>
That's why my initial idea, as implemented in this RFC patchset, was to
stick with IBRS on Skylake, and use retpoline everywhere else. I'll
give you "garbage patches", but they weren't being "just mindlessly
sent around". If we're going to drop IBRS support and accept the
caveats, then let's do it as a conscious decision having seen what it
would look like, not just drop it quietly because poor Davey is too
scared that Linus might shout at him again. :)
>
If we can be done with the shouty part, I'd actually quite like to have
a sensible discussion about when, if ever, we do IBPB on context switch
(ptraceability and dumpable have both been suggested) and when, if
ever, we set STIPB in userspace.
Those seem relevant to the thread. That said - it's really a good read for a technical overview of the issues and patches.
I would recommend reading this response.
Here are some great excerpts:
> That's why my initial idea, as implemented in this RFC patchset, was to stick with IBRS on Skylake, and use retpoline everywhere else. I'll give you "garbage patches", but they weren't being "just mindlessly sent around". If we're going to drop IBRS support and accept the caveats, then let's do it as a conscious decision having seen what it would look like, not just drop it quietly because poor Davey is too scared that Linus might shout at him again. :)
> If we can be done with the shouty part, I'd actually quite like to have a sensible discussion about when, if ever, we do IBPB on context switch (ptraceability and dumpable have both been suggested) and when, if ever, we set STIPB in userspace.
Those seem relevant to the thread. That said - it's really a good read for a technical overview of the issues and patches.