Subject: Re: [PATCH v5 19/19] KVM: selftests: Add test for KVM_SET_USER_MEMORY_REGION

From: Sean Christopherson <[email-masked]>
Date: Thu, 6 Feb 2020 15:11:27 -0800

On Thu, Feb 06, 2020 at 05:30:01PM -0500, Peter Xu wrote:
> On Tue, Jan 21, 2020 at 02:31:57PM -0800, Sean Christopherson wrote:
> > Add a KVM selftest to test moving the base gfn of a userspace memory
> > region.  Although the basic concept of moving memory regions is not x86
> > specific, the assumptions regarding large pages and MMIO shenanigans
> > used to verify the correctness make this x86_64 only for the time being.
> > 
> > Signed-off-by: Sean Christopherson <[email-masked]>
> 
> (I'm a bit curious why write 2 first before 1...)

To verify KVM actually relocated the memslot and didn't leave anything in
the TLB.  If "2" isn't written, KVM could completely botch the MOVE but the
guest_code() would still signal pass because it would eventually see the
0-> transitions.

> Reviewed-by: Peter Xu <[email-masked]>
> 
> -- 
> Peter Xu
> 

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