** Also affects: linux (Ubuntu Bionic)
Importance: Undecided
Assignee: Ubuntu on IBM Power Systems Bug Triage (ubuntu-power-triage)
Status: New
** Changed in: linux (Ubuntu Bionic)
Status: New => Fix Committed
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https://bugs.launchpad.net/bugs/1765429
Title:
[regression] Ubuntu 18.04:[4.15.0-17-generic #18] KVM Guest Kernel:
meltdown: rfi/fallback displacement flush not enabled bydefault (kvm)
Status in The Ubuntu-power-systems project:
New
Status in linux package in Ubuntu:
Fix Committed
Status in linux source package in Bionic:
Fix Committed
Bug description:
---Problem Description---
4.15.0-17-generic #18-Ubuntu introduces newer knob to control enabling
rfi_flush to mitigate meltdown/spectre which is set to disable by default for
guest instead of enable.
#cat /sys/kernel/debug/powerpc/rfi_flush
0 --------------------------------------------------------------NOK
Expected:
/sys/kernel/debug/powerpc/rfi_flush should be 1 bydefault if guest has the
capability to mitigate.
---uname output---
Linux ubuntu 4.15.0-17-generic #18-Ubuntu SMP Mon Apr 16 21:16:36 UTC 2018
ppc64le ppc64le ppc64le GNU/Linux
---Additional Hardware Info---
power9 boston 2.2 (pvr 004e 1202), power8 tuleta 2.1 (pvr 004b 0201)
Machine Type = power9 boston 2.2 (pvr 004e 1202), power8 tuleta 2.1 (pvr 004b
0201)
---Steps to Reproduce---
Pre-requite:
FW version-
power9 boston: SUPERMICRO-P9DSU-V1.10-20180413-imp (that supports mitigation)
power8 tuleta: fips861/b0320a_1812.861 (that supports mitigation)
Host: 4.15.0-17-generic #18-Ubuntu
qemu: 1:2.11+dfsg-1ubuntu6
Guest: 4.15.0-17-generic #18-Ubuntu
Results of Power9 Host:
++++++++++++++++++
1) Boot a ubuntu 18.04 guest with latest kernel(4.15.0-17-generic #18)
with pseries-bionic-sxxm machine type, it boots with "no flush" i.e
/sys/kernel/debug/powerpc/rfi_flush = 0 which leads to below failure
in (l1d flush - syscall) unit test for meltdown.
# make tests
=========
Machine details from dmesg:
dmesg | grep -e 'pSeries machine' -e 'OPAL detected' -e rfi-fixups -e
rfi-flush
[ 0.000000] Using pSeries machine description
[ 0.000000] rfi-flush: fallback displacement flush available
[ 0.000000] rfi-flush: ori type flush available
[ 0.000000] rfi-flush: mttrig type flush available
[ 0.000000] rfi-flush: patched 9 locations (no flush)
=========
Running tests...
Testing mitigation for spectre (ii. indirect branch prediction)... PASS
(20000071 branches, 10000006 branch misses)
Testing mitigation for meltdown (l1d flush - syscall)... FAIL (132523 misses,
192000000 expected) [10/10 failures]
Testing mitigation for meltdown (l1d flush - userspace)... SKIP (!power8)
# uname -a
Linux ubuntu 4.15.0-17-generic #18-Ubuntu SMP Mon Apr 16 21:16:36 UTC 2018
ppc64le ppc64le ppc64le GNU/Linux
2) Once we enable rfi_flush i.e. /sys/kernel/debug/powerpc/rfi_flush = 1
manually the tests are passing fine,
#echo 1 > /sys/kernel/debug/powerpc/rfi_flush
# cat /sys/kernel/debug/powerpc/rfi_flush
1
# make tests
=========
Machine details from dmesg:
dmesg | grep -e 'pSeries machine' -e 'OPAL detected' -e rfi-fixups -e
rfi-flush
[ 0.000000] Using pSeries machine description
[ 0.000000] rfi-flush: fallback displacement flush available
[ 0.000000] rfi-flush: ori type flush available
[ 0.000000] rfi-flush: mttrig type flush available
[ 0.000000] rfi-flush: patched 9 locations (no flush)
[ 1502.627548] rfi-flush: patched 9 locations (ori+mttrig type flush)
=========
Running tests...
Testing mitigation for spectre (ii. indirect branch prediction)... PASS
(20000074 branches, 10000010 branch misses)
Testing mitigation for meltdown (l1d flush - syscall)... PASS (196010325
misses, 192000000 expected) [10/10 pass]
Testing mitigation for meltdown (l1d flush - userspace)... SKIP (!power8)
Results of Power8 Host:
+++++++++++++++++++
1)
#cat /sys/kernel/debug/powerpc/rfi_flush
0
# make tests
=========
Machine details from dmesg:
dmesg | grep -e 'pSeries machine' -e 'OPAL detected' -e rfi-fixups -e
rfi-flush
[ 0.000000] Using pSeries machine description
[ 0.000000] rfi-flush: fallback displacement flush available
[ 0.000000] rfi-flush: patched 9 locations (no flush)
=========
Running tests...
Testing mitigation for spectre (ii. indirect branch prediction)... PASS
(20000066 branches, 10000010 branch misses)
Testing mitigation for meltdown (l1d flush - syscall)... FAIL (150100 misses,
192000000 expected) [10/10 failures]
Testing mitigation for meltdown (l1d flush - userspace)... SKIP (!power8)
2)
#echo 1 > /sys/kernel/debug/powerpc/rfi_flush
#cat /sys/kernel/debug/powerpc/rfi_flush
1
# make tests
=========
Machine details from dmesg:
dmesg | grep -e 'pSeries machine' -e 'OPAL detected' -e rfi-fixups -e
rfi-flush
[ 0.000000] Using pSeries machine description
[ 0.000000] rfi-flush: fallback displacement flush available
[ 0.000000] rfi-flush: patched 9 locations (no flush)
[ 243.736201] rfi-flush: patched 9 locations (fallback displacement flush)
=========
Running tests...
Testing mitigation for spectre (ii. indirect branch prediction)... PASS
(20000054 branches, 10000008 branch misses)
Testing mitigation for meltdown (l1d flush - syscall)... PASS (195105463
misses, 192000000 expected) [10/10 pass]
Testing mitigation for meltdown (l1d flush - userspace)... SKIP (!power8)
# uname -a
Linux ubuntu 4.15.0-17-generic #18-Ubuntu SMP Mon Apr 16 21:16:36 UTC 2018
ppc64le ppc64le ppc64le GNU/Linux
== Breno Leitao ==
Patch sent to the mailing list already:
https://lists.ubuntu.com/archives/kernel-team/2018-April/091789.html
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu-power-systems/+bug/1765429/+subscriptions
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