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firmware: fw_base: add an acquire fence after the _boot_status wait loop #429

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firmware: fw_base: add an acquire fence after the _boot_status wait loop #429

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11 changes: 11 additions & 0 deletions firmware/fw_base.S
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Original file line number Diff line number Diff line change
Expand Up @@ -407,6 +407,17 @@ _wait_for_boot_hart:
div t2, t2, zero
div t2, t2, zero
bne t0, t1, _wait_for_boot_hart
/*
* Acquire: order the _boot_status load above before every later
* load (platform.hart_count, platform.hart_index2id, the scratch
* space, ...). The boot hart publishes with "fence rw, rw" before
* its store to _boot_status, but without a matching acquire here
* RVWMO lets a waiting hart that saw BOOT_STATUS_BOOT_HART_DONE
* still read pre-relocation values, e.g. the unrelocated
* platform.hart_index2id pointer, and fault through it before
* mtvec is set.
*/
fence r, rw

_start_warm:
/* Reset all registers except ra, a0, a1, a2, a3 and a4 for non-boot HART */
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