Re: [PATCH 1/2]: mm: Make vmalloc_user() align base kernel virtual address to SHMLBA.

[Ingo Molnar <mingo@elte.hu>]

( Andrew, this patch has mm/* effects - any objections? Would still like
  to get this into v2.6.32. )

* David Miller <davem@davemloft.net> wrote:

> When a vmalloc'd area is mmap'd into userspace, some kind of 
> co-ordination is necessary for this to work on platforms with cpu 
> D-caches which can have aliases.
> 
> Otherwise kernel side writes won't be seen properly in userspace and
> vice versa.
> 
> If the kernel side mapping and the user side one have the same
> alignment, modulo SHMLBA, this can work as long as VM_SHARED is
> shared of VMA and for all current users this is true.  VM_SHARED
> will force SHMLBA alignment of the user side mmap on platforms
> with D-cache aliasing matters.
> 
> The bulk of this patch is just making it so that a specific alignment
> can be passed down into __get_vm_area_node().  All existing callers
> pass in '1' which preserves existing behavior.  vmalloc_user() gives
> SHMLBA for the alignment.
> 
> As a side effect this should get the video media drivers and other
> vmalloc_user() users into more working shape on such systems.
> 
> Signed-off-by: David S. Miller <davem@davemloft.net>
> ---
>  mm/vmalloc.c |   48 ++++++++++++++++++++++++++----------------------
>  1 files changed, 26 insertions(+), 22 deletions(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index f8189a4..be15e03 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -29,6 +29,7 @@
>  #include <asm/atomic.h>
>  #include <asm/uaccess.h>
>  #include <asm/tlbflush.h>
> +#include <asm/shmparam.h>
>  
>  
>  /*** Page table manipulation functions ***/
> @@ -1123,13 +1124,12 @@ DEFINE_RWLOCK(vmlist_lock);
>  struct vm_struct *vmlist;
>  
>  static struct vm_struct *__get_vm_area_node(unsigned long size,
> -		unsigned long flags, unsigned long start, unsigned long end,
> -		int node, gfp_t gfp_mask, void *caller)
> +		unsigned long align, unsigned long flags, unsigned long start,
> +		unsigned long end, int node, gfp_t gfp_mask, void *caller)
>  {
>  	static struct vmap_area *va;
>  	struct vm_struct *area;
>  	struct vm_struct *tmp, **p;
> -	unsigned long align = 1;
>  
>  	BUG_ON(in_interrupt());
>  	if (flags & VM_IOREMAP) {
> @@ -1187,7 +1187,7 @@ static struct vm_struct *__get_vm_area_node(unsigned long size,
>  struct vm_struct *__get_vm_area(unsigned long size, unsigned long flags,
>  				unsigned long start, unsigned long end)
>  {
> -	return __get_vm_area_node(size, flags, start, end, -1, GFP_KERNEL,
> +	return __get_vm_area_node(size, 1, flags, start, end, -1, GFP_KERNEL,
>  						__builtin_return_address(0));
>  }
>  EXPORT_SYMBOL_GPL(__get_vm_area);
> @@ -1196,7 +1196,7 @@ struct vm_struct *__get_vm_area_caller(unsigned long size, unsigned long flags,
>  				       unsigned long start, unsigned long end,
>  				       void *caller)
>  {
> -	return __get_vm_area_node(size, flags, start, end, -1, GFP_KERNEL,
> +	return __get_vm_area_node(size, 1, flags, start, end, -1, GFP_KERNEL,
>  				  caller);
>  }
>  
> @@ -1211,22 +1211,22 @@ struct vm_struct *__get_vm_area_caller(unsigned long size, unsigned long flags,
>   */
>  struct vm_struct *get_vm_area(unsigned long size, unsigned long flags)
>  {
> -	return __get_vm_area_node(size, flags, VMALLOC_START, VMALLOC_END,
> +	return __get_vm_area_node(size, 1, flags, VMALLOC_START, VMALLOC_END,
>  				-1, GFP_KERNEL, __builtin_return_address(0));
>  }
>  
>  struct vm_struct *get_vm_area_caller(unsigned long size, unsigned long flags,
>  				void *caller)
>  {
> -	return __get_vm_area_node(size, flags, VMALLOC_START, VMALLOC_END,
> +	return __get_vm_area_node(size, 1, flags, VMALLOC_START, VMALLOC_END,
>  						-1, GFP_KERNEL, caller);
>  }
>  
>  struct vm_struct *get_vm_area_node(unsigned long size, unsigned long flags,
>  				   int node, gfp_t gfp_mask)
>  {
> -	return __get_vm_area_node(size, flags, VMALLOC_START, VMALLOC_END, node,
> -				  gfp_mask, __builtin_return_address(0));
> +	return __get_vm_area_node(size, 1, flags, VMALLOC_START, VMALLOC_END,
> +				  node, gfp_mask, __builtin_return_address(0));
>  }
>  
>  static struct vm_struct *find_vm_area(const void *addr)
> @@ -1385,7 +1385,8 @@ void *vmap(struct page **pages, unsigned int count,
>  }
>  EXPORT_SYMBOL(vmap);
>  
> -static void *__vmalloc_node(unsigned long size, gfp_t gfp_mask, pgprot_t prot,
