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authorChristian Krinitsin <mail@krinitsin.com>2025-06-30 12:24:58 +0000
committerChristian Krinitsin <mail@krinitsin.com>2025-06-30 12:27:06 +0000
commit33606b41d35115f887ea688b1a16f2ff85bf2fe4 (patch)
tree406b2c7b19a087ba437c68f3dbf0b589fa1d6150 /results/scraper/launchpad-without-comments/1902451
parentadedf8771bc4de3113041ca21bd4d0d1c0014b6a (diff)
downloadqemu-analysis-33606b41d35115f887ea688b1a16f2ff85bf2fe4.tar.gz
qemu-analysis-33606b41d35115f887ea688b1a16f2ff85bf2fe4.zip
add launchpad bug reports without comments
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+incorrect cpuid feature detection
+
+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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