On Wed, Nov 30, 2022 at 11:07:32AM -0500, Alex Deucher wrote: > On Wed, Nov 30, 2022 at 10:42 AM Robin Murphy <robin.murphy@xxxxxxx> wrote: > > > > On 2022-11-30 14:28, Alex Deucher wrote: > > > On Wed, Nov 30, 2022 at 7:54 AM Robin Murphy <robin.murphy@xxxxxxx> wrote: > > >> > > >> On 2022-11-29 17:11, Mikhail Krylov wrote: > > >>> On Tue, Nov 29, 2022 at 11:05:28AM -0500, Alex Deucher wrote: > > >>>> On Tue, Nov 29, 2022 at 10:59 AM Mikhail Krylov <sqarert@xxxxxxxxx> wrote: > > >>>>> > > >>>>> On Tue, Nov 29, 2022 at 09:44:19AM -0500, Alex Deucher wrote: > > >>>>>> On Mon, Nov 28, 2022 at 3:48 PM Mikhail Krylov <sqarert@xxxxxxxxx> wrote: > > >>>>>>> > > >>>>>>> On Mon, Nov 28, 2022 at 09:50:50AM -0500, Alex Deucher wrote: > > >>>>>>> > > >>>>>>>>>> [excessive quoting removed] > > >>>>>>> > > >>>>>>>>> So, is there any progress on this issue? I do understand it's not a high > > >>>>>>>>> priority one, and today I've checked it on 6.0 kernel, and > > >>>>>>>>> unfortunately, it still persists... > > >>>>>>>>> > > >>>>>>>>> I'm considering writing a patch that will allow user to override > > >>>>>>>>> need_dma32/dma_bits setting with a module parameter. I'll have some time > > >>>>>>>>> after the New Year for that. > > >>>>>>>>> > > >>>>>>>>> Is it at all possible that such a patch will be merged into kernel? > > >>>>>>>>> > > >>>>>>>> On Mon, Nov 28, 2022 at 9:31 AM Mikhail Krylov <sqarert@xxxxxxxxx> wrote: > > >>>>>>>> Unless someone familiar with HIMEM can figure out what is going wrong > > >>>>>>>> we should just revert the patch. > > >>>>>>>> > > >>>>>>>> Alex > > >>>>>>> > > >>>>>>> > > >>>>>>> Okay, I was suggesting that mostly because > > >>>>>>> > > >>>>>>> a) it works for me with dma_bits = 40 (I understand that's what it is > > >>>>>>> without the original patch applied); > > >>>>>>> > > >>>>>>> b) there's a hint of uncertainity on this line > > >>>>>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/radeon/radeon_device.c#n1359 > > >>>>>>> saying that for AGP dma_bits = 32 is the safest option, so apparently there are > > >>>>>>> setups, unlike mine, where dma_bits = 32 is better than 40. > > >>>>>>> > > >>>>>>> But I'm in no position to argue, just wanted to make myself clear. > > >>>>>>> I'm okay with rebuilding the kernel for my machine until the original > > >>>>>>> patch is reverted or any other fix is applied. > > >>>>>> > > >>>>>> What GPU do you have and is it AGP? If it is AGP, does setting > > >>>>>> radeon.agpmode=-1 also fix it? > > >>>>>> > > >>>>>> Alex > > >>>>> > > >>>>> That is ATI Radeon X1950, and, unfortunately, radeon.agpmode=-1 doesn't > > >>>>> help, it just makes 3D acceleration in games such as OpenArena stop > > >>>>> working. > > >>>> > > >>>> Just to confirm, is the board AGP or PCIe? > > >>>> > > >>>> Alex > > >>> > > >>> It is AGP. That's an old machine. > > >> > > >> Can you check whether dma_addressing_limited() is actually returning the > > >> expected result at the point of radeon_ttm_init()? Disabling highmem is > > >> presumably just hiding whatever problem exists, by throwing away all > > >> >32-bit RAM such that use_dma32 doesn't matter. > > > > > > The device in question only supports a 32 bit DMA mask so > > > dma_addressing_limited() should return true. Bounce buffers are not > > > really usable on GPUs because they map so much memory. If > > > dma_addressing_limited() returns false, that would explain it. > > > > Right, it appears to be the only part of the offending commit that > > *could* reasonably make any difference, so I'm primarily wondering if > > dma_get_required_mask() somehow gets confused. > > Mikhail, > > Can you see that dma_addressing_limited() and dma_get_required_mask() > return in this case? > > Alex > > > > > > Thanks, > > Robin. Unfortunately, right now I don't have enough time for kernel modifications and rebuilds (I will later!), so I did a quick-and-dirty research with kprobe. The problem is that dma_addressing_limited() seems to be inlined and kprobe fails to intercept it. But I managed to get the result of dma_get_required_mask(). It returns 0x7fffffff (!) on the vanilla (with the patch, buggy) kernel: $ sudo kprobe-perf 'r:dma_get_required_mask $retval' Tracing kprobe dma_get_required_mask. Ctrl-C to end. modprobe-1244 [000] d... 105.582816: dma_get_required_mask: (radeon_ttm_init+0x61/0x240 [radeon] <- dma_get_required_mask) arg1=0x7fffffff This function does not even get called in the kernel without the patch that I built myself. I believe that's because ttm_bo_device_init() doesn't call it without the patch. Hope that helps at least a bit. If not, I'll be able to do more thorough research in a couple of weeks, probably.
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