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[iobuf] Ensure I/O buffer data sits within unshared cachelines

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On platforms where DMA devices are not in the same coherency domain as
the CPU cache, we must ensure that DMA I/O buffers do not share
cachelines with other data.

Align the start and end of I/O buffers to IOB_ZLEN, which is larger
than any cacheline size we expect to encounter.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2025-07-07 13:21:24 +01:00
parent c21443f0b9
commit 19f1407ad9
3 changed files with 31 additions and 21 deletions
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src/tests/iobuf_test.c
+7 -1
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@@ -62,7 +62,7 @@ static inline void alloc_iob_okx ( size_t len, size_t align, size_t offset,
"offset %#zx\n", iobuf, virt_to_phys ( iobuf->data ),
iob_tailroom ( iobuf ), len, align, offset );
/* Validate requested length and alignment */
/* Validate requested length and data alignment */
okx ( ( ( ( intptr_t ) iobuf ) & ( __alignof__ ( *iobuf ) - 1 ) ) == 0,
file, line );
okx ( iob_tailroom ( iobuf ) >= len, file, line );
@@ -70,6 +70,12 @@ static inline void alloc_iob_okx ( size_t len, size_t align, size_t offset,
( ( virt_to_phys ( iobuf->data ) & ( align - 1 ) ) ==
( offset & ( align - 1 ) ) ) ), file, line );
/* Validate overall buffer alignment */
okx ( ( ( ( intptr_t ) iobuf->head ) & ( IOB_ZLEN - 1 ) ) == 0,
file, line );
okx ( ( ( ( intptr_t ) iobuf->end ) & ( IOB_ZLEN - 1 ) ) == 0,
file, line );
/* Overwrite entire content of I/O buffer (for Valgrind) */
memset ( iob_put ( iobuf, len ), 0x55, len );