Re: Bug 205201 - overflow of DMA mask and bus mask

From: Christian Zigotzky
Date: Thu Nov 07 2019 - 04:53:22 EST

On 05 November 2019 at 5:28 pm, Christoph Hellwig wrote:
On Tue, Nov 05, 2019 at 08:56:27AM +0100, Christian Zigotzky wrote:
Hi All,

We still have DMA problems with some PCI devices. Since the PowerPC updates
4.21-1 [1] we need to decrease the RAM to 3500MB (mem=3500M) if we want to
work with our PCI devices. The FSL P5020 and P5040 have these problems
currently.

Error message:

[ÂÂ 25.654852] bttv 1000:04:05.0: overflow 0x00000000fe077000+4096 of DMA
mask ffffffff bus mask df000000

All 5.x Linux kernels can't initialize a SCSI PCI card anymore so booting
of a Linux userland isn't possible.

PLEASE check the DMA changes in the PowerPC updates 4.21-1 [1]. The kernel
4.20 works with all PCI devices without limitation of RAM.
Can you send me the .config and a dmesg? And in the meantime try the
patch below?

---
>From 4d659b7311bd4141fdd3eeeb80fa2d7602ea01d4 Mon Sep 17 00:00:00 2001
From: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
Date: Fri, 18 Oct 2019 13:00:43 +0200
Subject: dma-direct: check for overflows on 32 bit DMA addresses

As seen on the new Raspberry Pi 4 and sta2x11's DMA implementation it is
possible for a device configured with 32 bit DMA addresses and a partial
DMA mapping located at the end of the address space to overflow. It
happens when a higher physical address, not DMAable, is translated to
it's DMA counterpart.

For example the Raspberry Pi 4, configurable up to 4 GB of memory, has
an interconnect capable of addressing the lower 1 GB of physical memory
with a DMA offset of 0xc0000000. It transpires that, any attempt to
translate physical addresses higher than the first GB will result in an
overflow which dma_capable() can't detect as it only checks for
addresses bigger then the maximum allowed DMA address.

Fix this by verifying in dma_capable() if the DMA address range provided
is at any point lower than the minimum possible DMA address on the bus.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
---
include/linux/dma-direct.h | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index adf993a3bd58..6ad9e9ea7564 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -3,6 +3,7 @@
#define _LINUX_DMA_DIRECT_H 1
#include <linux/dma-mapping.h>
+#include <linux/memblock.h> /* for min_low_pfn */
#include <linux/mem_encrypt.h>
#ifdef CONFIG_ARCH_HAS_PHYS_TO_DMA
@@ -27,6 +28,13 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
if (!dev->dma_mask)
return false;
+#ifndef CONFIG_ARCH_DMA_ADDR_T_64BIT
+ /* Check if DMA address overflowed */
+ if (min(addr, addr + size - 1) <
+ __phys_to_dma(dev, (phys_addr_t)(min_low_pfn << PAGE_SHIFT)))
+ return false;
+#endif
+
return addr + size - 1 <=
min_not_zero(*dev->dma_mask, dev->bus_dma_mask);
}
Hello Christoph,

Thanks a lot for your patch! Unfortunately this patch doesn't solve the issue.

Error messages:

[ÂÂÂ 6.041163] bttv: driver version 0.9.19 loaded
[ÂÂÂ 6.041167] bttv: using 8 buffers with 2080k (520 pages) each for capture
[ÂÂÂ 6.041559] bttv: Bt8xx card found (0)
[ÂÂÂ 6.041609] bttv: 0: Bt878 (rev 17) at 1000:04:05.0, irq: 19, latency: 128, mmio: 0xc20001000
[ÂÂÂ 6.041622] bttv: 0: using: Typhoon TView RDS + FM Stereo / KNC1 TV Station RDS [card=53,insmod option]
[ÂÂÂ 6.042216] bttv: 0: tuner type=5
[ÂÂÂ 6.111994] bttv: 0: audio absent, no audio device found!
[ÂÂÂ 6.176425] bttv: 0: Setting PLL: 28636363 => 35468950 (needs up to 100ms)
[ÂÂÂ 6.200005] bttv: PLL set ok
[ÂÂÂ 6.209351] bttv: 0: registered device video0
[ÂÂÂ 6.211576] bttv: 0: registered device vbi0
[ÂÂÂ 6.214897] bttv: 0: registered device radio0
[Â 114.218806] bttv 1000:04:05.0: overflow 0x00000000ff507000+4096 of DMA mask ffffffff bus mask df000000
[Â 114.218848] Modules linked in: rfcomm bnep tuner_simple tuner_types tea5767 tuner tda7432 tvaudio msp3400 bttv tea575x tveeprom videobuf_dma_sg videobuf_core rc_core videodev mc btusb btrtl btbcm btintel bluetooth uio_pdrv_genirq uio ecdh_generic ecc
[Â 114.219012] [c0000001ecddf720] [80000000008ff6e8] .buffer_prepare+0x150/0x268 [bttv]
[Â 114.219029] [c0000001ecddf860] [80000000008fff6c] .bttv_qbuf+0x50/0x64 [bttv]

-----

Trace:

[Â 462.783184] Call Trace:
[Â 462.783187] [c0000001c6c67420] [c0000000000b3358] .report_addr+0xb8/0xc0 (unreliable)
[Â 462.783192] [c0000001c6c67490] [c0000000000b351c] .dma_direct_map_page+0xf0/0x128
[Â 462.783195] [c0000001c6c67530] [c0000000000b35b0] .dma_direct_map_sg+0x5c/0xac
[Â 462.783205] [c0000001c6c675e0] [8000000000862e88] .__videobuf_iolock+0x660/0x6d8 [videobuf_dma_sg]
[Â 462.783220] [c0000001c6c676b0] [8000000000854274] .videobuf_iolock+0x98/0xb4 [videobuf_core]
[Â 462.783271] [c0000001c6c67720] [80000000008686e8] .buffer_prepare+0x150/0x268 [bttv]
[Â 462.783276] [c0000001c6c677c0] [8000000000854afc] .videobuf_qbuf+0x2b8/0x428 [videobuf_core]
[Â 462.783288] [c0000001c6c67860] [8000000000868f6c] .bttv_qbuf+0x50/0x64 [bttv]
[Â 462.783383] [c0000001c6c678e0] [80000000007bf208] .v4l_qbuf+0x54/0x60 [videodev]
[Â 462.783402] [c0000001c6c67970] [80000000007c1eac] .__video_do_ioctl+0x30c/0x3f8 [videodev]
[Â 462.783421] [c0000001c6c67a80] [80000000007c3c08] .video_usercopy+0x18c/0x3dc [videodev]
[Â 462.783440] [c0000001c6c67c00] [80000000007bb14c] .v4l2_ioctl+0x60/0x78 [videodev]
[Â 462.783460] [c0000001c6c67c90] [80000000007d3c48] .v4l2_compat_ioctl32+0x9b4/0x1850 [videodev]
[Â 462.783468] [c0000001c6c67d70] [c0000000001ad9cc] .__se_compat_sys_ioctl+0x284/0x127c
[Â 462.783473] [c0000001c6c67e20] [c00000000000067c] system_call+0x60/0x6c
[Â 462.783475] Instruction dump:
[Â 462.783477] 40fe0044 60000000 892255d0 2f890000 40fe0020 3c82ffc5 39200001 60000000
[Â 462.783483] 38842029 992255d0 485ad0d9 60000000 <0fe00000> 38210070 e8010010 7c0803a6
[Â 462.783490] ---[ end trace b677d4a00458e277 ]---

-----

dmesg fsl p5040: https://bugzilla.kernel.org/attachment.cgi?id=285813

Kernel 5.4-rc6 config for the Cyrus+ board and for the QEMU ppce500 board (CPU: P5040 and P5020): https://bugzilla.kernel.org/attachment.cgi?id=285815

Bug report: https://bugzilla.kernel.org/show_bug.cgi?id=205201

Thanks for your help,

Christian