Messages in this thread | | | Date | Fri, 14 Oct 2022 09:03:21 +0200 | Subject | Re: [PATCH] drm/radeon: Replace kmap() with kmap_local_page() | From | Christian König <> |
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Am 13.10.22 um 23:07 schrieb Fabio M. De Francesco: > The use of kmap() is being deprecated in favor of kmap_local_page(). > > There are two main problems with kmap(): (1) It comes with an overhead as > the mapping space is restricted and protected by a global lock for > synchronization and (2) it also requires global TLB invalidation when the > kmap’s pool wraps and it might block when the mapping space is fully > utilized until a slot becomes available. > > With kmap_local_page() the mappings are per thread, CPU local, can take > page faults, and can be called from any context (including interrupts). > It is faster than kmap() in kernels with HIGHMEM enabled. Furthermore, > the tasks can be preempted and, when they are scheduled to run again, the > kernel virtual addresses are restored and still valid. > > Therefore, replace kmap() with kmap_local_page() in radeon_ttm_gtt_read(). > > Cc: "Venkataramanan, Anirudh" <anirudh.venkataramanan@intel.com> > Suggested-by: Ira Weiny <ira.weiny@intel.com> > Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
> --- > drivers/gpu/drm/radeon/radeon_ttm.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/radeon/radeon_ttm.c b/drivers/gpu/drm/radeon/radeon_ttm.c > index d33fec488713..bdb4c0e0736b 100644 > --- a/drivers/gpu/drm/radeon/radeon_ttm.c > +++ b/drivers/gpu/drm/radeon/radeon_ttm.c > @@ -869,11 +869,11 @@ static ssize_t radeon_ttm_gtt_read(struct file *f, char __user *buf, > > page = rdev->gart.pages[p]; > if (page) { > - ptr = kmap(page); > + ptr = kmap_local_page(page); > ptr += off; > > r = copy_to_user(buf, ptr, cur_size); > - kunmap(rdev->gart.pages[p]); > + kunmap_local(ptr); > } else > r = clear_user(buf, cur_size); >
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