linux-stable.git/kernel/dma/direct.c, branch v6.11

swiotlb: reduce swiotlb pool lookups

2024-07-10T05:59:03+00:00

With CONFIG_SWIOTLB_DYNAMIC enabled, each round-trip map/unmap pair
in the swiotlb results in 6 calls to swiotlb_find_pool(). In multiple
places, the pool is found and used in one function, and then must
be found again in the next function that is called because only the
tlb_addr is passed as an argument. These are the six call sites:

dma_direct_map_page:
 1. swiotlb_map -> swiotlb_tbl_map_single -> swiotlb_bounce

dma_direct_unmap_page:
 2. dma_direct_sync_single_for_cpu -> is_swiotlb_buffer
 3. dma_direct_sync_single_for_cpu -> swiotlb_sync_single_for_cpu ->
	swiotlb_bounce
 4. is_swiotlb_buffer
 5. swiotlb_tbl_unmap_single -> swiotlb_del_transient
 6. swiotlb_tbl_unmap_single -> swiotlb_release_slots

Reduce the number of calls by finding the pool at a higher level, and
passing it as an argument instead of searching again. A key change is
for is_swiotlb_buffer() to return a pool pointer instead of a boolean,
and then pass this pool pointer to subsequent swiotlb functions.

There are 9 occurrences of is_swiotlb_buffer() used to test if a buffer
is a swiotlb buffer before calling a swiotlb function. To reduce code
duplication in getting the pool pointer and passing it as an argument,
introduce inline wrappers for this pattern. The generated code is
essentially unchanged.

Since is_swiotlb_buffer() no longer returns a boolean, rename some
functions to reflect the change:

 * swiotlb_find_pool() becomes __swiotlb_find_pool()
 * is_swiotlb_buffer() becomes swiotlb_find_pool()
 * is_xen_swiotlb_buffer() becomes xen_swiotlb_find_pool()

With these changes, a round-trip map/unmap pair requires only 2 pool
lookups (listed using the new names and wrappers):

dma_direct_unmap_page:
 1. dma_direct_sync_single_for_cpu -> swiotlb_find_pool
 2. swiotlb_tbl_unmap_single -> swiotlb_find_pool

These changes come from noticing the inefficiencies in a code review,
not from performance measurements. With CONFIG_SWIOTLB_DYNAMIC,
__swiotlb_find_pool() is not trivial, and it uses an RCU read lock,
so avoiding the redundant calls helps performance in a hot path.
When CONFIG_SWIOTLB_DYNAMIC is *not* set, the code size reduction
is minimal and the perf benefits are likely negligible, but no
harm is done.

No functional change is intended.

Signed-off-by: Michael Kelley 
Reviewed-by: Petr Tesarik 
Signed-off-by: Christoph Hellwig

dma-direct: Leak pages on dma_set_decrypted() failure

2024-02-28T13:31:38+00:00

On TDX it is possible for the untrusted host to cause
set_memory_encrypted() or set_memory_decrypted() to fail such that an
error is returned and the resulting memory is shared. Callers need to
take care to handle these errors to avoid returning decrypted (shared)
memory to the page allocator, which could lead to functional or security
issues.

DMA could free decrypted/shared pages if dma_set_decrypted() fails. This
should be a rare case. Just leak the pages in this case instead of
freeing them.

Signed-off-by: Rick Edgecombe 
Signed-off-by: Christoph Hellwig

dma-mapping: don't store redundant offsets

2023-12-15T11:32:42+00:00

A bus_dma_region necessarily stores both CPU and DMA base addresses for
a range, so there's no need to also store the difference between them.

Signed-off-by: Robin Murphy 
Acked-by: Rob Herring 
Signed-off-by: Christoph Hellwig

dma-mapping: fix dma_addressing_limited() if dma_range_map can't cover all system RAM

2023-11-06T07:38:16+00:00

There is an unusual case that the range map covers right up to the top
of system RAM, but leaves a hole somewhere lower down. Then it prevents
the nvme device dma mapping in the checking path of phys_to_dma() and
causes the hangs at boot.

