Re: [Xen-devel] [PATCH 1/6] x86/vmx: Simplfy the default cases in vmx_msr_{read, write}_intercept()

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Feb 27, 2018 at 12:43:21PM +0000, Roger Pau Monné wrote:
> On Mon, Feb 26, 2018 at 05:35:14PM +0000, Andrew Cooper wrote:
> > The default case of vmx_msr_write_intercept() in particular is very tangled.
> > 
> > First of all, fold long_mode_do_msr_{read,write}() into their callers.  
> > These
> > functions were split out in the past because of the 32bit build of Xen, but 
> > it
> > is unclear why the cases weren't simply #ifdef'd in place.
> > 
> > Next, invert the vmx_write_guest_msr()/is_last_branch_msr() logic to break 
> > if
> > the condition is satisfied, rather than nesting if it wasn't.  This allows 
> > the
> > wrmsr_hypervisor_regs() call to be un-nested with respect to the other 
> > default
> > logic.
> > 
> > No practical difference from a guests point of view.
> 
> I think there's a difference from guest PoV now, guest wrmsr of
> GS/FS/LSTAR/CSTAR with non-canonical addresses will get a #GP.

Forget about this, I've just realized this is completely wrong.

And I've also figured out my question to CSTAR, so:

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

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