linux-kernel - Re: [PATCH v3 11/13] KVM: selftests / xen: map shared

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Date:   Mon, 18 Sep 2023 17:16:08 +0100
From:   David Woodhouse <dwmw2@...radead.org>
To:     Paul Durrant <paul@....org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Paul Durrant <pdurrant@...zon.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH v3 11/13] KVM: selftests / xen: map shared_info using
 HVA rather than GFN

On Mon, 2023-09-18 at 14:41 +0000, Paul Durrant wrote:
> 
>         for (;;) {
> -               __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_activate);
> -               __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_deactivate);
> +               __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_activate_gfn);
>                 pthread_testcancel();
> +               __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_deactivate_gfn);
> +
> +               if (xen_caps & KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA) {
> +                       __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_activate_hva);
> +                       pthread_testcancel();
> +                       __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_deactivate_hva);
> +               }
>         }
>  


So now the loop starts by activating it in GFN mode even if it was
already activated in HVA mode. Is that something we should even allow?
I suppose it doesn't hurt.

And it *may* leave it activated in either HVA or GFN mode.

Are both deactivate modes equivalent? I think they are, aren't they?

So it could be...

 for (;;) {
   __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_deactivate);
   __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_activate);

    if (xen_caps & KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA) {
        __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_deactivate_hva);
        __vm_ioctl(vm, KVM_XEN_HVM_SET_ATTR, &cache_activate_hva);
    }
    pthread_testcancel();
 }

But that's just nitpicking, I suppose.

Reviewed-by: David Woodhouse <dwmw@...zon.co.uk>

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