Re: [PATCH 3/4] test: Add mode-switch test for nested svm

["Roedel, Joerg" <Joerg.Roedel@amd.com>]

On Mon, Aug 02, 2010 at 10:24:43AM -0400, Avi Kivity wrote:
>   On 08/02/2010 05:11 PM, Roedel, Joerg wrote:

> > This is testing the failure case without the nested-svm efer patch I
> > submitted last week. The sequence above (which switches from long mode
> > to real mode and back to long mode) fails without this patch.
> 
> A direct test would be to
> 
>    mov $MSR_EFER, %ecx
>    rdmsr
>    xor $EFER_NX, %eax
>    wrmsr
> 
> and see that L1 EFER was updated.
> 
> I don't object to the more complicated test, but in general prefer 
> simpler, direct tests so that when they fail we know exactly why.

True, smaller tests are generally better. But I think its good to also
test that the whole sequence works. I can add a seperate test for the
efer bug if you want.
It gets more tricky to test cr0 or cr4 writes because this will require
to put the nested guest into real-mode or protected-mode directly.

	Joerg

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