linux-kernel - Re: [V1 PATCH 2/5] selftests: kvm: Introduce kvm_arch

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Date:   Fri, 9 Sep 2022 09:01:25 +0200
From:   Andrew Jones <andrew.jones@...ux.dev>
To:     David Matlack <dmatlack@...gle.com>
Cc:     Vishal Annapurve <vannapurve@...gle.com>, x86 <x86@...nel.org>,
        kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-kselftest@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>, shuah <shuah@...nel.org>,
        Ben Gardon <bgardon@...gle.com>,
        Sean Christopherson <seanjc@...gle.com>, oupton@...gle.com,
        peterx@...hat.com, Vitaly Kuznetsov <vkuznets@...hat.com>,
        drjones@...hat.com
Subject: Re: [V1 PATCH 2/5] selftests: kvm: Introduce kvm_arch_main and
 helpers

On Thu, Sep 08, 2022 at 02:21:52PM -0700, David Matlack wrote:
> On Tue, Sep 06, 2022 at 03:46:20PM -0700, Vishal Annapurve wrote:
> > On Mon, Sep 5, 2022 at 12:46 AM Andrew Jones <andrew.jones@...ux.dev> wrote:
> > >
> > > On Sat, Sep 03, 2022 at 01:28:46AM +0000, Vishal Annapurve wrote:
> > > > Introduce following APIs:
> > > > 1) kvm_arch_main : to be called at the startup of each test.
> > >
> > > With this, AArch64 can move the content of its constructor,
> > > init_guest_modes(), into kvm_arch_main(). Or, instead of the
> > >
> > >  main()
> > >  {
> > >     /* common main stuff */
> > >     kvm_arch_main();
> > >     __main();
> > >  }
> > >
> > > approach we could have each arch provide a constructor
> > >
> > >  arch_init()
> > >  {
> > >     common_pre_main_stuff();
> > >     /* arch specific pre-main stuff */
> > >  }
> > >
> > > I personally prefer the latter.
> > >
> > 
> > I agree with your suggestion of using constructors here. This will
> > help avoid changes in all the selftests.
> > Maybe I can add a common constructor that can invoke arch specific
> > init. I will add this change in the next series.
> 
> In case anyone else is confused like me: "constructor" refers to
> __attribute__ ((constructor)), which causes the function to run before
> main().
> 
> I have a slight preference for having as few constructors as possible,
> since they are somewhat subtle. So how about one constructor for all
> selftests, e.g.:
> 
> void __attribute__ ((constructor)) kvm_selftest_init(void)
> {
>         /* Tell stdout not to buffer its content. */
>         setbuf(stdout, NULL);
> 
>         kvm_selftest_arch_init();
> }
> 
> Per-arch:
> 
> void kvm_selftest_arch_init(void)
> {
>         /* arch-specific pre-main stuff */
> }

WFM and I think that's what Vishal was suggesting as well.

Thanks,
drew