ACK/Cmnt: [SRU][Xenial][PULL] Guests using IBRS incur a large performance penalty (LP: #1764956)

[Stefan Bader]

On 08.01.19 14:43, Stefan Bader wrote:
> On 19.12.18 11:03, Juerg Haefliger wrote:
>> git://git.launchpad.net/~juergh/+git/xenial-linux lp1764956-v2
> 
> 
> Glancing over the changes I noticed that "UBUNTU: SAUCE: x86/speculation:
> Cleanup IBPB runtime control handling" adds use of spec_ctrl_mutex but only
> "UBUNTU: SAUCE: x86/speculation: Cleanup IBRS runtime control handling" which
> follows next actually seems to declare it. In the end that does not matter only
> could make bisection a pain.
> 
> Minor pedantic nitbit: is not "UBUNTU: SAUCE: x86/speculation: Move RSB_CTXSW
> hunk" moving the hunk further down?
> 
> Apart from that the other changes roughly seemed to make sense but I have to
> admit that I went rather quickly over the non-SAUCE ones. The delta is just too
> big and I rely a bit on the successful testing.
> 
> So if fixing up the first 2 patches (which should be doable when applying)
> 
> Acked-by: Stefan Bader <stefan.bader at canonical.com>
> 
> 
Just to re-new my ack with the  patches which come before this pull request
applied before from the separate thread.

-Stefan

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