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authorChristian Krinitsin <mail@krinitsin.com>2025-05-30 14:51:13 +0000
committerChristian Krinitsin <mail@krinitsin.com>2025-05-30 14:51:13 +0000
commit225caa38269323af1bfc2daadff5ec8bd930747f (patch)
treee0a5fefde9ee100ba6f32fb36de6707490e4164e /mailinglist/output_launchpad/1774605
parent904141bfb8d5385b75eb3b7afec1dcda89af65a7 (diff)
downloademulator-bug-study-225caa38269323af1bfc2daadff5ec8bd930747f.tar.gz
emulator-bug-study-225caa38269323af1bfc2daadff5ec8bd930747f.zip
add mailinglist scraper results
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+PowerPC guest does not emulate L2 and L3 cache for KVM vCPUs
+
+PowerPC KVM guest does not emulate L2 and L2 caches for vCPU, it would be good to have them enabled if not any known issues/limitation already with PowerPC.
+
+Host Env:
+kernel: 4.17.0-rc7-00045-g0512e0134582
+qemu: v2.12.0-923-gc181ddaa17-dirty
+#libvirtd -V
+libvirtd (libvirt) 4.4.0
+
+
+Guest Kernel:
+# uname -a
+Linux atest-guest 4.17.0-rc7-00045-g0512e0134582 #9 SMP Fri Jun 1 02:55:50 EDT 2018 ppc64le ppc64le ppc64le GNU/Linux
+
+Guest:
+# lscpu
+Architecture: ppc64le
+Byte Order: Little Endian
+CPU(s): 16
+On-line CPU(s) list: 0-15
+Thread(s) per core: 8
+Core(s) per socket: 2
+Socket(s): 1
+NUMA node(s): 1
+Model: 2.1 (pvr 004b 0201)
+Model name: POWER8 (architected), altivec supported
+Hypervisor vendor: KVM
+Virtualization type: para
+L1d cache: 64K
+L1i cache: 32K
+NUMA node0 CPU(s): 0-15
+
+
+
+background: x86 enabling cpu L2 cache bydefault and L3 cache on demand for kvm guest
+and claims performance improvement as vcpus can be
+benefited with lesser `vmexits due to guest send IPIs.` with L3 cache enabled, below was patch for same.
+
+https://git.qemu.org/?p=qemu.git;a=commit;h=14c985cffa6cb177fc01a163d8bcf227c104718c
+
+Guest xml(cpu portion):
+
+...
+ <vcpu placement='static' current='16'>32</vcpu>
+ <resource>
+ <partition>/machine</partition>
+ </resource>
+ <os>
+ <type arch='ppc64le' machine='pseries-2.13'>hvm</type>
+ <kernel>/home/kvmci/linux/vmlinux</kernel>
+ <cmdline>root=/dev/sda2 rw console=tty0 console=ttyS0,115200 init=/sbin/init initcall_debug</cmdline>
+ <boot dev='hd'/>
+ </os>
+ <cpu mode='host-passthrough' check='none'>
+ <topology sockets='2' cores='2' threads='8'/>
+ </cpu>
+...
+
+
+Host lscpu:
+# lscpu
+Architecture: ppc64le
+Byte Order: Little Endian
+CPU(s): 80
+On-line CPU(s) list: 0,8,16,24,32,40,48,56,64,72
+Off-line CPU(s) list: 1-7,9-15,17-23,25-31,33-39,41-47,49-55,57-63,65-71,73-79
+Thread(s) per core: 1
+Core(s) per socket: 5
+Socket(s): 2
+NUMA node(s): 2
+Model: 2.1 (pvr 004b 0201)
+Model name: POWER8E (raw), altivec supported
+CPU max MHz: 3690.0000
+CPU min MHz: 2061.0000
+L1d cache: 64K
+L1i cache: 32K
+L2 cache: 512K
+L3 cache: 8192K
+NUMA node0 CPU(s): 0,8,16,24,32
+NUMA node1 CPU(s): 40,48,56,64,72
+
+
+The QEMU project is currently considering to move its bug tracking to
+another system. For this we need to know which bugs are still valid
+and which could be closed already. Thus we are setting older bugs to
+"Incomplete" now.
+
+If you still think this bug report here is valid, then please switch
+the state back to "New" within the next 60 days, otherwise this report
+will be marked as "Expired". Or please mark it as "Fix Released" if
+the problem has been solved with a newer version of QEMU already.
+
+Thank you and sorry for the inconvenience.
+
+[Expired for QEMU because there has been no activity for 60 days.]
+