APPLIED(B): [PATCH 0/1][SRU][B/OEM-B] Fix boot regression caused by a disabled PIT

[Khaled Elmously]

On 2020-06-12 19:51:59 , You-Sheng Yang wrote:
> BugLink: https://bugs.launchpad.net/bugs/1856387
> 
> [Impact]
> In bug 1840239, HPET is disabled on some systems for they caused TSC
> being marked unstable while it is not. This caused an regression as bug
> 1851216 that some systems may then hang at early, so a fix cherry picked
> back from v5.3-rc1. However, this fix also introduce yet another
> regression that some other users may hang at boot while PIT is diabled
> in the previous fix.
> 
> [Fix]
> Commit 979923871f69 ("x86/timer: Don't skip PIT setup when APIC is
> disabled or in legacy mode") from v5.6-rc1, also backported to v5.4.19
> and v5.5.3, fixes PIT setup in this case.
> 
> [Test Case]
> Simply boot a patch kernel on systems affected and it shouldn't hang.
> 
> [Regression Potential]
> Low. Stable patch and trivial backport.
> 
> [Other Info]
> The same fix for bug 1851216 was also backported to Disco and Eoan, but
> they were then fixed with this 979923871f69 commit backported in bug
> 1866858 and bug 1867051, which pulls v5.4 stable patches into Disco and
> Eoan correspondingly, leaving B/OEM-B the only victims so far.
> 
> Thomas Gleixner (1):
>   x86/timer: Don't skip PIT setup when APIC is disabled or in legacy
>     mode
> 
>  arch/x86/include/asm/apic.h     |  2 ++
>  arch/x86/include/asm/x86_init.h |  2 ++
>  arch/x86/kernel/apic/apic.c     | 23 ++++++++++++++++++-----
>  arch/x86/kernel/time.c          | 12 ++++++++++--
>  arch/x86/kernel/x86_init.c      |  1 +
>  arch/x86/xen/enlighten_pv.c     |  1 +
>  6 files changed, 34 insertions(+), 7 deletions(-)
> 
> -- 
> 2.27.0.rc0
> 
> 
> -- 
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