Messages in this thread | | | Date | Wed, 23 Aug 2023 03:27:28 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH 04/22] x86/srso: Fix SBPB enablement for spec_rstack_overflow=off |
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On Tue, Aug 22, 2023 at 02:59:01PM -0700, Josh Poimboeuf wrote: > Yeah, I had seen that. The combination of spectre_v2_user=on with > srso=off doesn't make a whole lot of sense, but... give the user what > they want and all. Which would presumably be IBPB *without* the SRSO > mitigation (aka SBPB).
Right.
> I don't think we need to worry about that, SBPB is >= fam19 but retbleed > is <= fam17. So either way (0x17 or 0x19) entry_ibpb() should do IBPB.
Right, and SBPB is possible only on family => 0x19 anyway which is not affected by retbleed.
I was worried that we might open some mitigation hole with the overwrite but it seems we're fine:
family 0x17: retbleed=ibpb, srso=off - is fine, can't do SBPB anyway family 0x19: retbleed=ibpb, srso=off - fine too, not affected by retbleed, can do SBPB
Unless I'm missing something again which is very likely, by now. ;-\
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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