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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/1739413
parent904141bfb8d5385b75eb3b7afec1dcda89af65a7 (diff)
downloademulator-bug-study-225caa38269323af1bfc2daadff5ec8bd930747f.tar.gz
emulator-bug-study-225caa38269323af1bfc2daadff5ec8bd930747f.zip
add mailinglist scraper results
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+Hotplugged vcpu does not guarantee cpu compat mode(power8) on power9 host
+
+./ppc64-softmmu/qemu-system-ppc64 -version
+QEMU emulator version 2.11.50 (v2.11.0-254-gaf35267)
+
+1. Boot a power8 compat mode guest power9 HW.
+./ppc64-softmmu/qemu-system-ppc64 -machine pseries,accel=kvm,max-cpu-compat=power8 -m 4096 /home/sath/images/guest.qcow2 -smp 1,maxcpus=2 -serial /dev/pts/8 -monitor stdio -vga none -nographic
+QEMU 2.11.50 monitor - type 'help' for more information
+(qemu)
+
+2. Check for cpuinfo
+
+# cat /proc/cpuinfo
+processor : 0
+cpu : POWER8 (architected), altivec supported
+clock : 2200.000000MHz
+revision : 2.1 (pvr 004e 1201)
+
+timebase : 512000000
+platform : pSeries
+model : IBM pSeries (emulated by qemu)
+machine : CHRP IBM pSeries (emulated by qemu)
+MMU : Hash
+
+
+3. Run a small program invoking isa v3.0 instruction, it should complain 'Illegal instruction' as it is a power8 compat guest
+# cat 1.c
+#include <stdio.h>
+void main()
+ {
+ asm volatile (".long 0x7c0005e6");
+ }
+# ./a.out
+[ 59.352795] a.out[1741]: unhandled signal 4 at 0000000010000600 nip 0000000010000600 lr 00007fffb4da5080 code 1
+Illegal instruction
+
+4. Hotplug a vcpu
+(qemu) device_add host-spapr-cpu-core,id=core1,core-id=1
+(qemu) info cpus
+* CPU #0: nip=0xc0000000000de42c thread_id=113110
+ CPU #1: nip=0xc0000000000de42c thread_id=113348
+
+5. Try running the same program in the hotplugged vcpu and it does not complain as 'Illegal instruction'
+
+#taskset -c 1 ./a.out ----------------------NOK
+#
+
+# taskset -c 0 ./a.out
+[ 356.618031] a.out[1755]: unhandled signal 4 at 0000000010000600 nip 0000000010000600 lr 00007fffae7f5080 code 1
+Illegal instruction
+
+Upstream patch from David Gibson @ https://lists.nongnu.org/archive/html/qemu-devel/2018-01/msg00587.html
+
+David's patch has been included here:
+https://git.qemu.org/?p=qemu.git;a=commitdiff;h=51f84465dd985fc21589b2e
+
+