Re: [PATCH v2 01/15] KVM: Add member to struct kvm_gfn_range for target alias

[Paolo Bonzini]

On Thu, May 30, 2024 at 11:07 PM Rick Edgecombe
<rick.p.edgecombe@xxxxxxxxx> wrote:
> +       /* Unmmap the old attribute page. */

Unmap

> +       if (range->arg.attributes & KVM_MEMORY_ATTRIBUTE_PRIVATE)
> +               range->process = KVM_PROCESS_SHARED;
> +       else
> +               range->process = KVM_PROCESS_PRIVATE;
> +
>         return kvm_unmap_gfn_range(kvm, range);
>  }
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index c3c922bf077f..f92c8b605b03 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -260,11 +260,19 @@ union kvm_mmu_notifier_arg {
>         unsigned long attributes;
>  };
>
> +enum kvm_process {
> +       BUGGY_KVM_INVALIDATION          = 0,
> +       KVM_PROCESS_SHARED              = BIT(0),
> +       KVM_PROCESS_PRIVATE             = BIT(1),
> +       KVM_PROCESS_PRIVATE_AND_SHARED  = KVM_PROCESS_SHARED | KVM_PROCESS_PRIVATE,
> +};

Only KVM_PROCESS_SHARED and KVM_PROCESS_PRIVATE are needed.

> +       /*
> +        * If/when KVM supports more attributes beyond private .vs shared, this
> +        * _could_ set exclude_{private,shared} appropriately if the entire target

this could mask away KVM_PROCESS_{SHARED,PRIVATE} if the entire target...

Paolo

> +        * range already has the desired private vs. shared state (it's unclear
> +        * if that is a net win).  For now, KVM reaches this point if and only
> +        * if the private flag is being toggled, i.e. all mappings are in play.
> +        */
> +
>         for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) {
>                 slots = __kvm_memslots(kvm, i);
>
> @@ -2506,6 +2519,7 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
>         struct kvm_mmu_notifier_range pre_set_range = {
>                 .start = start,
>                 .end = end,
> +               .arg.attributes = attributes,
>                 .handler = kvm_pre_set_memory_attributes,
>                 .on_lock = kvm_mmu_invalidate_begin,
>                 .flush_on_ret = true,
> --
> 2.34.1
>