Previously, we would keep sampling the CPU frequency until two subsequent
samples differed by at most 1 MHz. This could take several seconds, and would
unnecessarily delay boot.
Instead, if sampling is too unreliable, just give up and calculate the average
frequency from 10 samples. This is no worse than picking the frequency that
just happened to be returned twice in a row.
The fact that this method of sampling fails could indicate that there's a
problem with our performance counter implementation or timer interrupt,
but that's a separate issue...
Note: before we had a BOOLEAN parameter called StoreInstruction, but in reality it was not specifying whether the fault was from a store store instruction, but whether it was an access violation rather than a page-not-present fault. On x86 without PAE there are only 2 kinds of access violations: (1) Access of a kernel mode page from user mode, which is handled early and (2) access of a read-only (or COW) page with a writing instruction. Therefore we could get away with this, even though it relied on the wrong assumption that a fault, which was not a page-not-present-fault, was automatically a write access. This commit only changes one thing: we pass the full fault-code to MmAccessFault and handle the rest from there in exactly the same way as before. More changes are coming to make things clear.
