linux-kernel - Re: [PATCH v5 19/19] KVM: selftests: Add test for KVM_SET_USER_MEMORY

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Message-ID: <20200206231127.GB24556@linux.intel.com>
Date:   Thu, 6 Feb 2020 15:11:27 -0800
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Paul Mackerras <paulus@...abs.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, Marc Zyngier <maz@...nel.org>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-mips@...r.kernel.org, kvm@...r.kernel.org,
        kvm-ppc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        Christoffer Dall <christoffer.dall@....com>,
        Philippe Mathieu-Daudé <f4bug@...at.org>
Subject: Re: [PATCH v5 19/19] KVM: selftests: Add test for
 KVM_SET_USER_MEMORY_REGION

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 <sean.j.christopherson@...el.com>
> 
> (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 <peterx@...hat.com>
> 
> -- 
> Peter Xu
>