linux.git/kernel/dma, branch v5.18

dma-direct: avoid redundant memory sync for swiotlb

2022-04-14T04:30:39+00:00

When we looked into FIO performance with swiotlb enabled in VM, we found
swiotlb_bounce() is always called one more time than expected for each DMA
read request.

It turns out that the bounce buffer is copied to original DMA buffer twice
after the completion of a DMA request (one is done by in
dma_direct_sync_single_for_cpu(), the other by swiotlb_tbl_unmap_single()).
But the content in bounce buffer actually doesn't change between the two
rounds of copy. So, one round of copy is redundant.

Pass DMA_ATTR_SKIP_CPU_SYNC flag to swiotlb_tbl_unmap_single() to
skip the memory copy in it.

This fix increases FIO 64KB sequential read throughput in a guest with
swiotlb=force by 5.6%.

Fixes: 55897af63091 ("dma-direct: merge swiotlb_dma_ops into the dma_direct code")
Reported-by: Wang Zhaoyang1 
Reported-by: Gao Liang 
Signed-off-by: Chao Gao 
Reviewed-by: Kevin Tian 
Signed-off-by: Christoph Hellwig

dma-mapping: move pgprot_decrypted out of dma_pgprot

2022-04-01T04:46:51+00:00

pgprot_decrypted is used by AMD SME systems to allow access to memory
that was set to not encrypted using set_memory_decrypted.  That only
happens for dma-direct memory as the IOMMU solves the addressing
challenges for the encryption bit using its own remapping.

Move the pgprot_decrypted call out of dma_pgprot which is also used
by the IOMMU mappings and into dma-direct so that it is only used with
memory that was set decrypted.

Fixes: f5ff79fddf0e ("dma-mapping: remove CONFIG_DMA_REMAP")
Reported-by: Alex Xu (Hello71) 
Signed-off-by: Christoph Hellwig 
Tested-by: Alex Xu (Hello71)

Merge tag 'dma-mapping-5.18' of git://git.infradead.org/users/hch/dma-mapping

2022-03-29T15:50:14+00:00

Pull dma-mapping updates from Christoph Hellwig:

 - do not zero buffer in set_memory_decrypted (Kirill A. Shutemov)

 - fix return value of dma-debug __setup handlers (Randy Dunlap)

 - swiotlb cleanups (Robin Murphy)

 - remove most remaining users of the pci-dma-compat.h API
   (Christophe JAILLET)

 - share the ABI header for the DMA map_benchmark with userspace
   (Tian Tao)

 - update the maintainer for DMA MAPPING BENCHMARK (Xiang Chen)

 - remove CONFIG_DMA_REMAP (me)

* tag 'dma-mapping-5.18' of git://git.infradead.org/users/hch/dma-mapping:
  dma-mapping: benchmark: extract a common header file for map_benchmark definition
  dma-debug: fix return value of __setup handlers
  dma-mapping: remove CONFIG_DMA_REMAP
  media: v4l2-pci-skeleton: Remove usage of the deprecated "pci-dma-compat.h" API
  rapidio/tsi721: Remove usage of the deprecated "pci-dma-compat.h" API
  sparc: Remove usage of the deprecated "pci-dma-compat.h" API
  agp/intel: Remove usage of the deprecated "pci-dma-compat.h" API
  alpha: Remove usage of the deprecated "pci-dma-compat.h" API
  MAINTAINERS: update maintainer list of DMA MAPPING BENCHMARK
  swiotlb: simplify array allocation
  swiotlb: tidy up includes
  swiotlb: simplify debugfs setup
  swiotlb: do not zero buffer in set_memory_decrypted()

Reinstate some of "swiotlb: rework "fix info leak with DMA_FROM_DEVICE""

2022-03-28T18:37:05+00:00

Halil Pasic points out [1] that the full revert of that commit (revert
in bddac7c1e02b), and that a partial revert that only reverts the
problematic case, but still keeps some of the cleanups is probably
better.  

And that partial revert [2] had already been verified by Oleksandr
Natalenko to also fix the issue, I had just missed that in the long
discussion.

So let's reinstate the cleanups from commit aa6f8dcbab47 ("swiotlb:
rework "fix info leak with DMA_FROM_DEVICE""), and effectively only
revert the part that caused problems.

