opensbi.git/lib/sbi/sbi_scratch.c, branch master

lib: sbi: Set the scratch allocation to alignment to cacheline size

2025-04-24T03:53:47Z

Set the scratch allocation alignment to cacheline size specified by riscv,cbom-block-size in the DTS file to avoid two atomic variables from the same cache line causing livelock on some platforms. If the cacheline is not specified, we set it a default value. Signed-off-by: Raj Vishwanathan Reviewed-by: Anup Patel Reviewed-by: Samuel Holland Link: https://lore.kernel.org/r/20250423225045.267983-1-Raj.Vishwanathan@gmail.com Signed-off-by: Anup Patel

lib: sbi: Use sbi_hart_count() and sbi_for_each_hartindex()

2025-03-24T12:27:20Z

Simplify the code and improve consistency by using the new macros where possible. sbi_hart_count() obsoletes sbi_scratch_last_hartindex(). Signed-off-by: Samuel Holland Reviewed-by: Anup Patel

lib: sbi_scratch: Add sbi_hart_count() and for_each_hartindex()

2025-03-24T12:26:08Z

There is currently no helper for iterating through the harts in a system, and code must choose between sbi_scratch_last_hartindex() and sbi_platform_hart_count() for the loop condition. sbi_scratch_last_hartindex() has unusual semantics, leading to the likelihood of off-by-one errors, and sbi_platform_hart_count() is provided by the platform and so may not be properly bounded. Add a new helper which definitively reports the number of harts managed by this OpenSBI instance, i.e. the number of valid hart indexes, and a convenient iterator macro. Signed-off-by: Samuel Holland Reviewed-by: Anup Patel

lib: sbi_scratch: Optimize hartid and scratch lookup

2025-03-24T12:26:05Z

The compiler generates much better code for sbi_hartindex_to_hartid() and sbi_hartindex_to_scratch() when using a constant for the bounds check. This works out nicely because the underlying arrays are already a constant size, so the only change needed is to fill the remainder of each array with the appropriate default/out-of-bounds value. The ellipsis in the designated initializer is a GCC extension (also supported by Clang), but avoids runtime initialization of the array. Signed-off-by: Samuel Holland Reviewed-by: Anup Patel

lib: sbi_scratch: Apply bounds check to platform hart_count

2025-03-24T12:26:04Z

The internal limit on the number of harts is SBI_HARTMASK_MAX_BITS, as this value determines the size of various bitmaps and arrays (including hartindex_to_hartid_table and hartindex_to_scratch_table). Clamp the value provided by the platform, and drop the extra array element. Update the documentation to indicate that hart_index2id must be sized based on hart_count, and that hart indexes must be contiguous. As of commit 5e90e54a1a53 ("lib: utils:Check that hartid is valid"), there is no restriction on the valid hart ID values. Signed-off-by: Samuel Holland Reviewed-by: Anup Patel

lib: sbi: Remove sbi_scratch_last_hartid() macro

2023-09-24T06:11:54Z

The sbi_scratch_last_hartid() macro is not of much use on platforms with really sparse hartids so let us replace use of this macro with other approaches. Signed-off-by: Anup Patel

lib: sbi: Introduce HART index in sbi_scratch

2023-09-24T06:09:21Z

We introduce HART index and related helper functions in sbi_scratch where HART index is contiguous and each HART index maps to a physical HART id such that 0 <= HART index and HART index < SBI_HARTMASK_MAX_BITS. The HART index to HART id mapping follows the index2id mapping provided by the platform. If the platform does not provide index2id mapping then identity mapping is assumed. Signed-off-by: Anup Patel

lib: sbi: Print scratch size and usage at boot time

2023-06-05T10:16:22Z

The scratch space being a scarce resource so let us print it's size and usage at boot time. Signed-off-by: Anup Patel Reviewed-by: Andrew Jones

lib: sbi_scratch: Optimize the alignment code for alloc size

2023-04-06T10:30:45Z

Signed-off-by: Xiang W Reviewed-by: Anup Patel

lib: sbi_scratch: zero out scratch memory on all harts

2021-06-11T08:29:48Z

In sbi_scratch_init() we determine the last hart. The index of the last hart cannot exceed SBI_HARTMASK_MAX_BITS - 1. We should not initialize last_hartid_having_scratch to a higher number to avoid buffer overflows when using this value before calling sbi_scratch_init(). When allocating scratch memory in sbi_scratch_alloc_offset() we zero out the allocated memory for all harts except for the last one. We should not skip the last hart. Signed-off-by: Heinrich Schuchardt Reviewed-by: Anup Patel