On Wed, Mar 31, 2021 at 12:53 PM Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
> But this whole annotation thing will require serious compiler support.
> We already have problems with compilers inlining functions and getting confused about attributes.
We added compiler annotation for user-level interrupt handlers.
I'm not aware of it failing, or otherwise being confused.
Why would compiler support for fast-signals be any more "serious"?
> An API like:
>
> if (get_amx()) {
> use AMX;
> } else {
> don’t;
> }
>
> Avoids this problem. And making XCR0 dynamic, for all its faults, at least helps force a degree of discipline on user code.
dynamic XCR0 breaks the installed base, I thought we had established that.
We've also established that when running in a VMM, every update to
XCR0 causes a VMEXIT.
I thought the goal was to allow new programs to have fast signal handlers.
By default, those fast signal handlers would have a stable state
image, and would
not inherit large architectural state on their stacks, and could thus
have minimal overhead on all hardware.