E.g. On an Armv8 Ampere server, the dsdt ACPI table is:
 Method (_DMA, 0, Serialized)  // _DMA: Direct Memory Access
            {
                Name (RBUF, ResourceTemplate ()
                {
                    QWordMemory (ResourceConsumer, PosDecode, MinFixed,
MaxFixed, Cacheable, ReadWrite,
                        0x0000000000000000, // Granularity
                        0x0000000000000000, // Range Minimum
                        0x00000000FFFFFFFF, // Range Maximum
                        0x0000000000000000, // Translation Offset
                        0x0000000100000000, // Length
                        ,, , AddressRangeMemory, TypeStatic)
                    QWordMemory (ResourceConsumer, PosDecode, MinFixed,
MaxFixed, Cacheable, ReadWrite,
                        0x0000000000000000, // Granularity
                        0x0000006010200000, // Range Minimum
                        0x000000602FFFFFFF, // Range Maximum
                        0x0000000000000000, // Translation Offset
                        0x000000001FE00000, // Length
                        ,, , AddressRangeMemory, TypeStatic)
                    QWordMemory (ResourceConsumer, PosDecode, MinFixed,
MaxFixed, Cacheable, ReadWrite,
                        0x0000000000000000, // Granularity
                        0x00000060F0000000, // Range Minimum
                        0x00000060FFFFFFFF, // Range Maximum
                        0x0000000000000000, // Translation Offset
                        0x0000000010000000, // Length
                        ,, , AddressRangeMemory, TypeStatic)
                    QWordMemory (ResourceConsumer, PosDecode, MinFixed,
MaxFixed, Cacheable, ReadWrite,
                        0x0000000000000000, // Granularity
                        0x0000007000000000, // Range Minimum
                        0x000003FFFFFFFFFF, // Range Maximum
                        0x0000000000000000, // Translation Offset
                        0x0000039000000000, // Length
                        ,, , AddressRangeMemory, TypeStatic)
                })

But the System RAM ranges are:
cat /proc/iomem |grep -i ram
90000000-91ffffff : System RAM
92900000-fffbffff : System RAM
880000000-fffffffff : System RAM
8800000000-bff5990fff : System RAM
bff59d0000-bff5a4ffff : System RAM
bff8000000-bfffffffff : System RAM
So some RAM ranges are out of dma_range_map.

Fix it by checking whether each of the system RAM resources can be
properly encompassed within the dma_range_map.

Signed-off-by: Jia He 
Signed-off-by: Christoph Hellwig

dma-direct: warn when coherent allocations aren't supported

2023-10-22T14:38:54+00:00

Log a warning once when dma_alloc_coherent fails because the platform
does not support coherent allocations at all.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Robin Murphy 
Reviewed-by: Greg Ungerer 
Tested-by: Greg Ungerer

dma-direct: simplify the use atomic pool logic in dma_direct_alloc

2023-10-22T14:38:54+00:00

The logic in dma_direct_alloc when to use the atomic pool vs remapping
grew a bit unreadable.  Consolidate it into a single check, and clean
up the set_uncached vs remap logic a bit as well.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Robin Murphy 
Reviewed-by: Greg Ungerer 
Tested-by: Greg Ungerer

dma-direct: add a CONFIG_ARCH_HAS_DMA_ALLOC symbol

2023-10-22T14:38:54+00:00

Instead of using arch_dma_alloc if none of the generic coherent
allocators are used, require the architectures to explicitly opt into
providing it.  This will used to deal with the case of m68knommu and
coldfire where we can't do any coherent allocations whatsoever, and
also makes it clear that arch_dma_alloc is a last resort.

