Comment 34 for bug 1921754
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| Christian Ehrhardt (paelzer) wrote | #34 |
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35a32c5
(Get the code!)
Hi Sven,
as tom said on IRC - to some extend it is that Bionic didn't have a Rome chip definition yet, so the changes to add it to Rome do not 100% make sense there.
You have as part of similar fixes there already:
1. all kind of intel chips which were faster to provide that for 2.11 (in the stable tree of qemu)
root@b:~# qemu-system-x86_64 -cpu ? | grep -i ibrs
x86 Broadwell-IBRS Intel Core Processor (Broadwell, IBRS)
x86 Broadwell-
x86 Haswell-IBRS Intel Core Processor (Haswell, IBRS)
x86 Haswell-noTSX-IBRS Intel Core Processor (Haswell, no TSX, IBRS)
x86 IvyBridge-IBRS Intel Xeon E3-12xx v2 (Ivy Bridge, IBRS)
x86 Nehalem-IBRS Intel Core i7 9xx (Nehalem Core i7, IBRS update)
x86 SandyBridge-IBRS Intel Xeon E312xx (Sandy Bridge, IBRS update)
x86 Skylake-Client-IBRS Intel Core Processor (Skylake, IBRS)
x86 Skylake-Server-IBRS Intel Xeon Processor (Skylake, IBRS)
x86 Westmere-IBRS Westmere E56xx/L56xx/X56xx (IBRS update)
2. a generic EPYC chip which got what AMD first pushed for that was IBPB (mind all the characters - not the same)
root@b:~# qemu-system-x86_64 -cpu ? | grep -i epy
x86 EPYC-IBPB AMD EPYC Processor (with IBPB)
x86 EPYC AMD EPYC Processor
I rechecked if e.g. upstream stable of 2.11 since then changed things, but there is nothing in this regard. Nor did I see (in a very quick not thorough check) anyone else backporting it that far.
So you might say "can't I use shiny new chips and all of their feature with Bionic :-/", but for some applications stacks this is a common issue (the balance between stability vs staying new). And for those there often is a way between the obvious first recommendation "use a newer LTS and you get the newer bits" in the form of https:/
Back then when this bug came up these patches did neither make sense nor where in any way applicable to Bionic, one could take some more time to deeply re-evaluate this, but as I said above there are options already ...; I'm tempted to say that this should be spawned into a separate bug then to keep this one as-is reflecting only the efforts of the past.