Re: [PATCH v3 02/12] KVM: arm64: Rename free_unlinked to free_removed

[Oliver Upton <oliver.upton@linux.dev>]

On Wed, Feb 15, 2023 at 05:40:36PM +0000, Ricardo Koller wrote:
> Make it clearer that the "free_removed" functions refer to tables that
> have never been part of the paging structure: they are "unlinked".

the page table passed to ->free_removed_table() was definitely part of a
paging structure before. Maybe:

  A subsequent change to KVM will add support for building page tables
  that are not part of an active paging structure. The existing
  'removed_table' terminology is quite clunky when applied in this
  context.

  Normalize on referring to tables outside of an active paging structure
  as 'unlinked'. No functional change intended.

> No functional change intended.
> 
> Signed-off-by: Ricardo Koller <ricarkol@google.com>

besides the changelog nit:

Reviewed-by: Oliver Upton <oliver.upton@linux.dev>

--
Thanks,
Oliver

> ---
>  arch/arm64/include/asm/kvm_pgtable.h  |  8 ++++----
>  arch/arm64/kvm/hyp/nvhe/mem_protect.c |  6 +++---
>  arch/arm64/kvm/hyp/pgtable.c          |  6 +++---
>  arch/arm64/kvm/mmu.c                  | 10 +++++-----
>  4 files changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_pgtable.h b/arch/arm64/include/asm/kvm_pgtable.h
> index 3339192a97a9..7c45082e6c23 100644
> --- a/arch/arm64/include/asm/kvm_pgtable.h
> +++ b/arch/arm64/include/asm/kvm_pgtable.h
> @@ -99,7 +99,7 @@ static inline bool kvm_level_supports_block_mapping(u32 level)
>   *				allocation is physically contiguous.
>   * @free_pages_exact:		Free an exact number of memory pages previously
>   *				allocated by zalloc_pages_exact.
> - * @free_removed_table:		Free a removed paging structure by unlinking and
> + * @free_unlinked_table:	Free an unlinked paging structure by unlinking and
>   *				dropping references.
>   * @get_page:			Increment the refcount on a page.
>   * @put_page:			Decrement the refcount on a page. When the
> @@ -119,7 +119,7 @@ struct kvm_pgtable_mm_ops {
>  	void*		(*zalloc_page)(void *arg);
>  	void*		(*zalloc_pages_exact)(size_t size);
>  	void		(*free_pages_exact)(void *addr, size_t size);
> -	void		(*free_removed_table)(void *addr, u32 level);
> +	void		(*free_unlinked_table)(void *addr, u32 level);
>  	void		(*get_page)(void *addr);
>  	void		(*put_page)(void *addr);
>  	int		(*page_count)(void *addr);
> @@ -450,7 +450,7 @@ int __kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm_s2_mmu *mmu,
>  void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);
>  
>  /**
> - * kvm_pgtable_stage2_free_removed() - Free a removed stage-2 paging structure.
> + * kvm_pgtable_stage2_free_unlinked() - Free un unlinked stage-2 paging structure.
>   * @mm_ops:	Memory management callbacks.
>   * @pgtable:	Unlinked stage-2 paging structure to be freed.
>   * @level:	Level of the stage-2 paging structure to be freed.
> @@ -458,7 +458,7 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt);
>   * The page-table is assumed to be unreachable by any hardware walkers prior to
>   * freeing and therefore no TLB invalidation is performed.
>   */
> -void kvm_pgtable_stage2_free_removed(struct kvm_pgtable_mm_ops *mm_ops, void *pgtable, u32 level);
> +void kvm_pgtable_stage2_free_unlinked(struct kvm_pgtable_mm_ops *mm_ops, void *pgtable, u32 level);
>  
>  /**
>   * kvm_pgtable_stage2_map() - Install a mapping in a guest stage-2 page-table.
> diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> index 552653fa18be..b030170d803b 100644
> --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c
> @@ -91,9 +91,9 @@ static void host_s2_put_page(void *addr)
>  	hyp_put_page(&host_s2_pool, addr);
>  }
>  
> -static void host_s2_free_removed_table(void *addr, u32 level)
