Messages in this thread | | | Subject | Re: [PATCH 6/8] drm: Add a drm_get_unmapped_area() helper | From | Christian König <> | Date | Wed, 4 Dec 2019 12:11:23 +0100 |
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Am 03.12.19 um 14:22 schrieb Thomas Hellström (VMware): > From: Thomas Hellstrom <thellstrom@vmware.com> > > This helper is used to align user-space buffer object addresses to > huge page boundaries, minimizing the chance of alignment mismatch > between user-space addresses and physical addresses.
Mhm, I'm wondering if that is really such a good idea.
Wouldn't it be sufficient if userspace uses MAP_HUGETLB?
Regards, Christian.
> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Michal Hocko <mhocko@suse.com> > Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> > Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> > Cc: Ralph Campbell <rcampbell@nvidia.com> > Cc: "Jérôme Glisse" <jglisse@redhat.com> > Cc: "Christian König" <christian.koenig@amd.com> > Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com> > --- > drivers/gpu/drm/drm_file.c | 130 +++++++++++++++++++++++++++++++++++++ > include/drm/drm_file.h | 5 ++ > 2 files changed, 135 insertions(+) > > diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c > index ea34bc991858..e5b4024cd397 100644 > --- a/drivers/gpu/drm/drm_file.c > +++ b/drivers/gpu/drm/drm_file.c > @@ -31,6 +31,8 @@ > * OTHER DEALINGS IN THE SOFTWARE. > */ > > +#include <uapi/asm/mman.h> > + > #include <linux/dma-fence.h> > #include <linux/module.h> > #include <linux/pci.h> > @@ -41,6 +43,7 @@ > #include <drm/drm_drv.h> > #include <drm/drm_file.h> > #include <drm/drm_print.h> > +#include <drm/drm_vma_manager.h> > > #include "drm_crtc_internal.h" > #include "drm_internal.h" > @@ -754,3 +757,130 @@ void drm_send_event(struct drm_device *dev, struct drm_pending_event *e) > spin_unlock_irqrestore(&dev->event_lock, irqflags); > } > EXPORT_SYMBOL(drm_send_event); > + > +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > +/* > + * drm_addr_inflate() attempts to construct an aligned area by inflating > + * the area size and skipping the unaligned start of the area. > + * adapted from shmem_get_unmapped_area() > + */ > +static unsigned long drm_addr_inflate(unsigned long addr, > + unsigned long len, > + unsigned long pgoff, > + unsigned long flags, > + unsigned long huge_size) > +{ > + unsigned long offset, inflated_len; > + unsigned long inflated_addr; > + unsigned long inflated_offset; > + > + offset = (pgoff << PAGE_SHIFT) & (huge_size - 1); > + if (offset && offset + len < 2 * huge_size) > + return addr; > + if ((addr & (huge_size - 1)) == offset) > + return addr; > + > + inflated_len = len + huge_size - PAGE_SIZE; > + if (inflated_len > TASK_SIZE) > + return addr; > + if (inflated_len < len) > + return addr; > + > + inflated_addr = current->mm->get_unmapped_area(NULL, 0, inflated_len, > + 0, flags); > + if (IS_ERR_VALUE(inflated_addr)) > + return addr; > + if (inflated_addr & ~PAGE_MASK) > + return addr; > + > + inflated_offset = inflated_addr & (huge_size - 1); > + inflated_addr += offset - inflated_offset; > + if (inflated_offset > offset) > + inflated_addr += huge_size; > + > + if (inflated_addr > TASK_SIZE - len) > + return addr; > + > + return inflated_addr; > +} > + > +/** > + * drm_get_unmapped_area() - Get an unused user-space virtual memory area > + * suitable for huge page table entries. > + * @file: The struct file representing the address space being mmap()'d. > + * @uaddr: Start address suggested by user-space. > + * @len: Length of the area. > + * @pgoff: The page offset into the address space. > + * @flags: mmap flags > + * @mgr: The address space manager used by the drm driver. This argument can > + * probably be removed at some point when all drivers use the same > + * address space manager. > + * > + * This function attempts to find an unused user-space virtual memory area > + * that can accommodate the size we want to map, and that is properly > + * aligned to facilitate huge page table entries matching actual > + * huge pages or huge page aligned memory in buffer objects. Buffer objects > + * are assumed to start at huge page boundary pfns (io memory) or be > + * populated by huge pages aligned to the start of the buffer object > + * (system- or coherent memory). Adapted from shmem_get_unmapped_area. > + * > + * Return: aligned user-space address. > + */ > +unsigned long drm_get_unmapped_area(struct file *file, > + unsigned long uaddr, unsigned long len, > + unsigned long pgoff, unsigned long flags, > + struct drm_vma_offset_manager *mgr) > +{ > + unsigned long addr; > + unsigned long inflated_addr; > + struct drm_vma_offset_node *node; > + > + if (len > TASK_SIZE) > + return -ENOMEM; > + > + /* Adjust mapping offset to be zero at bo start */ > + drm_vma_offset_lock_lookup(mgr); > + node = drm_vma_offset_lookup_locked(mgr, pgoff, 1); > + if (node) > + pgoff -= node->vm_node.start; > + drm_vma_offset_unlock_lookup(mgr); > + > + addr = current->mm->get_unmapped_area(file, uaddr, len, pgoff, flags); > + if (IS_ERR_VALUE(addr)) > + return addr; > + if (addr & ~PAGE_MASK) > + return addr; > + if (addr > TASK_SIZE - len) > + return addr; > + > + if (len < HPAGE_PMD_SIZE) > + return addr; > + if (flags & MAP_FIXED) > + return addr; > + /* > + * Our priority is to support MAP_SHARED mapped hugely; > + * and support MAP_PRIVATE mapped hugely too, until it is COWed. > + * But if caller specified an address hint, respect that as before. > + */ > + if (uaddr) > + return addr; > + > + inflated_addr = drm_addr_inflate(addr, len, pgoff, flags, > + HPAGE_PMD_SIZE); > + > + if (IS_ENABLED(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) && > + len >= HPAGE_PUD_SIZE) > + inflated_addr = drm_addr_inflate(inflated_addr, len, pgoff, > + flags, HPAGE_PUD_SIZE); > + return inflated_addr; > +} > +#else /* CONFIG_TRANSPARENT_HUGEPAGE */ > +unsigned long drm_get_unmapped_area(struct file *file, > + unsigned long uaddr, unsigned long len, > + unsigned long pgoff, unsigned long flags, > + struct drm_vma_offset_manager *mgr) > +{ > + return current->mm->get_unmapped_area(file, uaddr, len, pgoff, flags); > +} > +#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ > +EXPORT_SYMBOL_GPL(drm_get_unmapped_area); > diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h > index 67af60bb527a..4719cc80d547 100644 > --- a/include/drm/drm_file.h > +++ b/include/drm/drm_file.h > @@ -386,5 +386,10 @@ void drm_event_cancel_free(struct drm_device *dev, > struct drm_pending_event *p); > void drm_send_event_locked(struct drm_device *dev, struct drm_pending_event *e); > void drm_send_event(struct drm_device *dev, struct drm_pending_event *e); > +struct drm_vma_offset_manager; > +unsigned long drm_get_unmapped_area(struct file *file, > + unsigned long uaddr, unsigned long len, > + unsigned long pgoff, unsigned long flags, > + struct drm_vma_offset_manager *mgr); > > #endif /* _DRM_FILE_H_ */
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