linux-kernel - Re: [PATCH 2/6] KVM: selftests: Stash the host page size in a global in the guest

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Message-ID: <aNq6qWVEBLkWhWFc@google.com>
Date: Mon, 29 Sep 2025 09:58:17 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Ackerley Tng <ackerleytng@...gle.com>
Cc: Paolo Bonzini <pbonzini@...hat.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, 
	Janosch Frank <frankja@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, David Hildenbrand <david@...hat.com>, 
	Fuad Tabba <tabba@...gle.com>
Subject: Re: [PATCH 2/6] KVM: selftests: Stash the host page size in a global
 in the guest_memfd test

On Mon, Sep 29, 2025, Ackerley Tng wrote:
> Sean Christopherson <seanjc@...gle.com> writes:
> 
> > Use a global variable to track the host page size in the guest_memfd test
> > so that the information doesn't need to be constantly passed around.  The
> > state is purely a reflection of the underlying system, i.e. can't be set
> > by the test and is constant for a given invocation of the test, and thus
> > explicitly passing the host page size to individual testcases adds no
> > value, e.g. doesn't allow testing different combinations.
> >
> 
> I was going to pass in page_size to each of these test cases to test
> HugeTLB support, that's how page_size crept into the parameters of these
> functions.
> 
> Could we do a getpagesize() within the gmem_test() macro that you
> introduced instead?

We could, and I actually had it that way to start.  But I found that burying the
effective setting of page_size made it harder to see that it's a runtime constant,
versus something that can be configured by the test.