> +static void host_s2_free_unlinked_table(void *addr, u32 level)
>  {
> -	kvm_pgtable_stage2_free_removed(&host_mmu.mm_ops, addr, level);
> +	kvm_pgtable_stage2_free_unlinked(&host_mmu.mm_ops, addr, level);
>  }
>  
>  static int prepare_s2_pool(void *pgt_pool_base)
> @@ -110,7 +110,7 @@ static int prepare_s2_pool(void *pgt_pool_base)
>  	host_mmu.mm_ops = (struct kvm_pgtable_mm_ops) {
>  		.zalloc_pages_exact = host_s2_zalloc_pages_exact,
>  		.zalloc_page = host_s2_zalloc_page,
> -		.free_removed_table = host_s2_free_removed_table,
> +		.free_unlinked_table = host_s2_free_unlinked_table,
>  		.phys_to_virt = hyp_phys_to_virt,
>  		.virt_to_phys = hyp_virt_to_phys,
>  		.page_count = hyp_page_count,
> diff --git a/arch/arm64/kvm/hyp/pgtable.c b/arch/arm64/kvm/hyp/pgtable.c
> index e093e222daf3..0a5ef9288371 100644
> --- a/arch/arm64/kvm/hyp/pgtable.c
> +++ b/arch/arm64/kvm/hyp/pgtable.c
> @@ -841,7 +841,7 @@ static int stage2_map_walk_table_pre(const struct kvm_pgtable_visit_ctx *ctx,
>  	if (ret)
>  		return ret;
>  
> -	mm_ops->free_removed_table(childp, ctx->level);
> +	mm_ops->free_unlinked_table(childp, ctx->level);
>  	return 0;
>  }
>  
> @@ -886,7 +886,7 @@ static int stage2_map_walk_leaf(const struct kvm_pgtable_visit_ctx *ctx,
>   * The TABLE_PRE callback runs for table entries on the way down, looking
>   * for table entries which we could conceivably replace with a block entry
>   * for this mapping. If it finds one it replaces the entry and calls
> - * kvm_pgtable_mm_ops::free_removed_table() to tear down the detached table.
> + * kvm_pgtable_mm_ops::free_unlinked_table() to tear down the detached table.
>   *
>   * Otherwise, the LEAF callback performs the mapping at the existing leaves
>   * instead.
> @@ -1250,7 +1250,7 @@ void kvm_pgtable_stage2_destroy(struct kvm_pgtable *pgt)
>  	pgt->pgd = NULL;
>  }
>  
> -void kvm_pgtable_stage2_free_removed(struct kvm_pgtable_mm_ops *mm_ops, void *pgtable, u32 level)
> +void kvm_pgtable_stage2_free_unlinked(struct kvm_pgtable_mm_ops *mm_ops, void *pgtable, u32 level)
>  {
>  	kvm_pteref_t ptep = (kvm_pteref_t)pgtable;
>  	struct kvm_pgtable_walker walker = {
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index a3ee3b605c9b..9bd3c2cfb476 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -130,21 +130,21 @@ static void kvm_s2_free_pages_exact(void *virt, size_t size)
>  
>  static struct kvm_pgtable_mm_ops kvm_s2_mm_ops;
>  
> -static void stage2_free_removed_table_rcu_cb(struct rcu_head *head)
> +static void stage2_free_unlinked_table_rcu_cb(struct rcu_head *head)
>  {
>  	struct page *page = container_of(head, struct page, rcu_head);
>  	void *pgtable = page_to_virt(page);
>  	u32 level = page_private(page);
>  
> -	kvm_pgtable_stage2_free_removed(&kvm_s2_mm_ops, pgtable, level);
> +	kvm_pgtable_stage2_free_unlinked(&kvm_s2_mm_ops, pgtable, level);
>  }
>  
> -static void stage2_free_removed_table(void *addr, u32 level)
> +static void stage2_free_unlinked_table(void *addr, u32 level)
>  {
>  	struct page *page = virt_to_page(addr);
>  
>  	set_page_private(page, (unsigned long)level);
> -	call_rcu(&page->rcu_head, stage2_free_removed_table_rcu_cb);
> +	call_rcu(&page->rcu_head, stage2_free_unlinked_table_rcu_cb);
>  }
>  
>  static void kvm_host_get_page(void *addr)
> @@ -681,7 +681,7 @@ static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = {
>  	.zalloc_page		= stage2_memcache_zalloc_page,
>  	.zalloc_pages_exact	= kvm_s2_zalloc_pages_exact,
>  	.free_pages_exact	= kvm_s2_free_pages_exact,
> -	.free_removed_table	= stage2_free_removed_table,
> +	.free_unlinked_table	= stage2_free_unlinked_table,
>  	.get_page		= kvm_host_get_page,
>  	.put_page		= kvm_s2_put_page,
>  	.page_count		= kvm_host_page_count,
> -- 
> 2.39.1.637.g21b0678d19-goog
> 
> 

-- 
Thanks,
Oliver