VMX check in /xen/arch/x86/domain.c is invalid on x86-64 (at least AMD)

VMX check in /xen/arch/x86/domain.c is invalid on x86-64 (at least AMD)

[Jerone Young]

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.

-- 
Jerone Young
IBM Linux Technology Center
jyoung5@us.ibm.com
512-838-1157 (T/L: 678-1157)

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

[Arun Sharma]

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

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

[Jerone Young]

Yes I am actually. Sorry guy. I got that one screwed up in my head.
Pressed the send button too quickly. Thanks for the respsonses though.

On 5/12/05, Arun Sharma <arun.sharma@intel.com> wrote:
> 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
> 
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