Re: [PATCH] mm: Track page table modifications in __apply_to_page_range() construction

[Greg KH]

On Fri, Aug 21, 2020 at 12:09:02PM +0200, Joerg Roedel wrote:
> The __apply_to_page_range() function is also used to change and/or
> allocate page-table pages in the vmalloc area of the address space.
> Make sure these changes get synchronized to other page-tables in the
> system by calling arch_sync_kernel_mappings() when necessary.
> 
> Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
> ---
> (Only compile tested on x86-64 so far)
> 
>  mm/memory.c | 32 +++++++++++++++++++++-----------
>  1 file changed, 21 insertions(+), 11 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 3a7779d9891d..fd845991f14a 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -83,6 +83,7 @@
>  #include <asm/tlb.h>
>  #include <asm/tlbflush.h>
>  
> +#include "pgalloc-track.h"
>  #include "internal.h"
>  
>  #if defined(LAST_CPUPID_NOT_IN_PAGE_FLAGS) && !defined(CONFIG_COMPILE_TEST)
> @@ -2206,7 +2207,8 @@ EXPORT_SYMBOL(vm_iomap_memory);
>  
>  static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
>  				     unsigned long addr, unsigned long end,
> -				     pte_fn_t fn, void *data, bool create)
> +				     pte_fn_t fn, void *data, bool create,
> +				     pgtbl_mod_mask *mask)
>  {
>  	pte_t *pte;
>  	int err = 0;
> @@ -2235,6 +2237,7 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
>  				break;
>  		}
>  	} while (addr += PAGE_SIZE, addr != end);
> +	*mask |= PGTBL_PTE_MODIFIED;
>  
>  	arch_leave_lazy_mmu_mode();
>  
> @@ -2245,7 +2248,8 @@ static int apply_to_pte_range(struct mm_struct *mm, pmd_t *pmd,
>  
>  static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
>  				     unsigned long addr, unsigned long end,
> -				     pte_fn_t fn, void *data, bool create)
> +				     pte_fn_t fn, void *data, bool create,
> +				     pgtbl_mod_mask *mask)
>  {
>  	pmd_t *pmd;
>  	unsigned long next;
> @@ -2254,7 +2258,7 @@ static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
>  	BUG_ON(pud_huge(*pud));
>  
>  	if (create) {
> -		pmd = pmd_alloc(mm, pud, addr);
> +		pmd = pmd_alloc_track(mm, pud, addr, mask);
>  		if (!pmd)
>  			return -ENOMEM;
>  	} else {
> @@ -2264,7 +2268,7 @@ static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
>  		next = pmd_addr_end(addr, end);
>  		if (create || !pmd_none_or_clear_bad(pmd)) {
>  			err = apply_to_pte_range(mm, pmd, addr, next, fn, data,
> -						 create);
> +						 create, mask);
>  			if (err)
>  				break;
>  		}
> @@ -2274,14 +2278,15 @@ static int apply_to_pmd_range(struct mm_struct *mm, pud_t *pud,
>  
>  static int apply_to_pud_range(struct mm_struct *mm, p4d_t *p4d,
>  				     unsigned long addr, unsigned long end,
> -				     pte_fn_t fn, void *data, bool create)
> +				     pte_fn_t fn, void *data, bool create,
> +				     pgtbl_mod_mask *mask)
>  {
>  	pud_t *pud;
>  	unsigned long next;
>  	int err = 0;
>  
>  	if (create) {
> -		pud = pud_alloc(mm, p4d, addr);
> +		pud = pud_alloc_track(mm, p4d, addr, mask);
>  		if (!pud)
>  			return -ENOMEM;
>  	} else {
> @@ -2291,7 +2296,7 @@ static int apply_to_pud_range(struct mm_struct *mm, p4d_t *p4d,
>  		next = pud_addr_end(addr, end);
>  		if (create || !pud_none_or_clear_bad(pud)) {
>  			err = apply_to_pmd_range(mm, pud, addr, next, fn, data,
> -						 create);
> +						 create, mask);
>  			if (err)
>  				break;
>  		}
> @@ -2301,14 +2306,15 @@ static int apply_to_pud_range(struct mm_struct *mm, p4d_t *p4d,
>  
>  static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd,
>  				     unsigned long addr, unsigned long end,
> -				     pte_fn_t fn, void *data, bool create)
> +				     pte_fn_t fn, void *data, bool create,
> +				     pgtbl_mod_mask *mask)
>  {
>  	p4d_t *p4d;
>  	unsigned long next;
>  	int err = 0;
>  
>  	if (create) {
> -		p4d = p4d_alloc(mm, pgd, addr);
> +		p4d = p4d_alloc_track(mm, pgd, addr, mask);
>  		if (!p4d)
>  			return -ENOMEM;
>  	} else {
> @@ -2318,7 +2324,7 @@ static int apply_to_p4d_range(struct mm_struct *mm, pgd_t *pgd,
>  		next = p4d_addr_end(addr, end);
>  		if (create || !p4d_none_or_clear_bad(p4d)) {
>  			err = apply_to_pud_range(mm, p4d, addr, next, fn, data,
> -						 create);
> +						 create, mask);
>  			if (err)
>  				break;
>  		}
> @@ -2333,6 +2339,7 @@ static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr,
>  	pgd_t *pgd;
>  	unsigned long next;
>  	unsigned long end = addr + size;
> +	pgtbl_mod_mask mask = 0;
>  	int err = 0;
>  
>  	if (WARN_ON(addr >= end))
> @@ -2343,11 +2350,14 @@ static int __apply_to_page_range(struct mm_struct *mm, unsigned long addr,
>  		next = pgd_addr_end(addr, end);
>  		if (!create && pgd_none_or_clear_bad(pgd))
>  			continue;
> -		err = apply_to_p4d_range(mm, pgd, addr, next, fn, data, create);
> +		err = apply_to_p4d_range(mm, pgd, addr, next, fn, data, create, &mask);
>  		if (err)
>  			break;
>  	} while (pgd++, addr = next, addr != end);
>  
> +	if (mask & ARCH_PAGE_TABLE_SYNC_MASK)
> +		arch_sync_kernel_mappings(addr, addr + size);
> +
>  	return err;
>  }
>  
> -- 
> 2.28.0
> 

<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>