linux-kernel - Re: [PATCH 00/13] KVM: x86: Add a cap to disable NX hugepages on a VM

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Date:   Fri, 11 Mar 2022 02:19:32 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Ben Gardon <bgardon@...gle.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Peter Xu <peterx@...hat.com>,
        David Matlack <dmatlack@...gle.com>,
        Jim Mattson <jmattson@...gle.com>,
        David Dunn <daviddunn@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Junaid Shahid <junaids@...gle.com>
Subject: Re: [PATCH 00/13] KVM: x86: Add a cap to disable NX hugepages on a VM

On Thu, Mar 10, 2022, Ben Gardon wrote:
> Those patches are a lot of churn, but at least to me, they make the
> code much more readable. Currently there are many functions which just
> pass along 0 for the memslot, and often have multiple other numerical
> arguments, which makes it hard to understand what the function is
> doing.

Yeah, my solution for that was to rip out all the params.  E.g. the most used
function I ended up with is

  static inline struct kvm_vm *vm_create_with_one_vcpu(struct kvm_vcpu **vcpu,
						     void *guest_code)
  {
	return __vm_create_with_one_vcpu(vcpu, 0, guest_code);
  }

and then the usage is

	vm = vm_create_with_one_vcpu(&vcpu, guest_main);

	supp_cpuid = kvm_get_supported_cpuid();
	cpuid2 = vcpu_get_cpuid(vcpu);

My overarching complaint with the selftests is that they make the hard things hard,
and the easy things harder.  If a test wants to be backed by hugepages, it shouldn't
have to manually specify a memslot.

Let me post my selftests rework as RFC (_very_ RFC at this point).  I was hoping to
do more than compile test before posting anything, but it's going to be multiple
weeks before I'll get back to it.  Hopefully it'll start a discussion on actually
rewriting the framework so that writing new tests is less painful, and so that every
new thing that comes along doesn't require poking at 50 different tests.