On Thu, Apr 04, 2024, Paolo Bonzini wrote:
> +long kvm_gmem_populate(struct kvm *kvm, gfn_t gfn, void __user *src, long npages,
> + int (*post_populate)(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
> + void __user *src, int order, void *opaque),
Add a typedef for callback? If only to make this prototype readable.
> +long kvm_gmem_populate(struct kvm *kvm, gfn_t gfn, void __user *src, long npages,
> + int (*post_populate)(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
> + void __user *src, int order, void *opaque),
> + void *opaque)
> +{
> + struct file *file;
> + struct kvm_memory_slot *slot;
> +
> + int ret = 0, max_order;
> + long i;
> +
> + lockdep_assert_held(&kvm->slots_lock);
> + if (npages < 0)
> + return -EINVAL;
> +
> + slot = gfn_to_memslot(kvm, gfn);
> + if (!kvm_slot_can_be_private(slot))
> + return -EINVAL;
> +
> + file = kvm_gmem_get_file(slot);
> + if (!file)
> + return -EFAULT;
> +
> + filemap_invalidate_lock(file->f_mapping);
> +
> + npages = min_t(ulong, slot->npages - (gfn - slot->base_gfn), npages);
> + for (i = 0; i < npages; i += (1 << max_order)) {
> + gfn_t this_gfn = gfn + i;
KVM usually does something like "start_gfn" or "base_gfn", and then uses "gfn"
for the one gfn that's being processed. And IMO that's much better because the
propotype for kvm_gmem_populate() does not make it obvious that @gfn is the base
of a range, not a singular gfn to process.
> + kvm_pfn_t pfn;
> +
> + ret = __kvm_gmem_get_pfn(file, slot, this_gfn, &pfn, &max_order, false);
> + if (ret)
> + break;
> +
> + if (!IS_ALIGNED(this_gfn, (1 << max_order)) ||
> + (npages - i) < (1 << max_order))
> + max_order = 0;
> +
> + if (post_populate) {
Is there any use for this without @post_populate? I.e. why make this optional?
> + void __user *p = src ? src + i * PAGE_SIZE : NULL;
Eh, I would vote to either define "p" at the top of the loop.
> + ret = post_populate(kvm, this_gfn, pfn, p, max_order, opaque);
> + }
> +
> + put_page(pfn_to_page(pfn));
> + if (ret) {
> + /*
> + * Punch a hole so that FGP_CREAT_ONLY can succeed
> + * again.
> + */
> + kvm_gmem_undo_get_pfn(file, slot, this_gfn, max_order);
> + break;
> + }
> + }
> +
> + filemap_invalidate_unlock(file->f_mapping);
> +
> + fput(file);
> + return ret && !i ? ret : i;
> +}
> +EXPORT_SYMBOL_GPL(kvm_gmem_populate);
> --
> 2.43.0
>
>
