On Tue, Aug 23, 2016 at 11:38:41AM +0100, Lorenzo Pieralisi wrote: > On Mon, Aug 22, 2016 at 05:38:31PM -0700, Stephen Boyd wrote: > > [...] > > > This all comes about because the firmware generates a session id > > for the SMC call and jams it in x6. The assembly on the > > non-secure side is written with a tight loop around the smc > > instruction so that when the return value indicates > > "interrupted", x6 is kept intact and the non-secure OS can jump > > back to the secure OS without register reloading. Perhaps > > referring to x6 as result value is not correct because it's > > really a session id that's irrelevant once the smc call > > completes. > > Sorry I missed this bit. The session id is _generated_ by secure > firmware (probably only when the value passed in x6 == 0 (?)) > and actually returned to the caller so that subsequent (interrupted) > calls can re-issue the same value, is that correct ?
Yes, that is exactly what is going on. You always pass in 0 for the first call. If the call is interrupted and needs to be re-executed, you will get a specific result in a0 that tells you to redo the call using x6 as your session ID. > > If that's the case the value in x6 is a result value from an SMCCC > perspective and your current FW is not SMCCC compliant. Should we then write our own ASM snippet to do exactly what we want? It'd be the same as the arm_smccc except with the extra str. I'm ok with that, I was just hoping to leverage the existing smccc code. The quirk also works well, except it costs everyone else 1 load and compare. Regards, Andy
