linux.git/kernel/dma, branch v5.17.6

dma-direct: avoid redundant memory sync for swiotlb

2022-04-20T07:36:27+00:00

commit 9e02977bfad006af328add9434c8bffa40e053bb upstream.

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 
Signed-off-by: Greg Kroah-Hartman

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

2022-04-08T11:58:59+00:00

commit 901c7280ca0d5e2b4a8929fbe0bfb007ac2a6544 upstream.

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 
Signed-off-by: Greg Kroah-Hartman

dma-debug: fix return value of __setup handlers

2022-04-08T11:58:26+00:00

[ Upstream commit 80e4390981618e290616dbd06ea190d4576f219d ]

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 
Signed-off-by: Sasha Levin

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

2022-04-08T11:57:12+00:00

commit bddac7c1e02ba47f0570e494c9289acea3062cc1 upstream.

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 
Signed-off-by: Greg Kroah-Hartman

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

swiotlb: fix info leak with DMA_FROM_DEVICE

2022-02-14T09:22:28+00:00

The problem I'm addressing was discovered by the LTP test covering
cve-2018-1000204.

A short description of what happens follows:
1) The test case issues a command code 00 (TEST UNIT READY) via the SG_IO
   interface with: dxfer_len == 524288, dxdfer_dir == SG_DXFER_FROM_DEV
   and a corresponding dxferp. The peculiar thing about this is that TUR
   is not reading from the device.
2) In sg_start_req() the invocation of blk_rq_map_user() effectively
   bounces the user-space buffer. As if the device was to transfer into
   it. Since commit a45b599ad808 ("scsi: sg: allocate with __GFP_ZERO in
   sg_build_indirect()") we make sure this first bounce buffer is
   allocated with GFP_ZERO.
3) For the rest of the story we keep ignoring that we have a TUR, so the
   device won't touch the buffer we prepare as if the we had a
   DMA_FROM_DEVICE type of situation. My setup uses a virtio-scsi device
   and the  buffer allocated by SG is mapped by the function
   virtqueue_add_split() which uses DMA_FROM_DEVICE for the "in" sgs (here
   scatter-gather and not scsi generics). This mapping involves bouncing
   via the swiotlb (we need swiotlb to do virtio in protected guest like
   s390 Secure Execution, or AMD SEV).
4) When the SCSI TUR is done, we first copy back the content of the second
   (that is swiotlb) bounce buffer (which most likely contains some
   previous IO data), to the first bounce buffer, which contains all
   zeros.  Then we copy back the content of the first bounce buffer to
   the user-space buffer.
5) The test case detects that the buffer, which it zero-initialized,
  ain't all zeros and fails.

One can argue that this is an swiotlb problem, because without swiotlb
we leak all zeros, and the swiotlb should be transparent in a sense that
it does not affect the outcome (if all other participants are well
behaved).

Copying the content of the original buffer into the swiotlb buffer is
the only way I can think of to make swiotlb transparent in such
scenarios. So let's do just that if in doubt, but allow the driver
to tell us that the whole mapped buffer is going to be overwritten,
in which case we can preserve the old behavior and avoid the performance
impact of the extra bounce.

Signed-off-by: Halil Pasic 
Signed-off-by: Christoph Hellwig

Merge tag 'hyperv-next-signed-20220114' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux

2022-01-16T13:53:00+00:00

Pull hyperv updates from Wei Liu:

 - More patches for Hyper-V isolation VM support (Tianyu Lan)

 - Bug fixes and clean-up patches from various people

* tag 'hyperv-next-signed-20220114' of git://git.kernel.org/pub/scm/linux/kernel/git/hyperv/linux:
  scsi: storvsc: Fix storvsc_queuecommand() memory leak
  x86/hyperv: Properly deal with empty cpumasks in hyperv_flush_tlb_multi()
  Drivers: hv: vmbus: Initialize request offers message for Isolation VM
  scsi: storvsc: Fix unsigned comparison to zero
  swiotlb: Add CONFIG_HAS_IOMEM check around swiotlb_mem_remap()
  x86/hyperv: Fix definition of hv_ghcb_pg variable
  Drivers: hv: Fix definition of hypercall input & output arg variables
  net: netvsc: Add Isolation VM support for netvsc driver
  scsi: storvsc: Add Isolation VM support for storvsc driver
  hyper-v: Enable swiotlb bounce buffer for Isolation VM
  x86/hyper-v: Add hyperv Isolation VM check in the cc_platform_has()
  swiotlb: Add swiotlb bounce buffer remap function for HV IVM

Merge branch 'akpm' (patches from Andrew)

2022-01-15T18:37:06+00:00

Merge misc updates from Andrew Morton:
 "146 patches.

