Re: [BUG][PATCH?] kvm: unhandled wrmsr: 0xc0000083

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Luca Tettamanti wrote:
> which enabled the compilation of code depending on TARGET_X86_64.
> Problems arise when the host is in 32 bit mode; Avi fixed part of the
> issue with d9ff68d1 (masking the LM bit when the host is 32 bit).
>
> The MSR issue is caused by load_regs (qemu/qemu-kvm.c); at line 304 (git
> current) you can see:
>
> #ifdef TARGET_X86_64
>     set_msr_entry(&msrs[n++], MSR_CSTAR,             env->cstar);
>     set_msr_entry(&msrs[n++], MSR_KERNELGSBASE,      env->kernelgsbase);
>     set_msr_entry(&msrs[n++], MSR_FMASK,             env->fmask);
>     set_msr_entry(&msrs[n++], MSR_LSTAR ,            env->lstar);
> #endif
>
> But the kernel side part (vmx.c) cannot handle those MSRs when using a
> 32 bit kernel (hence the "unhandled wrmsr").
>
> As a side note: MSC_CSTAR (syscall target for compat mode) is supported
> *only* on AMD processors (there's no syscall on Intel in 32 bit mode);
> is it safe to use it unconditionally? (AFAICS vmx.c would do wrmsrl,
> maybe it's not documented but supported?).
>
> In order to fix this bug I hijacked "lm_capable_kernel" (introduced by
> Avi) so that {load,save}_regs don't touch 64bit-only MSRs while the host
> is in 32bit mode:
>
>   

Good catch -- patch applied, thanks.

> get_msr_entry should be fine, cpu_save/cpu_load (used by savevm -
> qemu/vl.c) may need a similar fix.
>
> The patch stops the "unhandled wrmsr", but reboot is still not working
> (guest is stuck using 100% of the CPU). The last working userspace is
> KVM-28, and I tested it with recent kernel modules. Any idea on this
> one?
>   

That's around the time kvm moved to its own main loop (for smp), so it's 
not surprising there's breakage there.  I tested erboot at the time, but 
not with all guests.

-- 
error compiling committee.c: too many arguments to function


-------------------------------------------------------------------------
This SF.net email is sponsored by: Splunk Inc.
Still grepping through log files to find problems?  Stop.
Now Search log events and configuration files using AJAX and a browser.
Download your FREE copy of Splunk now >>  http://get.splunk.com/