riscv/rocket-chip
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Don't require that PMP ranges be aligned to access size

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e.g., if a range permits access to 0x0-0xb, allow 8-byte accesses 0x0-0x7.
This commit is contained in:
Andrew Waterman 2017-03-20 15:05:42 -07:00
parent 29e67279ba
commit 9e05200e51
1 changed files with 15 additions and 13 deletions
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28
src/main/scala/rocket/PMP.scala
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@ -56,18 +56,17 @@ class PMP(implicit p: Parameters) extends PMPReg {
}
}
private def boundMatch(x: UInt, lsbMask: UInt, lgMaxSize: Int) = {
if (lgMaxSize <= lgAlign) {
x < comparand
} else {
// break up the circuit; the MSB part will be CSE'd
val msbsLess = (x >> lgMaxSize) < (comparand >> lgMaxSize)
val msbsEqual = ((x >> lgMaxSize) ^ (comparand >> lgMaxSize)) === 0
val lsbsLess = x(lgMaxSize-1, 0) < (comparand(lgMaxSize-1, 0) & lsbMask(lgMaxSize-1, 0))
msbsLess || (msbsEqual && lsbsLess)
}
private def decomposedBoundMatch(xHi: UInt, xLo: UInt, lsbMask: UInt, lgMaxSize: Int) = {
val msbsLess = xHi < (comparand >> lgMaxSize)
val msbsEqual = (xHi ^ (comparand >> lgMaxSize)) === 0
val lsbsLess = xLo < (comparand(lgMaxSize-1, 0) & lsbMask(lgMaxSize-1, 0))
msbsLess || (msbsEqual && lsbsLess)
}
private def boundMatch(x: UInt, lsbMask: UInt, lgMaxSize: Int) =
if (lgMaxSize <= lgAlign) x < comparand
else decomposedBoundMatch(x >> lgMaxSize, x(lgMaxSize-1, 0), lsbMask, lgMaxSize)
private def lowerBoundMatch(x: UInt, lgSize: UInt, lgMaxSize: Int) =
!boundMatch(x, ((BigInt(1) << lgMaxSize) - 1).U << lgSize, lgMaxSize)
@ -99,9 +98,12 @@ class PMP(implicit p: Parameters) extends PMPReg {
!cfg.p(0) || Mux(cfg.a(1), rangeHomogeneous(x, pgLevel, lgMaxSize, prev), pow2Homogeneous(x, pgLevel))
// returns whether this matching PMP fully contains the access
def aligned(x: UInt, lgSize: UInt, lgMaxSize: Int, prev: PMP): Bool = {
val alignMask = ~(((BigInt(1) << lgMaxSize) - 1).U << lgSize)(lgMaxSize-1, 0)
val rangeAligned = (prev.comparand(lgMaxSize-1, 0) & alignMask) === 0 && (comparand(lgMaxSize-1, 0) & alignMask) === 0
def aligned(x: UInt, lgSize: UInt, lgMaxSize: Int, prev: PMP): Bool = if (lgMaxSize <= lgAlign) true.B else {
val lsbMask = ((BigInt(1) << lgMaxSize) - 1).U << lgSize
val alignMask = ~lsbMask(lgMaxSize-1, 0)
val lowerBoundOK = !prev.upperBoundMatch(x, lgMaxSize)
val upperBoundOK = decomposedBoundMatch(x >> lgMaxSize, x(lgMaxSize-1, 0) | alignMask, lsbMask, lgMaxSize)
val rangeAligned = lowerBoundOK && upperBoundOK
val pow2Aligned = (alignMask & ~mask(lgMaxSize-1, 0)) === 0
Mux(cfg.a(1), rangeAligned, pow2Aligned)
}