[Expired for QEMU because there has been no activity for 60 days.]
** Changed in: qemu
Status: Incomplete => Expired
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https://bugs.launchpad.net/bugs/1902451
Title:
incorrect cpuid feature detection
Status in QEMU:
Expired
Bug description:
Hello,
I am currently developing a x64 kernel and I wanted to check through
cpuid if some features are available in the guest. When I try to
enable cpu features like vmcb_clean or constant_tsc qemu is saying
that my host doesn't support the requested features. However cat
/proc/cpuinfo tells a different story:
model name: AMD Ryzen 5 3500U
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov
pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext fxsr_opt pdpe1gb
rdtscp lm constant_tsc rep_good nopl nonstop_tsc cpuid extd_apicid aperfmperf
pni pclmulqdq monitor ssse3 fma cx16 sse4_1 sse4_2 movbe popcnt aes xsave avx
f16c rdrand lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse
3dnowprefetch osvw skinit wdt tce topoext perfctr_core perfctr_nb bpext
perfctr_llc mwaitx cpb hw_pstate sme pti ssbd sev ibpb vmmcall fsgsbase bmi1
avx2 smep bmi2 rdseed adx smap clflushopt sha_ni xsaveopt xsavec xgetbv1 xsaves
clzero irperf xsaveerptr arat npt lbrv svm_lock nrip_save tsc_scale vmcb_clean
flushbyasid decodeassists pausefilter pfthreshold avic v_vmsave_vmload vgif
overflow_recov succor smca
I also checked it myself by running cpuid and check the bits as in the
AMD Manual. Everything checks out but qemu still fails.
QEMU version: QEMU emulator version 4.2.0
$ qemu-system-x86_64 -cpu host,+vmcb_clean,enforce -enable-kvm -drive
format=raw,file=target/x86_64-os/debug/bootimage-my_kernel.bin -serial stdio
-display none
qemu-system-x86_64: warning: host doesn't support requested feature:
CPUID.8000000AH:EDX.vmcb-clean [bit 5]
qemu-system-x86_64: Host doesn't support requested features
or
$ qemu-system-x86_64 -cpu host,+constant_tsc,enforce -enable-kvm -drive
format=raw,file=target/x86_64-os/debug/bootimage-my_kernel.bin -serial stdio
-display none
qemu-system-x86_64: Property '.constant_tsc' not found
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