Messages in this thread | | | From | Keno Fischer <> | Date | Sun, 17 Jun 2018 14:22:01 -0400 | Subject | Re: [RFC PATCH] x86/arch_prctl: Add ARCH_SET_XCR0 to mask XCR0 per-thread |
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> Almost difference in CPU behavior > between the replayer and the replayee.
Not sure what happened to this sentence. What I meant to say was:
Almost any difference in CPU behavior between the replayer and the replayee will cause problems for the determinism of the trace.
To elaborate on this, even if a register whose content differs between the recording and the replay, it can still cause problems down the line, e.g. if it is spilled to the stack and that stack address is then re-used later. In order for rr to work, we basically rely on the CPU behaving *exactly* the same during the record and the replay (down to counting performance counters the same). This works well, but there are corner cases (like this XCR0 one).
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