[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

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?


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.