  Subsystems affected by this patch series: kthread, ia64, scripts,
  ntfs, squashfs, ocfs2, vfs, and mm (slab-generic, slab, kmemleak,
  dax, kasan, debug, pagecache, gup, shmem, frontswap, memremap,
  memcg, selftests, pagemap, dma, vmalloc, memory-failure, hugetlb,
  userfaultfd, vmscan, mempolicy, oom-kill, hugetlbfs, migration, thp,
  ksm, page-poison, percpu, rmap, zswap, zram, cleanups, hmm, and
  damon)"

* emailed patches from Andrew Morton : (146 commits)
  mm/damon: hide kernel pointer from tracepoint event
  mm/damon/vaddr: hide kernel pointer from damon_va_three_regions() failure log
  mm/damon/vaddr: use pr_debug() for damon_va_three_regions() failure logging
  mm/damon/dbgfs: remove an unnecessary variable
  mm/damon: move the implementation of damon_insert_region to damon.h
  mm/damon: add access checking for hugetlb pages
  Docs/admin-guide/mm/damon/usage: update for schemes statistics
  mm/damon/dbgfs: support all DAMOS stats
  Docs/admin-guide/mm/damon/reclaim: document statistics parameters
  mm/damon/reclaim: provide reclamation statistics
  mm/damon/schemes: account how many times quota limit has exceeded
  mm/damon/schemes: account scheme actions that successfully applied
  mm/damon: remove a mistakenly added comment for a future feature
  Docs/admin-guide/mm/damon/usage: update for kdamond_pid and (mk|rm)_contexts
  Docs/admin-guide/mm/damon/usage: mention tracepoint at the beginning
  Docs/admin-guide/mm/damon/usage: remove redundant information
  Docs/admin-guide/mm/damon/usage: update for scheme quotas and watermarks
  mm/damon: convert macro functions to static inline functions
  mm/damon: modify damon_rand() macro to static inline function
  mm/damon: move damon_rand() definition into damon.h
  ...

dma/pool: create dma atomic pool only if dma zone has managed pages

2022-01-15T14:30:29+00:00

Currently three dma atomic pools are initialized as long as the relevant
kernel codes are built in.  While in kdump kernel of x86_64, this is not
right when trying to create atomic_pool_dma, because there's no managed
pages in DMA zone.  In the case, DMA zone only has low 1M memory
presented and locked down by memblock allocator.  So no pages are added
into buddy of DMA zone.  Please check commit f1d4d47c5851 ("x86/setup:
Always reserve the first 1M of RAM").

Then in kdump kernel of x86_64, it always prints below failure message:

 DMA: preallocated 128 KiB GFP_KERNEL pool for atomic allocations
 swapper/0: page allocation failure: order:5, mode:0xcc1(GFP_KERNEL|GFP_DMA), nodemask=(null),cpuset=/,mems_allowed=0
 CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.13.0-0.rc5.20210611git929d931f2b40.42.fc35.x86_64 #1
 Hardware name: Dell Inc. PowerEdge R910/0P658H, BIOS 2.12.0 06/04/2018
 Call Trace:
  dump_stack+0x7f/0xa1
  warn_alloc.cold+0x72/0xd6
  __alloc_pages_slowpath.constprop.0+0xf29/0xf50
  __alloc_pages+0x24d/0x2c0
  alloc_page_interleave+0x13/0xb0
  atomic_pool_expand+0x118/0x210
  __dma_atomic_pool_init+0x45/0x93
  dma_atomic_pool_init+0xdb/0x176
  do_one_initcall+0x67/0x320
  kernel_init_freeable+0x290/0x2dc
  kernel_init+0xa/0x111
  ret_from_fork+0x22/0x30
 Mem-Info:
 ......
 DMA: failed to allocate 128 KiB GFP_KERNEL|GFP_DMA pool for atomic allocation
 DMA: preallocated 128 KiB GFP_KERNEL|GFP_DMA32 pool for atomic allocations

Here, let's check if DMA zone has managed pages, then create
atomic_pool_dma if yes.  Otherwise just skip it.

Link: https://lkml.kernel.org/r/20211223094435.248523-3-bhe@redhat.com
Fixes: 6f599d84231f ("x86/kdump: Always reserve the low 1M when the crashkernel option is specified")
Signed-off-by: Baoquan He 
Reviewed-by: Christoph Hellwig 
Acked-by: John Donnelly  
Reviewed-by: David Hildenbrand 
Cc: Marek Szyprowski 
Cc: Robin Murphy 
Cc: Borislav Petkov 
Cc: Christoph Lameter 
Cc: David Laight 
Cc: David Rientjes 
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Joonsoo Kim 
Cc: Pekka Enberg 
Cc: Vlastimil Babka 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

swiotlb: Add CONFIG_HAS_IOMEM check around swiotlb_mem_remap()

2022-01-04T16:11:19+00:00

HAS_IOMEM option may not be selected on some platforms (e.g, s390) and
this will cause compilation failure due to missing memremap()
implementation.

Fix it by stubbing out swiotlb_mem_remap when CONFIG_HAS_IOMEM is not
set.

Reported-by: kernel test robot 
Signed-off-by: Tianyu Lan 
Acked-by: Christoph Hellwig 
Signed-off-by: Wei Liu