Re: [PATCH v4 30/30] KVM: selftests: Add test to populate a VM with the max possible guest mem

[Sean Christopherson <seanjc@google.com>]

On Tue, Mar 08, 2022, Paolo Bonzini wrote:
> On 3/3/22 20:38, Paolo Bonzini wrote:
> > On x86, perform two passes with a MMU context reset between each pass to
> > coerce KVM into dropping all references to the MMU root, e.g. to emulate
> > a vCPU dropping the last reference.  Perform both passes and all
> > rendezvous on all architectures in the hope that arm64 and s390x can gain
> > similar shenanigans in the future.
> 
> Did you actually test aarch64 (not even asking about s390 :))?  For now
> let's only add it for x86.

Nope, don't you read my cover letters?  :-D

  The selftest at the end allows populating a guest with the max amount of
  memory allowed by the underlying architecture.  The most I've tested is
  ~64tb (MAXPHYADDR=46) as I don't have easy access to a system with
  MAXPHYADDR=52.  The selftest compiles on arm64 and s390x, but otherwise
  hasn't been tested outside of x86-64.  It will hopefully do something
  useful as is, but there's a non-zero chance it won't get past init with
  a high max memory.  Running on x86 without the TDP MMU is comically slow.


> > +			TEST_ASSERT(nr_vcpus, "#DE");
> 
> srsly? :)

LOL, yes.  IIRC I added that because I screwed up computing nr_vcpus and my
test did nothing useful :-)