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    Subject[PATCH 6/8] drm: Add a drm_get_unmapped_area() helper
    Date
    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.

    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_ */
    --
    2.21.0
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