[PATCH V2] cxl: Fix memory page not handled

[Andrew Donnellan]

On 25/09/17 18:58, Christophe Lombard wrote:
> The in-kernel 'library' API can be called by drivers to help
> interaction with an IBM XSL on a POWER9 system.
> 
> The cxllib_handle_fault() API is used to handle memory fault. All memory
> pages of the specified buffer have to be handled but under certain
> conditions,the last page may not be touched, and the address the
> adapter is trying to access is never sent to the kernel for resolution.
> 
> This patch reworks start address of the loop with an address aligned on
> the page size. In this context, the last page is not missed.
> 
> Signed-off-by: Christophe Lombard <clombard at linux.vnet.ibm.com>
> 
> Fixes: 3ced8d730063 ("cxl: Export library to support IBM XSL");

The duplication of the find_vma() depresses me slightly but I suppose 
there's not much that can be done there :)

Acked-by: Andrew Donnellan <andrew.donnellan at au1.ibm.com>

> 
> ---
> Changelog[v2]
>   - Rebase to latest upstream.
>   - Change the start address of the loop.
>   - Rewrite the commit message.
> ---
>   drivers/misc/cxl/cxllib.c | 13 +++++++++++--
>   1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/misc/cxl/cxllib.c b/drivers/misc/cxl/cxllib.c
> index 5dba23c..ff7492d 100644
> --- a/drivers/misc/cxl/cxllib.c
> +++ b/drivers/misc/cxl/cxllib.c
> @@ -219,8 +219,17 @@ int cxllib_handle_fault(struct mm_struct *mm, u64 addr, u64 size, u64 flags)
>   
>   	down_read(&mm->mmap_sem);
>   
> -	for (dar = addr; dar < addr + size; dar += page_size) {
> -		if (!vma || dar < vma->vm_start || dar > vma->vm_end) {
> +	vma = find_vma(mm, addr);
> +	if (!vma) {
> +		pr_err("Can't find vma for addr %016llx\n", addr);
> +		rc = -EFAULT;
> +		goto out;
> +	}
> +	/* get the size of the pages allocated */
> +	page_size = vma_kernel_pagesize(vma);
> +
> +	for (dar = (addr & ~(page_size - 1)); dar < (addr + size); dar += page_size) {
> +		if (dar < vma->vm_start || dar > vma->vm_end) {
>   			vma = find_vma(mm, addr);
>   			if (!vma) {
>   				pr_err("Can't find vma for addr %016llx\n", addr);
> 

-- 
Andrew Donnellan              OzLabs, ADL Canberra
andrew.donnellan at au1.ibm.com  IBM Australia Limited