linux-kernel - Re: [PATCH v2 8/8] DO NOT MERGE: Hack-a-test to verify gpc invalidation+refresh

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Message-ID: <68b3f18e156391e20aed8e10e974fdf8052b7f47.camel@infradead.org>
Date:   Wed, 27 Apr 2022 16:17:14 +0100
From:   David Woodhouse <dwmw2@...radead.org>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Mingwei Zhang <mizhang@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>
Subject: Re: [PATCH v2 8/8] DO NOT MERGE: Hack-a-test to verify gpc
 invalidation+refresh

On Wed, 2022-04-27 at 01:40 +0000, Sean Christopherson wrote:
> Add a VM-wide gfn=>pfn cache and a fake MSR to let userspace control the
> cache.  On writes, reflect the value of the MSR into the backing page of
> a gfn=>pfn cache so that userspace can detect if a value was written to
> the wrong page, i.e. to a stale mapping.
> 
> Spin up 16 vCPUs (arbitrary) to use/refresh the cache, and another thread
> to trigger mmu_notifier events and memslot updates.

Do you need the MSR hack? Can't you exercise this using Xen interrupt
delivery or runstate information and the same kind of thread setup?

Thanks for working on this!

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