Re: [Xen-devel] VMX check in /xen/arch/x86/domain.c is invalid on x86-64 (at least AMD)

[Arun Sharma <arun.sharma@xxxxxxxxx>]

Jerone Young wrote:
> if (!(c->flags & ECF_VMX_GUEST))
>         if ( ((c->cpu_ctxt.cs & 3) == 0) ||
>              ((c->cpu_ctxt.ss & 3) == 0) )
>                 return -EINVAL;
>
> This check in /xen/arch/x86/domain.c (line 394) is invalid for AMD
> x86-64 as this field 1<<1 is a reserved field in the rflags (name for
> 64bit eflags) that reads as 1. This can be found in the AMD x86-64
> Programming manual vol 2 on page 65. Below is the code, I'm not sure how
> to put an ifdef around since I'm not sure if Intel's EMT64 with VMX cpus
> have the same rflag reserved (which if this check is correct they do)?
> This helps break x86-64 building domU domains.
It is a reserved bit on Intel as well. Look at:

VMCS_EFLAGS_RESERVED_1 and the IA-32 vol1 Fig 3-7.

Are you mixing up ctxt->user_regs.rflags and ctxt->flags in 
xc_linux_build.c?
        -Arun

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel