On Wed, Aug 25, 2021 at 12:38:31PM +0200, David Hildenbrand wrote: > On 25.08.21 12:20, Catalin Marinas wrote: > > On Tue, Aug 24, 2021 at 08:59:22PM +0200, David Hildenbrand wrote: > > > On 24.08.21 20:46, Robin Murphy wrote: > > > > On 2021-08-24 19:28, Mike Rapoport wrote: > > > > > On Tue, Aug 24, 2021 at 06:37:41PM +0100, Catalin Marinas wrote: > > > > > > On Tue, Aug 24, 2021 at 03:40:47PM +0200, Alex Bee wrote: > > > > > > > it seems there is a regression in arm64 memory mapping in 5.14, since it > > > > > > > fails on Rockchip RK3328 when the pl330 dmac tries to map with: > > > > > > > > > > > > > > ------------[ cut here ]------------ > > > > > > > WARNING: CPU: 2 PID: 373 at kernel/dma/mapping.c:235 dma_map_resource+0x68/0xc0 > > > > > > > Modules linked in: spi_rockchip(+) fuse > > > > > > > CPU: 2 PID: 373 Comm: systemd-udevd Not tainted 5.14.0-rc7 #1 > > > > > > > Hardware name: Pine64 Rock64 (DT) > > > > > > > pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=--) > > > > > > > pc : dma_map_resource+0x68/0xc0 > > > > > > > lr : pl330_prep_slave_fifo+0x78/0xd0 > > > > > > > sp : ffff800012102ae0 > > > > > > > x29: ffff800012102ae0 x28: ffff000005c94800 x27: 0000000000000000 > > > > > > > x26: ffff000000566bd0 x25: 0000000000000001 x24: 0000000000000001 > > > > > > > x23: 0000000000000002 x22: ffff000000628c00 x21: 0000000000000001 > > > > > > > x20: ffff000000566bd0 x19: 0000000000000001 x18: 0000000000000000 > > > > > > > x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 > > > > > > > x14: 0000000000000277 x13: 0000000000000001 x12: 0000000000000000 > > > > > > > x11: 0000000000000001 x10: 00000000000008e0 x9 : ffff800012102a80 > > > > > > > x8 : ffff000000d14b80 x7 : ffff0000fe7b12f0 x6 : ffff0000fe7b1100 > > > > > > > x5 : fffffc000000000f x4 : 0000000000000000 x3 : 0000000000000001 > > > > > > > x2 : 0000000000000001 x1 : 00000000ff190800 x0 : ffff000000628c00 > > > > > > > Call trace: > > > > > > > dma_map_resource+0x68/0xc0 > > > > > > > pl330_prep_slave_sg+0x58/0x220 > > > > > > > rockchip_spi_prepare_dma+0xd8/0x2c0 [spi_rockchip] > > > > > > > rockchip_spi_transfer_one+0x294/0x3d8 [spi_rockchip] > > > > > > [...] > > > > > > > Note: This does not relate to the spi driver - when disabling this device in > > > > > > > the device tree it fails for any other (i2s, for instance) which uses dma. > > > > > > > Commenting out the failing check at [1], however, helps and the mapping > > > > > > > works again. > > > > > > > > > > > Do you know which address dma_map_resource() is trying to map (maybe > > > > > > add some printk())? It's not supposed to map RAM, hence the warning. > > > > > > Random guess, the address is 0xff190800 (based on the x1 above but the > > > > > > regs might as well be mangled). > > > > > > > > > > 0xff190800 will cause this warning for sure. It has a memory map, but it is > > > > > not RAM so old version of pfn_valid() would return 0 and the new one > > > > > returns 1. > > > > > > > > How does that happen, though? It's not a memory address, and it's not > > > > even within the bounds of anywhere there should or could be memory. This > > > > SoC has a simple memory map - everything from 0 to 0xfeffffff goes to > > > > the DRAM controller (which may not all be populated, and may have pieces > > > > carved out by secure firmware), while 0xff000000-0xffffffff is MMIO. Why > > > > do we have pages (or at least the assumption of pages) for somewhere > > > > which by all rights should not have them? > > > > > > Simple: we allocate the vmemmap for whole sections (e.g., 128 MiB) to avoid > > > any such hacks. If there is a memory hole, it gets a memmap as well. > > > > > > Tricking pfn_valid() into returning "false" where we actually have a memmap > > > only makes it look like there is no memmap; but there is one, and > > > it's PG_reserved. > > > > I can see the documentation for pfn_valid() does not claim anything more > > than the presence of an memmap entry. But I wonder whether the confusion > > is wider-spread than just the DMA code. At a quick grep, try_ram_remap() > > assumes __va() can be used on pfn_valid(), though I suspect it relies on > > the calling function to check that the resource was RAM. The arm64 > > kern_addr_valid() returns true based on pfn_valid() and kcore.c uses > > standard memcpy on it, which wouldn't work for I/O (should we change > > this check to pfn_is_map_memory() for arm64?). > > kern_addr_valid() checks that there is a direct map entry, and that the > mapped address has a valid mmap. (copied from x86-64) It checks that there is a va->pa mapping, not necessarily in the linear map as it walks the page tables. So for some I/O range that happens to be mapped but which was in close proximity to RAM so that pfn_valid() is true, kern_addr_valid() would return true. I don't thin that was the intention. > Would you expect to have a direct map for memory holes and similar (IOW, > !System RAM)? No, but we with the generic pfn_valid(), it may return true for mapped MMIO (with different attributes than the direct map). > > > > > > Either pfn_valid() gets confused in 5.14 or something is wrong with the > > > > > > DT. I have a suspicion it's the former since reverting the above commit > > > > > > makes it disappear. > > > > > > > > > > I think pfn_valid() actually behaves as expected but the caller is wrong > > > > > because pfn_valid != RAM (this applies btw to !arm64 as well). > > > > > > > > > > /* Don't allow RAM to be mapped */ > > > > > if (WARN_ON_ONCE(pfn_valid(PHYS_PFN(phys_addr)))) > > > > > return DMA_MAPPING_ERROR; > > > > > > > > > > Alex, can you please try this patch: > > > > > > > > That will certainly paper over the issue, but it's avoiding the question > > > > of what went wrong with the memory map in the first place. The comment > > > > is indeed a bit inaccurate, but ultimately dma_map_resource() exists for > > > > addresses that would be wrong to pass to dma_map_page(), so I believe > > > > pfn_valid() is still the correct check. > > > > > > If we want to check for RAM, pfn_valid() would be wrong. If we want to check > > > for "is there a memmap, for whatever lives or does not live there", > > > pfn_valid() is the right check. > > > > So what should the DMA code use instead? Last time we needed something > > similar, the recommendation was to use pfn_to_online_page(). Mike is > > suggesting memblock_is_memory(). > > We use pfn_to_online_page() when we want to know if it's system RAM and that > the memmap actually contains something sane (-> memmap content has a well > defined state). > > You can have offline memory blocks where pfn_to_online_page() would return > "false", memblock_is_memory() would return "true". IOW, there is a memmap, > it's System RAM, but the memmap is stale and not trustworthy. > > If you want to make sure no System RAM (online/offline/...) will get mapped, > memblock_is_memory() should be the right thing to use. I recall that x86 > traverse the resource tree instead to exclude system ram regions similarly. Thanks, this makes sense. -- Catalin
