register: 0.878
TCG: 0.836
graphic: 0.731
device: 0.728
architecture: 0.663
mistranslation: 0.635
kernel: 0.577
performance: 0.568
semantic: 0.551
network: 0.544
permissions: 0.525
peripherals: 0.492
files: 0.482
socket: 0.467
ppc: 0.453
risc-v: 0.451
vnc: 0.421
user-level: 0.417
debug: 0.408
hypervisor: 0.399
i386: 0.398
PID: 0.398
boot: 0.390
arm: 0.373
VMM: 0.346
assembly: 0.341
KVM: 0.339
x86: 0.282
virtual: 0.270
--------------------
TCG: 0.974
x86: 0.931
register: 0.679
assembly: 0.573
debug: 0.193
architecture: 0.057
kernel: 0.048
virtual: 0.042
i386: 0.032
semantic: 0.022
files: 0.021
hypervisor: 0.018
arm: 0.012
device: 0.011
user-level: 0.008
network: 0.008
socket: 0.006
risc-v: 0.005
performance: 0.005
ppc: 0.004
PID: 0.003
boot: 0.003
peripherals: 0.003
permissions: 0.002
vnc: 0.001
graphic: 0.001
VMM: 0.001
mistranslation: 0.000
KVM: 0.000

TCG: mov to segment register is incorrectly emulated for AMD CPUs

In TCG mode, the effect of:

xorl %eax, %eax
movl %eax, %gs

is to mark the GS segment unusable and set its base to zero.  After doing this, reading MSR_GS_BASE will return zero and using a GS prefix in long mode will treat the GS base as zero.

This is correct for Intel CPUs but is incorrect for AMD CPUs.  On an AMD CPU, writing 0 to %gs using mov, pop, or (I think) lgs will leave the base unchanged.

To make it easier to use TCG to validate behavior on different CPUs, please consider changing the TCG behavior to match actual CPU behavior when emulating an AMD CPU.

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.]