Link: https://lore.kernel.org/all/20220328013731.017ae3e3.pasic@linux.ibm.com/ [1]
Link: https://lore.kernel.org/all/20220324055732.GB12078@lst.de/ [2]
Link: https://lore.kernel.org/all/4386660.LvFx2qVVIh@natalenko.name/ [3]
Suggested-by: Halil Pasic 
Tested-by: Oleksandr Natalenko 
Cc: Christoph Hellwig" 
Signed-off-by: Linus Torvalds

Revert "swiotlb: rework "fix info leak with DMA_FROM_DEVICE""

2022-03-26T17:42:04+00:00

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 
Reported-by: Olha Cherevyk 
Cc: Halil Pasic 
Cc: Christoph Hellwig 
Cc: Kalle Valo 
Cc: Robin Murphy 
Cc: Toke Høiland-Jørgensen 
Cc: Maxime Bizon 
Cc: Johannes Berg 
Signed-off-by: Linus Torvalds

Merge tag 'arm-soc-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc

2022-03-24T01:20:09+00:00

Pull ARM SoC updates from Arnd Bergmann:
 "SoC specific code is generally used for older platforms that don't
  (yet) use device tree to do the same things.

   - Support is added for i.MXRT10xx, a Cortex-M7 based microcontroller
     from NXP. At the moment this is still incomplete as other portions
     are merged through different trees.

   - Long abandoned support for running NOMMU ARMv4 or ARMv5 platforms
     gets removed, now the Arm NOMMU platforms are limited to the
     Cortex-M family of microcontrollers

   - Two old PXA boards get removed, along with corresponding driver
     bits.

   - Continued cleanup of the Intel IXP4xx platforms, removing some
     remnants of the old board files.

   - Minor Cleanups and fixes for Orion, PXA, MMP, Mstar, Samsung

   - CPU idle support for AT91

   - A system controller driver for Polarfire"

* tag 'arm-soc-5.18' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc: (29 commits)
  ARM: remove support for NOMMU ARMv4/v5
  ARM: PXA: fix up decompressor code
  soc: microchip: make mpfs_sys_controller_put static
  ARM: pxa: remove Intel Imote2 and Stargate 2 boards
  ARM: mmp: Fix failure to remove sram device
  ARM: mstar: Select ARM_ERRATA_814220
  soc: add microchip polarfire soc system controller
  ARM: at91: Kconfig: select PM_OPP
  ARM: at91: PM: add cpu idle support for sama7g5
  ARM: at91: ddr: fix typo to align with datasheet naming
  ARM: at91: ddr: align macro definitions
  ARM: at91: ddr: remove CONFIG_SOC_SAMA7 dependency
  ARM: ixp4xx: Convert to SPARSE_IRQ and P2V
  ARM: ixp4xx: Drop all common code
  ARM: ixp4xx: Drop custom DMA coherency and bouncing
  ARM: ixp4xx: Remove feature bit accessors
  net: ixp4xx_hss: Check features using syscon
  net: ixp4xx_eth: Drop platform data support
  soc: ixp4xx-npe: Access syscon regs using regmap
  soc: ixp4xx: Add features from regmap helper
  ...

cma: factor out minimum alignment requirement

2022-03-22T22:57:05+00:00

Patch series "mm: enforce pageblock_order < MAX_ORDER".

Having pageblock_order >= MAX_ORDER seems to be able to happen in corner
cases and some parts of the kernel are not prepared for it.

For example, Aneesh has shown [1] that such kernels can be compiled on
ppc64 with 64k base pages by setting FORCE_MAX_ZONEORDER=8, which will
run into a WARN_ON_ONCE(order >= MAX_ORDER) in comapction code right
during boot.

We can get pageblock_order >= MAX_ORDER when the default hugetlb size is
bigger than the maximum allocation granularity of the buddy, in which
case we are no longer talking about huge pages but instead gigantic
pages.

Having pageblock_order >= MAX_ORDER can only make alloc_contig_range()
of such gigantic pages more likely to succeed.

Reliable use of gigantic pages either requires boot time allcoation or
CMA, no need to overcomplicate some places in the kernel to optimize for
corner cases that are broken in other areas of the kernel.

This patch (of 2):

Let's enforce pageblock_order < MAX_ORDER and simplify.

