Re: [PATCH v10 2/9] KVM: Introduce per-page memory attributes

[Borislav Petkov]

On Fri, Dec 02, 2022 at 02:13:40PM +0800, Chao Peng wrote:
> diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
> index 1782c4555d94..7f0f5e9f2406 100644
> --- a/virt/kvm/kvm_main.c
> +++ b/virt/kvm/kvm_main.c
> @@ -1150,6 +1150,9 @@ static struct kvm *kvm_create_vm(unsigned long type, 
> const char *fdname)
>       spin_lock_init(&kvm->mn_invalidate_lock);
>       rcuwait_init(&kvm->mn_memslots_update_rcuwait);
>       xa_init(&kvm->vcpu_array);
> +#ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES
> +     xa_init(&kvm->mem_attr_array);
> +#endif

        if (IS_ENABLED(CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES))
                ...

would at least remove the ugly ifdeffery.

Or you could create wrapper functions for that xa_init() and
xa_destroy() and put the ifdeffery in there.

> @@ -2323,6 +2329,49 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm 
> *kvm,
>  }
>  #endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
>  
> +#ifdef CONFIG_HAVE_KVM_MEMORY_ATTRIBUTES
> +static u64 kvm_supported_mem_attributes(struct kvm *kvm)

I guess that function should have a verb in the name:

kvm_get_supported_mem_attributes()

> +static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
> +                                        struct kvm_memory_attributes *attrs)
> +{
> +     gfn_t start, end;
> +     unsigned long i;
> +     void *entry;
> +     u64 supported_attrs = kvm_supported_mem_attributes(kvm);
> +
> +     /* flags is currently not used. */
> +     if (attrs->flags)
> +             return -EINVAL;
> +     if (attrs->attributes & ~supported_attrs)
> +             return -EINVAL;
> +     if (attrs->size == 0 || attrs->address + attrs->size < attrs->address)
> +             return -EINVAL;
> +     if (!PAGE_ALIGNED(attrs->address) || !PAGE_ALIGNED(attrs->size))
> +             return -EINVAL;

Dunno, shouldn't those issue some sort of an error message so that the
caller knows where it failed? Or at least return different retvals which
signal what the problem is?

> +     start = attrs->address >> PAGE_SHIFT;
> +     end = (attrs->address + attrs->size - 1 + PAGE_SIZE) >> PAGE_SHIFT;
> +
> +     entry = attrs->attributes ? xa_mk_value(attrs->attributes) : NULL;
> +
> +     mutex_lock(&kvm->lock);
> +     for (i = start; i < end; i++)
> +             if (xa_err(xa_store(&kvm->mem_attr_array, i, entry,
> +                                 GFP_KERNEL_ACCOUNT)))
> +                     break;
> +     mutex_unlock(&kvm->lock);
> +
> +     attrs->address = i << PAGE_SHIFT;
> +     attrs->size = (end - i) << PAGE_SHIFT;
> +
> +     return 0;
> +}

-- 
Regards/Gruss,
    Boris.

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