[PATCH 02/20] KVM: arm64: Add support for creating kernel-agnostic stage-1 page tables

[Quentin Perret]

Hey Will,

On Thursday 30 Jul 2020 at 16:33:48 (+0100), Will Deacon wrote:
> +void *kvm_pgtable_hyp_alloc_cookie(u32 va_bits)
> +{
> +	struct kvm_pgtable *pgt = kzalloc(sizeof(*pgt), GFP_KERNEL);
> +
> +	if (!pgt)
> +		return NULL;
> +
> +	pgt->ia_bits = va_bits;
> +	pgt->start_level = kvm_start_level(va_bits);
> +
> +	pgt->pgd = (kvm_pte_t *)get_zeroed_page(GFP_KERNEL);
> +	if (!pgt->pgd) {
> +		kfree(pgt);
> +		pgt = NULL;
> +	}
> +
> +	return pgt;
> +}
> +
> +static int hyp_free_walker(u64 addr, u64 end, u32 level, kvm_pte_t *ptep,
> +			   enum kvm_pgtable_walk_flags flag, void * const arg)
> +{
> +	free_page((unsigned long)kvm_pte_follow(*ptep));
> +	return 0;
> +}
> +
> +void kvm_pgtable_hyp_free_cookie(void *cookie)
> +{
> +	size_t pgd_sz;
> +	struct kvm_pgtable *pgt = cookie;
> +	struct kvm_pgtable_walker walker = {
> +		.cb	= hyp_free_walker,
> +		.flags	= KVM_PGTABLE_WALK_TABLE_POST,
> +	};
> +
> +	if (kvm_pgtable_walk(cookie, 0, BIT(pgt->ia_bits), &walker))
> +		kvm_err("Failed to free page-table pages\n");
> +
> +	pgd_sz = kvm_pgd_pages(pgt) * PAGE_SIZE;
> +	free_pages_exact(pgt->pgd, pgd_sz);

Given that the pgd is unconditionally a single page for the stage 1 case
(as per kvm_pgtable_hyp_alloc_cookie() above), should we simplify this
to a simple free_page()? Or did you want to factorize this with the
stage 2 free path?

> +	kfree(pgt);
> +}

Cheers,
Quentin