Subject: [Bug 205201] Booting halts if Dawicontrol DC-2976 UW SCSI board installed, unless RAM size limited to 3500M

From: [email-masked]
Date: Wed, 06 Nov 2019 19:36:15 +0000

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

--- Comment #6 from Christian Zigotzky ([email-masked]) ---
FYI because of the issue with some PCI cards (SCSI, TV cards etc):

Christoph Hellwig wrote:
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 <[email-masked]>
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 <[email-masked]>
---
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);
}

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