[v11] Direct Map Removal Support for guest_memfd

[PATCH v11 03/16] mm/secretmem: make use of folio_{zap,restore}_direct_map

Posted by Kalyazin, Nikita 2 weeks, 1 day ago

From: Nikita Kalyazin <kalyazin@amazon.com>

Signed-off-by: Nikita Kalyazin <kalyazin@amazon.com>
---
 mm/secretmem.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/mm/secretmem.c b/mm/secretmem.c
index fd29b33c6764..27b176af8fc4 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -53,7 +53,6 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
 	struct inode *inode = file_inode(vmf->vma->vm_file);
 	pgoff_t offset = vmf->pgoff;
 	gfp_t gfp = vmf->gfp_mask;
-	unsigned long addr;
 	struct folio *folio;
 	vm_fault_t ret;
 	int err;
@@ -72,7 +71,7 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
 			goto out;
 		}
 
-		err = set_direct_map_invalid_noflush(folio_address(folio));
+		err = folio_zap_direct_map(folio);
 		if (err) {
 			folio_put(folio);
 			ret = vmf_error(err);
@@ -87,7 +86,7 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
 			 * already happened when we marked the page invalid
 			 * which guarantees that this call won't fail
 			 */
-			set_direct_map_default_noflush(folio_address(folio));
+			folio_restore_direct_map(folio);
 			folio_put(folio);
 			if (err == -EEXIST)
 				goto retry;
@@ -95,9 +94,6 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
 			ret = vmf_error(err);
 			goto out;
 		}
-
-		addr = (unsigned long)folio_address(folio);
-		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
 	}
 
 	vmf->page = folio_file_page(folio, vmf->pgoff);
-- 
2.50.1

Re: [PATCH v11 03/16] mm/secretmem: make use of folio_{zap,restore}_direct_map

Posted by Ackerley Tng 1 week, 2 days ago

"Kalyazin, Nikita" <kalyazin@amazon.co.uk> writes:

> From: Nikita Kalyazin <kalyazin@amazon.com>
>
> Signed-off-by: Nikita Kalyazin <kalyazin@amazon.com>
> ---
>  mm/secretmem.c | 8 ++------
>  1 file changed, 2 insertions(+), 6 deletions(-)
>
> diff --git a/mm/secretmem.c b/mm/secretmem.c
> index fd29b33c6764..27b176af8fc4 100644
> --- a/mm/secretmem.c
> +++ b/mm/secretmem.c
> @@ -53,7 +53,6 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
>  	struct inode *inode = file_inode(vmf->vma->vm_file);
>  	pgoff_t offset = vmf->pgoff;
>  	gfp_t gfp = vmf->gfp_mask;
> -	unsigned long addr;
>  	struct folio *folio;
>  	vm_fault_t ret;
>  	int err;
> @@ -72,7 +71,7 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
>  			goto out;
>  		}
>
> -		err = set_direct_map_invalid_noflush(folio_address(folio));
> +		err = folio_zap_direct_map(folio);
>  		if (err) {
>  			folio_put(folio);
>  			ret = vmf_error(err);
> @@ -87,7 +86,7 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
>  			 * already happened when we marked the page invalid
>  			 * which guarantees that this call won't fail
>  			 */
> -			set_direct_map_default_noflush(folio_address(folio));
> +			folio_restore_direct_map(folio);
>  			folio_put(folio);
>  			if (err == -EEXIST)
>  				goto retry;
> @@ -95,9 +94,6 @@ static vm_fault_t secretmem_fault(struct vm_fault *vmf)
>  			ret = vmf_error(err);
>  			goto out;
>  		}
> -
> -		addr = (unsigned long)folio_address(folio);
> -		flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
>  	}
>
>  	vmf->page = folio_file_page(folio, vmf->pgoff);
> --
> 2.50.1

Reviewed-by: Ackerley Tng <ackerleytng@google.com>

Re: [PATCH v11 03/16] mm/secretmem: make use of folio_{zap,restore}_direct_map

Posted by David Hildenbrand (Arm) 1 week, 2 days ago

On 3/17/26 15:11, Kalyazin, Nikita wrote:
> From: Nikita Kalyazin <kalyazin@amazon.com>
> 

Describe your change :)

Ans also worth mentioning that we now flush the TLB even though
filemap_add_folio() failed -- which shouldn't matter in practice I guess.

With that

Acked-by: David Hildenbrand (Arm) <david@kernel.org>

-- 
Cheers,

David