Especially patch #1 can be regarded a cleanup before:
	[PATCH v5 0/6] Use pageblock_order for cma and alloc_contig_range
	alignment. [2]

[1] https://lkml.kernel.org/r/87r189a2ks.fsf@linux.ibm.com
[2] https://lkml.kernel.org/r/20220211164135.1803616-1-zi.yan@sent.com

Link: https://lkml.kernel.org/r/20220214174132.219303-2-david@redhat.com
Signed-off-by: David Hildenbrand 
Reviewed-by: Zi Yan 
Acked-by: Rob Herring 
Cc: Aneesh Kumar K.V 
Cc: Michael Ellerman 
Cc: Benjamin Herrenschmidt 
Cc: Paul Mackerras 
Cc: Frank Rowand 
Cc: Michael S. Tsirkin 
Cc: Christoph Hellwig 
Cc: Marek Szyprowski 
Cc: Robin Murphy 
Cc: Minchan Kim 
Cc: Vlastimil Babka 
Cc: John Garry via iommu 

Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

dma-mapping: benchmark: extract a common header file for map_benchmark definition

2022-03-10T06:41:14+00:00

kernel/dma/map_benchmark.c and selftests/dma/dma_map_benchmark.c
have duplicate map_benchmark definitions, which tends to lead to
inconsistent changes to map_benchmark on both sides, extract a
common header file to avoid this problem.

Signed-off-by: Tian Tao 
Acked-by: Barry Song 
Reviewed-by: Shuah Khan 
Signed-off-by: Christoph Hellwig

swiotlb: rework "fix info leak with DMA_FROM_DEVICE"

2022-03-07T19:26:02+00:00

Unfortunately, we ended up merging an old version of the patch "fix info
leak with DMA_FROM_DEVICE" instead of merging the latest one. Christoph
(the swiotlb maintainer), he asked me to create an incremental fix
(after I have pointed this out the mix up, and asked him for guidance).
So here we go.

The main differences between what we got and what was agreed are:
* swiotlb_sync_single_for_device is also required to do an extra bounce
* We decided not to introduce DMA_ATTR_OVERWRITE until we have exploiters
* The implantation of DMA_ATTR_OVERWRITE is flawed: DMA_ATTR_OVERWRITE
  must take precedence over DMA_ATTR_SKIP_CPU_SYNC

Thus this patch removes DMA_ATTR_OVERWRITE, and makes
swiotlb_sync_single_for_device() bounce unconditionally (that is, also
when dir == DMA_TO_DEVICE) in order do avoid synchronising back stale
data from the swiotlb buffer.

Let me note, that if the size used with dma_sync_* API is less than the
size used with dma_[un]map_*, under certain circumstances we may still
end up with swiotlb not being transparent. In that sense, this is no
perfect fix either.

To get this bullet proof, we would have to bounce the entire
mapping/bounce buffer. For that we would have to figure out the starting
address, and the size of the mapping in
swiotlb_sync_single_for_device(). While this does seem possible, there
seems to be no firm consensus on how things are supposed to work.

Signed-off-by: Halil Pasic 
Fixes: ddbd89deb7d3 ("swiotlb: fix info leak with DMA_FROM_DEVICE")
Cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig 
Signed-off-by: Linus Torvalds

dma-debug: fix return value of __setup handlers

2022-03-03T11:01:45+00:00

When valid kernel command line parameters
  dma_debug=off dma_debug_entries=100
are used, they are reported as Unknown parameters and added to init's
environment strings, polluting it.

  Unknown kernel command line parameters "BOOT_IMAGE=/boot/bzImage-517rc5
    dma_debug=off dma_debug_entries=100", will be passed to user space.

and

 Run /sbin/init as init process
   with arguments:
     /sbin/init
   with environment:
     HOME=/
     TERM=linux
     BOOT_IMAGE=/boot/bzImage-517rc5
     dma_debug=off
     dma_debug_entries=100

Return 1 from these __setup handlers to indicate that the command line
option has been handled.

Fixes: 59d3daafa1726 ("dma-debug: add kernel command line parameters")
Signed-off-by: Randy Dunlap 
Reported-by: Igor Zhbanov 
Link: lore.kernel.org/r/64644a2f-4a20-bab3-1e15-3b2cdd0defe3@omprussia.ru
Cc: Joerg Roedel 
Cc: Christoph Hellwig 
Cc: Marek Szyprowski 
Cc: iommu@lists.linux-foundation.org
Cc: Robin Murphy 
Signed-off-by: Christoph Hellwig