Re: [PATCH] dma-mapping: fix dma_addressing_limited if dma_range_map is scanned
From: Robin Murphy
Date: Tue Sep 12 2023 - 07:57:45 EST
On 12/09/2023 9:40 am, Jia He wrote:
After scanning the dma_range_map, if it is found that not all of the
system RAM ranges are encompassed within it, an incorrect calculation
occurs for dma_addressing_limited(), which prevents the nvme device
dma mapping in the checking path of phys_to_dma().
Nit: the subject and this description aren't very clear - the key point
here is the unusual case that the range map covers right up to the top
of system RAM, but leaves a hole somewhere lower down. There's no issue
with the more typical case where some RAM exists above the top of the
range map, since bus_dma_limit will capture that and work as expected.
E.g. On an Armv8 Ampere server, the dsdt ACPI table is:
Method (_DMA, 0, Serialized) // _DMA: Direct Memory Access
{
Name (RBUF, ResourceTemplate ()
{
QWordMemory (ResourceConsumer, PosDecode, MinFixed,
MaxFixed, Cacheable, ReadWrite,
0x0000000000000000, // Granularity
0x0000000000000000, // Range Minimum
0x00000000FFFFFFFF, // Range Maximum
0x0000000000000000, // Translation Offset
0x0000000100000000, // Length
,, , AddressRangeMemory, TypeStatic)
QWordMemory (ResourceConsumer, PosDecode, MinFixed,
MaxFixed, Cacheable, ReadWrite,
0x0000000000000000, // Granularity
0x0000006010200000, // Range Minimum
0x000000602FFFFFFF, // Range Maximum
0x0000000000000000, // Translation Offset
0x000000001FE00000, // Length
,, , AddressRangeMemory, TypeStatic)
QWordMemory (ResourceConsumer, PosDecode, MinFixed,
MaxFixed, Cacheable, ReadWrite,
0x0000000000000000, // Granularity
0x00000060F0000000, // Range Minimum
0x00000060FFFFFFFF, // Range Maximum
0x0000000000000000, // Translation Offset
0x0000000010000000, // Length
,, , AddressRangeMemory, TypeStatic)
QWordMemory (ResourceConsumer, PosDecode, MinFixed,
MaxFixed, Cacheable, ReadWrite,
0x0000000000000000, // Granularity
0x0000007000000000, // Range Minimum
0x000003FFFFFFFFFF, // Range Maximum
0x0000000000000000, // Translation Offset
0x0000039000000000, // Length
,, , AddressRangeMemory, TypeStatic)
})
But the System RAM ranges are:
cat /proc/iomem |grep -i ram
90000000-91ffffff : System RAM
92900000-fffbffff : System RAM
880000000-fffffffff : System RAM
8800000000-bff5990fff : System RAM
bff59d0000-bff5a4ffff : System RAM
bff8000000-bfffffffff : System RAM
So some RAM ranges are out of dma_range_map.
Fixes it by checking whether each of the system RAM resources can be
properly encompassed within the dma_range_map.
Signed-off-by: Jia He <justin.he@xxxxxxx>
---
include/linux/dma-mapping.h | 8 +++++--
kernel/dma/mapping.c | 45 +++++++++++++++++++++++++++++++++++++
2 files changed, 51 insertions(+), 2 deletions(-)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f0ccca16a0ac..d9d1c67c8579 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -144,6 +144,7 @@ bool dma_pci_p2pdma_supported(struct device *dev);
int dma_set_mask(struct device *dev, u64 mask);
int dma_set_coherent_mask(struct device *dev, u64 mask);
u64 dma_get_required_mask(struct device *dev);
+bool all_ram_in_dma_range_map(struct device *dev);
size_t dma_max_mapping_size(struct device *dev);
size_t dma_opt_mapping_size(struct device *dev);
bool dma_need_sync(struct device *dev, dma_addr_t dma_addr);
@@ -475,8 +476,11 @@ static inline int dma_coerce_mask_and_coherent(struct device *dev, u64 mask)
*/
static inline bool dma_addressing_limited(struct device *dev)
{
- return min_not_zero(dma_get_mask(dev), dev->bus_dma_limit) <
- dma_get_required_mask(dev);
+ if (min_not_zero(dma_get_mask(dev), dev->bus_dma_limit) <
+ dma_get_required_mask(dev))
Nit: indentation
+ return true;
+
+ return !all_ram_in_dma_range_map(dev);
}
static inline unsigned int dma_get_max_seg_size(struct device *dev)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index e323ca48f7f2..ab407deb81b8 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -14,6 +14,7 @@
#include <linux/of_device.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
+#include <linux/dma-direct.h>
Nit: please keep the includes sorted alphabetically, however I do wonder
whether this whole thing shouldn't belong in dma-direct anyway.
#include "debug.h"
#include "direct.h"
@@ -819,6 +820,50 @@ size_t dma_opt_mapping_size(struct device *dev)
}
EXPORT_SYMBOL_GPL(dma_opt_mapping_size);
+/*
+ * To check whether all ram resource ranges are mapped in dma range map
+ * Returns 0 when continuous check is needed
+ * Returns 1 if there is some ram range can't be mapped to dma_range_map
+ */
+static int check_ram_in_range_map(unsigned long start_pfn,
+ unsigned long nr_pages, void *data)
+{
+ phys_addr_t end_paddr = (start_pfn + nr_pages) << PAGE_SHIFT;
This could still wrap to 0 on 32-bit. I think the robust thing to do is
either spray some extra -1s and +1s around to make all the "end" values
inclusive limits, or maybe just do everything in units of pages rather
than bytes (i.e. use PFN_DOWN() on the bus_dma_region entry values).
+ phys_addr_t start_paddr = start_pfn << PAGE_SHIFT;
+ struct device *dev = (struct device *)data;
+ struct bus_dma_region *region = NULL;
+ const struct bus_dma_region *m;
+
+ while (start_paddr < end_paddr) {
+ // find region containing start_paddr
Nit: inconsistent comment style (although it's not a particularly
valuable comment anyway, IMO the loop itself is clear enough).
Thanks,
Robin.
+ for (m = dev->dma_range_map; m->size; m++) {
+ if (start_paddr >= m->cpu_start
+ && start_paddr - m->cpu_start < m->size) {
+ region = (struct bus_dma_region *)m;
+ break;
+ }
+ }
+ if (!region)
+ return 1;
+
+ start_paddr = region->cpu_start + region->size;
+ /* handle overflow of phys_addr_t */
+ if (start_paddr == 0)
+ break;
+ }
+
+ return 0;
+}
+
+bool all_ram_in_dma_range_map(struct device *dev)
+{
+ if (!dev->dma_range_map)
+ return 1;
+
+ return !walk_system_ram_range(0, ULONG_MAX, dev, check_ram_in_range_map);
+}
+EXPORT_SYMBOL_GPL(all_ram_in_dma_range_map);
+
bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
{
const struct dma_map_ops *ops = get_dma_ops(dev);