Messages in this thread | | | Date | Mon, 14 Aug 2023 12:34:37 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC][PATCH 12/17] x86/cpu: Rename original retbleed return thunk |
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On Sun, Aug 13, 2023 at 04:23:27PM +0100, Andrew.Cooper3@citrix.com wrote: > On 10/08/2023 2:02 pm, Peter Zijlstra wrote:
> > So BTC as a whole is the fact that AMD predicts the type of an > > instruction and then picks a predictor to predict the target of that > > instruction, no? > > No. > > "Branch Type Confusion" is the technical name AMD gave last year's > issue. Hence the name of the whitepaper about it, > https://www.amd.com/system/files/documents/technical-guidance-for-mitigating-branch-type-confusion.pdf
Bah, then what do we call the actual underlying issue that the AMD branch predictor starts by predicting the next instruction type -- before it has been decoded -- meaning it can predict it wrong, which then leads to a tons of other issues, including but not limited to:
SLS through JMP (or pretty much anything else) RET from BTB
?
Calling *THAT* branch-type-confusion makes a heap more sense to me.
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