> +static void *__vmalloc_node(unsigned long size, unsigned long align,
> +			    gfp_t gfp_mask, pgprot_t prot,
>  			    int node, void *caller);
>  static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
>  				 pgprot_t prot, int node, void *caller)
> @@ -1399,7 +1400,7 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
>  	area->nr_pages = nr_pages;
>  	/* Please note that the recursion is strictly bounded. */
>  	if (array_size > PAGE_SIZE) {
> -		pages = __vmalloc_node(array_size, gfp_mask | __GFP_ZERO,
> +		pages = __vmalloc_node(array_size, 1, gfp_mask | __GFP_ZERO,
>  				PAGE_KERNEL, node, caller);
>  		area->flags |= VM_VPAGES;
>  	} else {
> @@ -1458,6 +1459,7 @@ void *__vmalloc_area(struct vm_struct *area, gfp_t gfp_mask, pgprot_t prot)
>  /**
>   *	__vmalloc_node  -  allocate virtually contiguous memory
>   *	@size:		allocation size
> + *	@align:		desired alignment
>   *	@gfp_mask:	flags for the page level allocator
>   *	@prot:		protection mask for the allocated pages
>   *	@node:		node to use for allocation or -1
> @@ -1467,8 +1469,9 @@ void *__vmalloc_area(struct vm_struct *area, gfp_t gfp_mask, pgprot_t prot)
>   *	allocator with @gfp_mask flags.  Map them into contiguous
>   *	kernel virtual space, using a pagetable protection of @prot.
>   */
> -static void *__vmalloc_node(unsigned long size, gfp_t gfp_mask, pgprot_t prot,
> -						int node, void *caller)
> +static void *__vmalloc_node(unsigned long size, unsigned long align,
> +			    gfp_t gfp_mask, pgprot_t prot,
> +			    int node, void *caller)
>  {
>  	struct vm_struct *area;
>  	void *addr;
> @@ -1478,8 +1481,8 @@ static void *__vmalloc_node(unsigned long size, gfp_t gfp_mask, pgprot_t prot,
>  	if (!size || (size >> PAGE_SHIFT) > num_physpages)
>  		return NULL;
>  
> -	area = __get_vm_area_node(size, VM_ALLOC, VMALLOC_START, VMALLOC_END,
> -						node, gfp_mask, caller);
> +	area = __get_vm_area_node(size, align, VM_ALLOC, VMALLOC_START,
> +				  VMALLOC_END, node, gfp_mask, caller);
>  
>  	if (!area)
>  		return NULL;
> @@ -1498,7 +1501,7 @@ static void *__vmalloc_node(unsigned long size, gfp_t gfp_mask, pgprot_t prot,
>  
>  void *__vmalloc(unsigned long size, gfp_t gfp_mask, pgprot_t prot)
>  {
> -	return __vmalloc_node(size, gfp_mask, prot, -1,
> +	return __vmalloc_node(size, 1, gfp_mask, prot, -1,
>  				__builtin_return_address(0));
>  }
>  EXPORT_SYMBOL(__vmalloc);
> @@ -1514,7 +1517,7 @@ EXPORT_SYMBOL(__vmalloc);
>   */
>  void *vmalloc(unsigned long size)
>  {
> -	return __vmalloc_node(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
> +	return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
>  					-1, __builtin_return_address(0));
>  }
>  EXPORT_SYMBOL(vmalloc);
> @@ -1531,7 +1534,8 @@ void *vmalloc_user(unsigned long size)
>  	struct vm_struct *area;
>  	void *ret;
>  
> -	ret = __vmalloc_node(size, GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
> +	ret = __vmalloc_node(size, SHMLBA,
> +			     GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
>  			     PAGE_KERNEL, -1, __builtin_return_address(0));
>  	if (ret) {
>  		area = find_vm_area(ret);
> @@ -1554,7 +1558,7 @@ EXPORT_SYMBOL(vmalloc_user);
>   */
>  void *vmalloc_node(unsigned long size, int node)
>  {
> -	return __vmalloc_node(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
> +	return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL,
>  					node, __builtin_return_address(0));
>  }
>  EXPORT_SYMBOL(vmalloc_node);
> @@ -1577,7 +1581,7 @@ EXPORT_SYMBOL(vmalloc_node);
>  
>  void *vmalloc_exec(unsigned long size)
>  {
> -	return __vmalloc_node(size, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC,
> +	return __vmalloc_node(size, 1, GFP_KERNEL | __GFP_HIGHMEM, PAGE_KERNEL_EXEC,
>  			      -1, __builtin_return_address(0));
>  }
>  
> @@ -1598,7 +1602,7 @@ void *vmalloc_exec(unsigned long size)
>   */
>  void *vmalloc_32(unsigned long size)
>  {
> -	return __vmalloc_node(size, GFP_VMALLOC32, PAGE_KERNEL,
> +	return __vmalloc_node(size, 1, GFP_VMALLOC32, PAGE_KERNEL,
>  			      -1, __builtin_return_address(0));
>  }
>  EXPORT_SYMBOL(vmalloc_32);
> @@ -1615,7 +1619,7 @@ void *vmalloc_32_user(unsigned long size)
>  	struct vm_struct *area;
>  	void *ret;
>  
> -	ret = __vmalloc_node(size, GFP_VMALLOC32 | __GFP_ZERO, PAGE_KERNEL,
> +	ret = __vmalloc_node(size, 1, GFP_VMALLOC32 | __GFP_ZERO, PAGE_KERNEL,
>  			     -1, __builtin_return_address(0));
>  	if (ret) {
>  		area = find_vm_area(ret);
> -- 
> 1.6.4.2