Introduced in 0c54ac, "hw/riscv: add RISC-V IOMMU base emulation"
../hw/riscv/riscv-iommu.c:187:17: error: redefinition of '_pext_u64'
187 | static uint64_t _pext_u64(uint64_t val, uint64_t ext)
| ^
D:/a/_temp/msys64/clang64/lib/clang/18/include/bmi2intrin.h:217:1: note:
previous definition is here
217 | _pext_u64(unsigned long long __X, unsigned long long __Y)
| ^
After a conversation on the mailing list, it was decided to rename and
add a comment for this function.
Signed-off-by: Pierrick Bouvier <pierrick.bouv...@linaro.org>
---
hw/riscv/riscv-iommu.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/hw/riscv/riscv-iommu.c b/hw/riscv/riscv-iommu.c
index feb650549ac..12f01a75f5d 100644
--- a/hw/riscv/riscv-iommu.c
+++ b/hw/riscv/riscv-iommu.c
@@ -183,8 +183,25 @@ static void riscv_iommu_pri(RISCVIOMMUState *s,
}
}
-/* Portable implementation of pext_u64, bit-mask extraction. */
-static uint64_t _pext_u64(uint64_t val, uint64_t ext)
+/*
+ * Discards all bits from 'val' whose matching bits in the same
+ * positions in the mask 'ext' are zeros, and packs the remaining
+ * bits from 'val' contiguously at the least-significant end of the
+ * result, keeping the same bit order as 'val' and filling any
+ * other bits at the most-significant end of the result with zeros.
+ *
+ * For example, for the following 'val' and 'ext', the return 'ret'
+ * will be:
+ *
+ * val = a b c d e f g h
+ * ext = 1 0 1 0 0 1 1 0
+ * ret = 0 0 0 0 a c f g
+ *
+ * This function, taken from the riscv-iommu 1.0 spec, section 2.3.3
+ * "Process to translate addresses of MSIs", is similar to bit manip
+ * function PEXT (Parallel bits extract) from x86.
+ */
+static uint64_t riscv_iommu_pext_u64(uint64_t val, uint64_t ext)
{
uint64_t ret = 0;
uint64_t rot = 1;
@@ -528,7 +545,7 @@ static MemTxResult riscv_iommu_msi_write(RISCVIOMMUState *s,
int cause;
/* Interrupt File Number */
- intn = _pext_u64(PPN_DOWN(gpa), ctx->msi_addr_mask);
+ intn = riscv_iommu_pext_u64(PPN_DOWN(gpa), ctx->msi_addr_mask);
if (intn >= 256) {
/* Interrupt file number out of range */
res = MEMTX_ACCESS_ERROR;
--
2.39.5
