diff options
author | Timothy M. Jones <tjones1@inf.ed.ac.uk> | 2010-03-25 12:43:52 +0000 |
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committer | Timothy M. Jones <tjones1@inf.ed.ac.uk> | 2010-03-25 12:43:52 +0000 |
commit | 6b293c73fd19b73758547e1bfbe38a23d1800747 (patch) | |
tree | 5f71b6976fd9d4f065f441c235d8420c2fbadb75 /src | |
parent | a2652a048aaba65302d5d191754d873fc94fb226 (diff) | |
download | gem5-6b293c73fd19b73758547e1bfbe38a23d1800747.tar.xz |
CPU: Added comments to address translation classes.
Diffstat (limited to 'src')
-rw-r--r-- | src/cpu/translation.hh | 64 |
1 files changed, 62 insertions, 2 deletions
diff --git a/src/cpu/translation.hh b/src/cpu/translation.hh index 33e810710..983a748cf 100644 --- a/src/cpu/translation.hh +++ b/src/cpu/translation.hh @@ -35,6 +35,16 @@ #include "sim/tlb.hh" +/** + * This class captures the state of an address translation. A translation + * can be split in two if the ISA supports it and the memory access crosses + * a page boundary. In this case, this class is shared by two data + * translations (below). Otherwise it is used by a single data translation + * class. When each part of the translation is finished, the finish + * function is called which will indicate whether the whole translation is + * completed or not. There are also functions for accessing parts of the + * translation state which deal with the possible split correctly. + */ class WholeTranslationState { protected: @@ -50,7 +60,10 @@ class WholeTranslationState uint64_t *res; BaseTLB::Mode mode; - /** Single translation state. */ + /** + * Single translation state. We set the number of outstanding + * translations to one and indicate that it is not split. + */ WholeTranslationState(RequestPtr _req, uint8_t *_data, uint64_t *_res, BaseTLB::Mode _mode) : outstanding(1), isSplit(false), mainReq(_req), sreqLow(NULL), @@ -60,7 +73,11 @@ class WholeTranslationState assert(mode == BaseTLB::Read || mode == BaseTLB::Write); } - /** Split translation state. */ + /** + * Split translation state. We copy all state into this class, set the + * number of outstanding translations to two and then mark this as a + * split translation. + */ WholeTranslationState(RequestPtr _req, RequestPtr _sreqLow, RequestPtr _sreqHigh, uint8_t *_data, uint64_t *_res, BaseTLB::Mode _mode) @@ -71,6 +88,13 @@ class WholeTranslationState assert(mode == BaseTLB::Read || mode == BaseTLB::Write); } + /** + * Finish part of a translation. If there is only one request then this + * translation is completed. If the request has been split in two then + * the outstanding count determines whether the translation is complete. + * In this case, flags from the split request are copied to the main + * request to make it easier to access them later on. + */ bool finish(Fault fault, int index) { @@ -89,6 +113,10 @@ class WholeTranslationState return outstanding == 0; } + /** + * Determine whether this translation produced a fault. Both parts of the + * translation must be checked if this is a split translation. + */ Fault getFault() const { @@ -102,36 +130,54 @@ class WholeTranslationState return NoFault; } + /** Remove all faults from the translation. */ void setNoFault() { faults[0] = faults[1] = NoFault; } + /** + * Check if this request is uncacheable. We only need to check the main + * request because the flags will have been copied here on a split + * translation. + */ bool isUncacheable() const { return mainReq->isUncacheable(); } + /** + * Check if this request is a prefetch. We only need to check the main + * request because the flags will have been copied here on a split + * translation. + */ bool isPrefetch() const { return mainReq->isPrefetch(); } + /** Get the physical address of this request. */ Addr getPaddr() const { return mainReq->getPaddr(); } + /** + * Get the flags associated with this request. We only need to access + * the main request because the flags will have been copied here on a + * split translation. + */ unsigned getFlags() { return mainReq->getFlags(); } + /** Delete all requests that make up this translation. */ void deleteReqs() { @@ -143,6 +189,16 @@ class WholeTranslationState } }; + +/** + * This class represents part of a data address translation. All state for + * the translation is held in WholeTranslationState (above). Therefore this + * class does not need to know whether the translation is split or not. The + * index variable determines this but is simply passed on to the state class. + * When this part of the translation is completed, finish is called. If the + * translation state class indicate that the whole translation is complete + * then the execution context is informed. + */ template <class ExecContext> class DataTranslation : public BaseTLB::Translation { @@ -163,6 +219,10 @@ class DataTranslation : public BaseTLB::Translation { } + /** + * Finish this part of the translation and indicate that the whole + * translation is complete if the state says so. + */ void finish(Fault fault, RequestPtr req, ThreadContext *tc, BaseTLB::Mode mode) |