Signed-off-by: Christoph Hellwig 
Reviewed-by: Robin Murphy 
Reviewed-by: Greg Ungerer 
Tested-by: Greg Ungerer

swiotlb: if swiotlb is full, fall back to a transient memory pool

2023-08-01T16:02:20+00:00

Try to allocate a transient memory pool if no suitable slots can be found
and the respective SWIOTLB is allowed to grow. The transient pool is just
enough big for this one bounce buffer. It is inserted into a per-device
list of transient memory pools, and it is freed again when the bounce
buffer is unmapped.

Transient memory pools are kept in an RCU list. A memory barrier is
required after adding a new entry, because any address within a transient
buffer must be immediately recognized as belonging to the SWIOTLB, even if
it is passed to another CPU.

Deletion does not require any synchronization beyond RCU ordering
guarantees. After a buffer is unmapped, its physical addresses may no
longer be passed to the DMA API, so the memory range of the corresponding
stale entry in the RCU list never matches. If the memory range gets
allocated again, then it happens only after a RCU quiescent state.

Since bounce buffers can now be allocated from different pools, add a
parameter to swiotlb_alloc_pool() to let the caller know which memory pool
is used. Add swiotlb_find_pool() to find the memory pool corresponding to
an address. This function is now also used by is_swiotlb_buffer(), because
a simple boundary check is no longer sufficient.

The logic in swiotlb_alloc_tlb() is taken from __dma_direct_alloc_pages(),
simplified and enhanced to use coherent memory pools if needed.

Note that this is not the most efficient way to provide a bounce buffer,
but when a DMA buffer can't be mapped, something may (and will) actually
break. At that point it is better to make an allocation, even if it may be
an expensive operation.

Signed-off-by: Petr Tesarik 
Reviewed-by: Greg Kroah-Hartman 
Signed-off-by: Christoph Hellwig

dma-mapping: name SG DMA flag helpers consistently

2023-06-19T23:19:22+00:00

sg_is_dma_bus_address() is inconsistent with the naming pattern of its
corresponding setters and its own kerneldoc, so take the majority vote and
rename it sg_dma_is_bus_address() (and fix up the missing underscores in
the kerneldoc too).  This gives us a nice clear pattern where SG DMA flags
are SG_DMA_, and the helpers for acting on them are
sg_dma__().

Link: https://lkml.kernel.org/r/20230612153201.554742-14-catalin.marinas@arm.com
Signed-off-by: Robin Murphy 
Signed-off-by: Catalin Marinas 
Reviewed-by: Christoph Hellwig 
Reviewed-by: Jerry Snitselaar 
Reviewed-by: Logan Gunthorpe 
  Link: https://lore.kernel.org/r/fa2eca2862c7ffc41b50337abffb2dfd2864d3ea.1685036694.git.robin.murphy@arm.com
Tested-by: Isaac J. Manjarres 
Cc: Alasdair Kergon 
Cc: Ard Biesheuvel 
Cc: Arnd Bergmann 
Cc: Daniel Vetter 
Cc: Greg Kroah-Hartman 
Cc: Herbert Xu 
Cc: Joerg Roedel 
Cc: Jonathan Cameron 
Cc: Jonathan Cameron 
Cc: Lars-Peter Clausen 
Cc: Marc Zyngier 
Cc: Mark Brown 
Cc: Mike Snitzer 
Cc: "Rafael J. Wysocki" 
Cc: Saravana Kannan 
Cc: Vlastimil Babka 
Cc: Will Deacon 
Signed-off-by: Andrew Morton

dma-direct: cleanup parameters to dma_direct_optimal_gfp_mask

2023-03-28T01:34:05+00:00

Since both callers of dma_direct_optimal_gfp_mask() pass
dev->coherent_dma_mask as the second argument, it is better to
remove that parameter altogether.

Not only is reducing number of parameters good for readability, but
the new function signature is also more logical: The optimal flags
depend only on data contained in struct device.

While touching this code, let's also rename phys_mask to phys_limit
in dma_direct_alloc_from_pool(), because it is indeed a limit.

Signed-off-by: Petr Tesarik 
Signed-off-by: Christoph Hellwig