On Thu, Jul 23, 2020 at 03:18:42PM +0000, Alex Belits wrote:

On Thu, 2020-07-23 at 15:17 +0200, Thomas Gleixner wrote:

quoted

Without going into details of the individual patches, let me give you a
high level view of this series:

  1) Entry code handling:

     That's completely broken vs. the careful ordering and instrumentation
     protection of the entry code. You can't just slap stuff randomly
     into places which you think are safe w/o actually trying to understand
     why this code is ordered in the way it is.

     This clearly was never built and tested with any of the relevant
     debug options enabled. Both build and boot would have told you.

This is intended to avoid a race condition when entry or exit from isolation
happens at the same time as an event that requires synchronization. The idea
is, it is possible to insulate the core from all events while it is running
isolated task in userspace, it will receive those calls normally after
breaking isolation and entering kernel, and it will synchronize itself on
kernel entry.

'What does noinstr mean? and why do we have it" -- don't dare touch the
entry code until you can answer that.

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