Re: New CPUID/MSR driver; virtualization hooks

[Zachary Amsden <zach@vmware.com>]

H. Peter Anvin wrote:
> It's not *quite* that easy.  The assembly code around this is pretty 
> extensive, because it has to stand on its head in order to present the 
> proper register image.
>   

Having just stood on my head for 55 breaths, might I suggest we 
implement a binary equivalent CPUID paravirt-ops wrapper; then the 
assembly code can just call CPUID and we can redefine it to call to a 
stub, which makes the pv-ops CPUID call, the puts the outputs back in 
the proper registers.

The VMI ROM CPUID is binary identical in register format with the native 
instruction, so it need not do a headstand.  For the others,

ENTRY(paravirt_raw_cpuid)
    pushl %edx
    pushl %ecx
    pushl %ebx
    pushl %eax
    mov %esp, %eax    /* pointer for eax in/out */
    leal 4(%esp), %edx /* pointer for ebx in/out */
    leal 8(%esp), %ecx /* pointer for ecx in/out */
    leal 12(%esp), %ebx /* pointer for edx in/out */
    pushl %ebx  /* arg 4 passed on stack */
    call *(paravirt_ops+pv_offset_CPUID)
    addl $4, %esp
    popl %eax
    popl %ebx
    popl %ecx
    popl %edx
    ret

Should do the right thing.  In any case, thanks for the heads up.

Zach