On Wed, Sep 11, 2019 at 03:28:27PM -0700, Ralph Campbell wrote:
> Allow hmm_range_fault() to return success (0) when the CPU pagetable
> entry points to the special shared zero page.
> The caller can then handle the zero page by possibly clearing device
> private memory instead of DMAing a zero page.
>
> Signed-off-by: Ralph Campbell <[email protected]>
> Cc: "Jérôme Glisse" <[email protected]>
> Cc: Jason Gunthorpe <[email protected]>
> Cc: Christoph Hellwig <[email protected]>
> ---
> mm/hmm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 06041d4399ff..7217912bef13 100644
> --- a/mm/hmm.c
> +++ b/mm/hmm.c
> @@ -532,7 +532,7 @@ static int hmm_vma_handle_pte(struct mm_walk *walk,
> unsigned long addr,
> return -EBUSY;
> } else if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL) && pte_special(pte))
> {
> *pfn = range->values[HMM_PFN_SPECIAL];
> - return -EFAULT;
> + return is_zero_pfn(pte_pfn(pte)) ? 0 : -EFAULT;
Any chance to just use a normal if here:
if (!is_zero_pfn(pte_pfn(pte)))
return -EFAULT;
return 0;
