely within the confines of the swiotlb driver it wasn't
#       entirely illogical: The reason it did that odd DMA_FROM_DEVICE ->
#       DMA_TO_DEVICE conversion thing is because inside the swiotlb driver,
#       it uses just a swiotlb_bounce() helper that doesn't care about the
#       whole distinction of who the sync is for - only which direction to
#       bounce.
#     
#       So it took the "sync for device" to mean that the CPU must have been
#       the one writing, and thought it meant DMA_TO_DEVICE. ]
#     
#     Also note how the commentary in that commit was wrong, probably due to
#     that whole confusion, claiming that the commit makes the swiotlb code
#     
#                                       "bounce unconditionally (that is, also
#         when dir == DMA_TO_DEVICE) in order do avoid synchronising back stale
#         data from the swiotlb buffer"
#     
#     which is nonsensical for two reasons:
#     
#      - that "also when dir == DMA_TO_DEVICE" is nonsensical, as that was
#        exactly when it always did - and should do - the bounce.
#     
#      - since this is a sync for the device (not for the CPU), we're clearly
#        fundamentally not coping back stale data from the bounce buffers at
#        all, because we'd be copying *to* the bounce buffers.
#     
#     So that commit was just very confused.  It confused the direction of the
#     synchronization (to the device, not the cpu) with the direction of the
#     DMA (from the device).
#     
#     Reported-and-bisected-by: Oleksandr Natalenko <oleksandr@natalenko.name>
#     Reported-by: Olha Cherevyk <olha.cherevyk@gmail.com>
#     Cc: Halil Pasic <pasic@linux.ibm.com>
#     Cc: Christoph Hellwig <hch@lst.de>
#     Cc: Kalle Valo <kvalo@kernel.org>
#     Cc: Robin Murphy <robin.murphy@arm.com>
#     Cc: Toke Høiland-Jørgensen <toke@toke.dk>
#     Cc: Maxime Bizon <mbizon@freebox.fr>
#     Cc: Johannes Berg <johannes@sipsolutions.net>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/korg/gcc-11.1.0-nolibc/xtensa-linux/bin/xtensa-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-11.1.0-nolibc/xtensa-linux/bin/xtensa-linux-ld --version
# < git log --format=%s --max-count=1 bddac7c1e02ba47f0570e494c9289acea3062cc1
# < make -s -j 120 ARCH=xtensa O=/kisskb/build/linus_xtensa-allmodconfig_xtensa-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.1.0-nolibc/xtensa-linux/bin/xtensa-linux-  allmodconfig
# Added to kconfig CONFIG_BUILD_DOCSRC=n
# Added to kconfig CONFIG_MODULE_SIG=n
# Added to kconfig CONFIG_SAMPLES=n
# < make -s -j 120 ARCH=xtensa O=/kisskb/build/linus_xtensa-allmodconfig_xtensa-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.1.0-nolibc/xtensa-linux/bin/xtensa-linux-  help
# make -s -j 120 ARCH=xtensa O=/kisskb/build/linus_xtensa-allmodconfig_xtensa-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.1.0-nolibc/xtensa-linux/bin/xtensa-linux-  olddefconfig
# make -s -j 120 ARCH=xtensa O=/kisskb/build/linus_xtensa-allmodconfig_xtensa-gcc11 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-11.1.0-nolibc/xtensa-linux/bin/xtensa-linux-  
WARNING: modpost: vmlinux.o(.text.unlikely+0x45d8): Section mismatch in reference from the function __trace_event_discard_commit() to the variable .init.data:initcall_level_names
The function __trace_event_discard_commit() references
the variable __initdata initcall_level_names.
This is often because __trace_event_discard_commit lacks a __initdata 
annotation or the annotation of initcall_level_names is wrong.

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14410): Section mismatch in reference from the variable qed_mfw_legacy_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_legacy_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14428): Section mismatch in reference from the variable qed_mfw_legacy_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_legacy_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14440): Section mismatch in reference from the variable qed_mfw_legacy_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_legacy_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14458): Section mismatch in reference from the variable qed_mfw_legacy_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_legacy_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14470): Section mismatch in reference from the variable qed_mfw_legacy_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_legacy_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14488): Section mismatch in reference from the variable qed_mfw_legacy_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_legacy_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x144a0): Section mismatch in reference from the variable qed_mfw_legacy_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_legacy_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x144f0): Section mismatch in reference from the variable qed_mfw_ext_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_ext_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14508): Section mismatch in reference from the variable qed_mfw_ext_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_ext_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14520): Section mismatch in reference from the variable qed_mfw_ext_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_ext_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14538): Section mismatch in reference from the variable qed_mfw_ext_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_ext_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14550): Section mismatch in reference from the variable qed_mfw_ext_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_ext_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14568): Section mismatch in reference from the variable qed_mfw_ext_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_ext_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14580): Section mismatch in reference from the variable qed_mfw_ext_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_ext_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qed/qed.o(.data+0x14598): Section mismatch in reference from the variable qed_mfw_ext_maps to the variable .init.rodata:qed_mfw_legacy_bb_100g
The variable qed_mfw_ext_maps references
the variable __initconst qed_mfw_legacy_bb_100g
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qede/qede.o(.data+0x4790): Section mismatch in reference from the variable qede_forced_speed_maps to the variable .init.rodata:qede_forced_speed_100000
The variable qede_forced_speed_maps references
the variable __initconst qede_forced_speed_100000
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qede/qede.o(.data+0x47a8): Section mismatch in reference from the variable qede_forced_speed_maps to the variable .init.rodata:qede_forced_speed_100000
The variable qede_forced_speed_maps references
the variable __initconst qede_forced_speed_100000
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qede/qede.o(.data+0x47c0): Section mismatch in reference from the variable qede_forced_speed_maps to the variable .init.rodata:qede_forced_speed_100000
The variable qede_forced_speed_maps references
the variable __initconst qede_forced_speed_100000
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qede/qede.o(.data+0x47d8): Section mismatch in reference from the variable qede_forced_speed_maps to the variable .init.rodata:qede_forced_speed_100000
The variable qede_forced_speed_maps references
the variable __initconst qede_forced_speed_100000
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qede/qede.o(.data+0x47f0): Section mismatch in reference from the variable qede_forced_speed_maps to the variable .init.rodata:qede_forced_speed_100000
The variable qede_forced_speed_maps references
the variable __initconst qede_forced_speed_100000
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qede/qede.o(.data+0x4808): Section mismatch in reference from the variable qede_forced_speed_maps to the variable .init.rodata:qede_forced_speed_100000
The variable qede_forced_speed_maps references
the variable __initconst qede_forced_speed_100000
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

WARNING: modpost: drivers/net/ethernet/qlogic/qede/qede.o(.data+0x4820): Section mismatch in reference from the variable qede_forced_speed_maps to the variable .init.rodata:qede_forced_speed_100000
The variable qede_forced_speed_maps references
the variable __initconst qede_forced_speed_100000
If the reference is valid then annotate the
variable with __init* or __refdata (see linux/init.h) or name the variable:
*_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

Completed OK
# rm -rf /kisskb/build/linus_xtensa-allmodconfig_xtensa-gcc11
# Build took: 0:06:45.659500