riscv: preserve fflags when rejecting a reserved frm value - #280
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carlosqwqqwq wants to merge 1 commit into
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riscv: preserve fflags when rejecting a reserved frm value#280carlosqwqqwq wants to merge 1 commit into
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purplesyringa
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Aug 12, 2026
| return; | ||
| // Invalid rounding mode written: keep the old FRM value per | ||
| // WARL semantics, but still apply the other fields of fcsr | ||
| new_fcsr = bit_replace(new_fcsr, 5, 3, old_frm); |
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Maybe reconstruct new_fcsr from the patched new_frm/new_fflags once at writeback so that this isn't a path uncovered by most tests?
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Thanks! Reworked: fcsr is now reconstructed from the patched frm/fflags once at writeback (vm->csr.fcsr = (new_fcsr & ~CSR_FCSR_MASK) | new_fflags | (new_frm << 5)), so the reserved-frm path shares the same writeback as every other path. Rebuilt cleanly and force-pushed.
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riscv: preserve fflags when rejecting a reserved frm value
Fixes #274
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Description
riscv_update_fcsr()currently returns before committing the writablefflagsfield when the incomingfrmvalue is reserved. Keep the old/WARLfrmvalue and continue applying the independentfflagsbits. The change is limited tosrc/cpu/riscv_csr.c; the probe and research logs are not part of the upstream change.Validation