linux-kernel - Re: [V2 PATCH 3/8] KVM: selftests: Add arch specific post vm load setup

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Message-ID: <CAGtprH-YuA=b-oJDZnvZ5u1EfNPuwUvrbYE0fU2L2KHzu5Af_g@mail.gmail.com>
Date:   Mon, 3 Oct 2022 17:02:27 -0700
From:   Vishal Annapurve <vannapurve@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     David Matlack <dmatlack@...gle.com>, x86 <x86@...nel.org>,
        kvm list <kvm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linuxkselftest <linux-kselftest@...r.kernel.org>,
        Paolo Bonzini <pbonzini@...hat.com>, shuah <shuah@...nel.org>,
        Ben Gardon <bgardon@...gle.com>,
        Oliver Upton <oupton@...gle.com>, Peter Xu <peterx@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [V2 PATCH 3/8] KVM: selftests: Add arch specific post vm load setup

On Mon, Oct 3, 2022 at 8:42 AM Sean Christopherson <seanjc@...gle.com> wrote:
>
> On Mon, Sep 26, 2022, Vishal Annapurve wrote:
> > On Wed, Sep 21, 2022 at 1:54 PM David Matlack <dmatlack@...gle.com> wrote:
> > >
> > > On Thu, Sep 15, 2022 at 12:04:43AM +0000, Vishal Annapurve wrote:
> > > > diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
> > > > index 98edbbda9f97..73cfee3ebd76 100644
> > > > --- a/tools/testing/selftests/kvm/include/kvm_util_base.h
> > > > +++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
> > > > @@ -839,4 +839,8 @@ static inline int __vm_disable_nx_huge_pages(struct kvm_vm *vm)
> > > >   */
> > > >  void kvm_selftest_arch_init(void);
> > > >
> > > > +/*
> > > > + * API to execute architecture specific setup after loading the vm elf.
> > >
> > > It's not a "vm elf" per-se, it's "loading the elf into the VM". How
> > > about:
> > >
> > > /*
> > >  * API to execute arch-specific logic after loading the selftest ELF image
> > >  * into the VM.
> > >  */
> > >
> >
> > Ack. Will update this in the next series.
>
> Even better, call it from __vm_create() and name it something like
> kvm_arch_vm_post_create().  Like David said, while the hook has a dependency on
> being called after loading the ELF image, the action that arch code is expected
> to take doesn't have anything to do with loading the ELF image.
>
> And then instead of introducing an arch hook with no implementation, the patch that
> adds the hook can instead use it to replace the x86-64 #ifdef in __vm_create().
>

Today upstream kernel selftests don't have scenarios where
kvm_vm_elf_load can get called directly outside ___vm_create but there
are selftests that are up for review [1], [2] that may call
kvm_vm_elf_load directly. Above suggestion will not work in this
scenario, is it suitable to assume that all the callers of
kvm_vm_elf_load will eventually execute kvm_arch_vm_post_create?

[1] https://lore.kernel.org/lkml/20220810152033.946942-12-pgonda@google.com/
[2] https://lore.kernel.org/lkml/20220819174659.2427983-1-vannapurve@google.com/T/#u

> diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
> index dafe4471a6c7..593dfadb662e 100644
> --- a/tools/testing/selftests/kvm/lib/kvm_util.c
> +++ b/tools/testing/selftests/kvm/lib/kvm_util.c
> @@ -298,9 +298,8 @@ struct kvm_vm *__vm_create(enum vm_guest_mode mode, uint32_t nr_runnable_vcpus,
>
>         kvm_vm_elf_load(vm, program_invocation_name);
>
> -#ifdef __x86_64__
> -       vm_create_irqchip(vm);
> -#endif
> +       kvm_arch_vm_post_create(vm);
> +
>         return vm;
>  }
>
>