> > > > > > > > > > This part puzzles me in the pseudo-code. > > > > > > > > > > The version is read first: > > > > > > > > > > TMP_VER := DS:RDX[63:0]; > > > > > > > > > > Then there's MAC calculation, comparison, and finally this check: > > > > > > > > > > (* Check version before committing *) > > > > > IF (DS:RDX ≠ 0) > > > > > THEN #GP(0); > > > > > ELSE > > > > > DS:RDX := TMP_VER; > > > > > FI; > > > > > > > > > > For me it is a mystery what does zero the slot and in what condition > > > > > it would be non-zero. Perhaps the #GP refers anyway to this check? > > > > > > > We discussed this internally, and agree this part of pseudo code needs be > corrected/clarified. > > Here is what we think was going on when ELDU invoked with PCMD of all > zeros: ELDU would check if the PCMD.SECINFO.FLAGS.PT is 0 which indicates > that the page being loaded is a PT_SECS, and the PAGEINFO.SECS is not > zero, then the instruction will #GP(0). Thus, ELDU is behaving correctly > – it is an omission in the SDM pseudocode. > > The version checking code above also need be clarified because the VA slot > would be cleared at this point and TMP_VER should be zero. "VA slot would be cleared at this point" isn't accurate. The VA slot itself is still occupied at this point. The original TMP_VER before the decryption is the VA slot value stored by EWB, and after decryption it becomes 0, if the decryption is correct. The correct pseudo-code should be: IF (TMP_VER != 0) THEN #GP(0); ELSE DS:RDX = TMP_VER; FI; The check of TMP_VER against 0 is just an additional safe guard to make sure decryption didn't fail. -- Thanks, -Kai
