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

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