On Thu, 2025-03-20 at 17:29 +0000, Matthew Auld wrote:
> Handle the case where the hmm range partially covers a huge page
> (like
> 2M), otherwise we can potentially end up doing something nasty like
> mapping memory which potentially is outside the range, and maybe not
> even mapped by the mm. Fix is based on the xe userptr code, which in
> a
> future patch will directly use gpusvm, so needs alignment here.
>
> Reported-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
> Signed-off-by: Matthew Auld <matthew.auld@xxxxxxxxx>
> Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
> ---
> drivers/gpu/drm/drm_gpusvm.c | 25 +++++++++++++++++++++++--
> 1 file changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_gpusvm.c
> b/drivers/gpu/drm/drm_gpusvm.c
> index 2451c816edd5..48993cef4a74 100644
> --- a/drivers/gpu/drm/drm_gpusvm.c
> +++ b/drivers/gpu/drm/drm_gpusvm.c
> @@ -817,6 +817,27 @@ drm_gpusvm_range_alloc(struct drm_gpusvm
> *gpusvm,
> return range;
> }
>
> +/*
> + * To allow skipping PFNs with the same flags (like when they belong
> to
> + * the same huge PTE) when looping over the pfn array, take a given
> a hmm_pfn,
> + * and return the largest order that will fit inside the PTE, but
> also crucially
> + * accounting for the original hmm range boundaries.
> + */
> +static unsigned int drm_gpusvm_hmm_pfn_to_order(unsigned long
> hmm_pfn,
> + unsigned long
> hmm_pfn_index,
> + unsigned long
> npages)
> +{
> + unsigned long size;
> +
> + size = 1UL << hmm_pfn_to_map_order(hmm_pfn);
> + size -= (hmm_pfn & ~HMM_PFN_FLAGS) & (size - 1);
> + hmm_pfn_index += size;
> + if (hmm_pfn_index > npages)
> + size -= (hmm_pfn_index - npages);
> +
> + return fls(size) - 1;
ilog2() for readability?
> +}
> +
> /**
> * drm_gpusvm_check_pages() - Check pages
> * @gpusvm: Pointer to the GPU SVM structure
> @@ -875,7 +896,7 @@ static bool drm_gpusvm_check_pages(struct
> drm_gpusvm *gpusvm,
> err = -EFAULT;
> goto err_free;
> }
> - i += 0x1 << hmm_pfn_to_map_order(pfns[i]);
> + i += 0x1 << drm_gpusvm_hmm_pfn_to_order(pfns[i], i,
> npages);
> }
>
> err_free:
> @@ -1408,7 +1429,7 @@ int drm_gpusvm_range_get_pages(struct
> drm_gpusvm *gpusvm,
> for (i = 0, j = 0; i < npages; ++j) {
> struct page *page = hmm_pfn_to_page(pfns[i]);
>
> - order = hmm_pfn_to_map_order(pfns[i]);
> + order = drm_gpusvm_hmm_pfn_to_order(pfns[i], i,
> npages);
> if (is_device_private_page(page) ||
> is_device_coherent_page(page)) {
> if (zdd != page->zone_device_data && i > 0)
> {
Either way
Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
