On Tue, Sep 12, 2017 at 06:54:45PM +0100, Emil Velikov wrote: > On 12 September 2017 at 18:47, Colin Ian King <colin.king@xxxxxxxxxxxxx> wrote: > > On 12/09/17 18:42, Thomas Hellstrom wrote: > >> Hi, Colin, > >> > >> On 09/12/2017 07:35 PM, Colin King wrote: > >>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx> > >>> > >>> mmap'ing the device multiple times will spam the kernel log with the > >>> DRM_ERROR message about illegal mmap'ing the old fifo space. > >> How are you hitting this? Multiple mappings should be fine as long as > >> mapping offsets are correct, > >> so hitting this message should indicate that the user-space app is doing > >> something seriously wrong, and > >> having it present in the log should probably help more than it hurts. > >> > >> /Thomas > > > > Good question. I hit similar issues with the drm qxl driver when > > running some kernel regression tests with stress-ng [1]. I realize this > > is an artificial test scenario so it is definitely not a typical > > use-case, however, sync the illegal mmapping will return -EINVAL the > > application will pick up that this is an error without the need of > > spotting it in the kernel log. And a user space application can perform > > many millions of these invalid mmaps causing kernel log spamming. > > > FWIW I'm the one to "blame" here - pointing Colin to drop the message. > > Two reasons come to mind: > - there is a unwritten rule that roughly says "user input should not > cause kernel log spam" > - out of all the DRM drivers only QXL and VMWGFX print a message, > with a patch addressing the former Maybe we should make this a written rule by patching Documentation/drivers/gpu? Would definitely make sense as part of this patch series. Thanks, Daniel > > HTH > Emil > _______________________________________________ > dri-devel mailing list > dri-devel@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/dri-devel -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
