Just got confirmation from HP regarding X2APIC and PROLIANT SERVERS
using Ubuntu Linux:
Before GEN8.. all Proliant Servers did NOT support X2APIC. They had
firmware saying OS to NOT use X2APIC (and OS started supporting this by
commit: 41750d3, already included in kernel 3.2). The thing is.. for
these servers, opting out from X2APIC made them to use XAPIC IRQ
remapping (not supported).
-----
So, for Proliant Servers BEFORE GEN8 the recommended cmdline is this:
"nox2apic intermap=off"
Obs: nox2apic might not be needed since firmware is saying for Linux to
optout from using x2apic. Anyway I prefer to recommend this flag to make
sure kernels before 3.2 still work (not the case here).
-----
AFTER GEN8 (inclusive), the firmware STILL says that X2APIC must not be
used, but they ARE indeed supported by GEN8 (DL360, DL380). So proper
cmdlines are:
"intremap=no_x2apic_optout" # let X2APIC enabled with IRQ remapping
OR
"nox2apic intermap=off" # disable X2APIC AND IRQ remapping
X2APIC for these machines ONLY differs from XAPIC in question of IRQ
remapping (easier to implement). The other difference, where x2apic is
capable of addressing more CPUs, is not needed cause # of CPUs is low
enough.
This points out to my last finding, regarding:
*** cdcd629869fabcd38ebd24a03b0a05ec1cbcafb0 x86: Fix and improve
cmpxchg_double{,_local}()
|__> !!!!!!!!!!!!!!!! fix several problems related to cmpxchg and 64bits
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
cmpxchg is where instruction pointer is at (looks like) on the analyzed
dump.
Problem here is that kernel version from the core was erased from
ddebs.ubuntu and I'm using the "next" ddeb version. So I'm saying this
is the "most likely" to be happening since I can't objdump binary used
by analyzed system.
Things to be done:
1) Provide hotfix with this fix: cdcd629869f
2) Wait for intel_idle problem observation
(https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1318551)
3) Recommend users either:
"intremap=no_x2apic_optout" OR "nox2apic intermap=off"
TOGETHER with "intel_idle.max_cstate=0"
until we fix intel_idle.
Thank you
Rafael Tinoco
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https://bugs.launchpad.net/bugs/1398497
Title:
HP Proliant Serverrs - DL360 and DL380 Gen8 - Precise Kernel Panic -
General Protection Fault
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