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

From: Sean Christopherson
Date: Wed Apr 27 2022 - 16:23:42 EST

On Wed, Apr 27, 2022, David Woodhouse wrote:
> 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?

Yeah, I asumme it's possible, and medium/long term I definitely want to have a
proper test. I went the hack route to get something that could hammer a cache
with minimal chance of a test bug. I only have a rough idea of what the Xen stuff