[PATCH v4 0/2] fix dma_addressing_limited() if dma_range_map

[PATCH v4 0/2] fix dma_addressing_limited() if dma_range_map

[Jia He]

This is to fix the hangs at boot. The root cause is the nvme device dma
mapping is failed in the checking path of phys_to_dma() since
dma_max_mapping_size() gave the wrong answer to start with.

---
Changelog:
v1: https://lore.kernel.org/all/20230912084002.2168-1-justin.he@arm.com/
v2:
https://lore.kernel.org/lkml/20231010020835.3678-1-justin.he@arm.com/
  - refine the subject and commit msg (By Robin Murphy)
  - refactor the checking loop in check_ram_in_range_map() in the pages
    unit to avoid wrap to 0 on 32bits platforms (Robin)
v3:
https://lore.kernel.org/lkml/20231016125254.1875-1-justin.he@arm.com/
  - move and export dma_addressing_limited() to avoid adding a new
    exported helper (by Christoph Hellwig)
v4:
  - refine the commit msg in patch01
  - address patch02 coding style issues
  - add the dma ops check in dma_addressing_limited() (Christoph) 
  - move dma_direct_all_ram_mapped() to direct.c (Christoph)

Jia He (2):
  dma-mapping: move dma_addressing_limited() out of line
  dma-mapping: fix dma_addressing_limited() if dma_range_map can't cover
    all system RAM

 include/linux/dma-mapping.h | 19 +++++------------
 kernel/dma/direct.c         | 41 +++++++++++++++++++++++++++++++++++++
 kernel/dma/direct.h         |  1 +
 kernel/dma/mapping.c        | 23 +++++++++++++++++++++
 4 files changed, 70 insertions(+), 14 deletions(-)

-- 
2.25.1

[PATCH v4 1/2] dma-mapping: move dma_addressing_limited() out of line

[Jia He]

This patch moves dma_addressing_limited() out of line, serving as a
preliminary step to prevent the introduction of a new publicly accessible
low-level helper when validating whether all system RAM is mapped within
the DMA mapping range.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jia He <justin.he@arm.com>
---
 include/linux/dma-mapping.h | 19 +++++--------------
 kernel/dma/mapping.c        | 15 +++++++++++++++
 2 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f0ccca16a0ac..4a658de44ee9 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 dma_addressing_limited(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);
@@ -264,6 +265,10 @@ static inline u64 dma_get_required_mask(struct device *dev)
 {
 	return 0;
 }
+static inline bool dma_addressing_limited(struct device *dev)
+{
+	return false;
+}
 static inline size_t dma_max_mapping_size(struct device *dev)
 {
 	return 0;
@@ -465,20 +470,6 @@ static inline int dma_coerce_mask_and_coherent(struct device *dev, u64 mask)
 	return dma_set_mask_and_coherent(dev, mask);
 }
 
-/**
- * dma_addressing_limited - return if the device is addressing limited
- * @dev:	device to check
- *
- * Return %true if the devices DMA mask is too small to address all memory in
- * the system, else %false.  Lack of addressing bits is the prime reason for
- * bounce buffering, but might not be the only one.
- */
-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);
-}
-
 static inline unsigned int dma_get_max_seg_size(struct device *dev)
 {
 	if (dev->dma_parms && dev->dma_parms->max_segment_size)
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index e323ca48f7f2..5bfe782f9a7f 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -793,6 +793,21 @@ int dma_set_coherent_mask(struct device *dev, u64 mask)
 }
 EXPORT_SYMBOL(dma_set_coherent_mask);
 
+/**
+ * dma_addressing_limited - return if the device is addressing limited
+ * @dev:	device to check
+ *
+ * Return %true if the devices DMA mask is too small to address all memory in
+ * the system, else %false.  Lack of addressing bits is the prime reason for
+ * bounce buffering, but might not be the only one.
+ */
+bool dma_addressing_limited(struct device *dev)
+{
+	return min_not_zero(dma_get_mask(dev), dev->bus_dma_limit) <
+			    dma_get_required_mask(dev);
+}
+EXPORT_SYMBOL(dma_addressing_limited);
+
 size_t dma_max_mapping_size(struct device *dev)
 {
 	const struct dma_map_ops *ops = get_dma_ops(dev);
-- 
2.25.1

Re: [PATCH v4 1/2] dma-mapping: move dma_addressing_limited() out of line

[Christoph Hellwig]

> +bool dma_addressing_limited(struct device *dev)
> +{
> +	return min_not_zero(dma_get_mask(dev), dev->bus_dma_limit) <
> +			    dma_get_required_mask(dev);
> +}
> +EXPORT_SYMBOL(dma_addressing_limited);

I've changed this to an EXPORT_SYMBOL_GPL to match dma_get_required_mask.

[PATCH v4 2/2] dma-mapping: fix dma_addressing_limited() if dma_range_map can't cover all system RAM

[Jia He]

There is an unusual case that the range map covers right up to the top
of system RAM, but leaves a hole somewhere lower down. Then it prevents
the nvme device dma mapping in the checking path of phys_to_dma() and
causes the hangs at boot.

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.

Fix 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@arm.com>
---
 kernel/dma/direct.c  | 41 +++++++++++++++++++++++++++++++++++++++++
 kernel/dma/direct.h  |  1 +
 kernel/dma/mapping.c | 12 ++++++++++--
 3 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 9596ae1aa0da..76cc6daa3ffd 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -598,6 +598,47 @@ int dma_direct_supported(struct device *dev, u64 mask)
 	return mask >= phys_to_dma_unencrypted(dev, min_mask);
 }
 
+/*
+ * To check whether all ram resource ranges are covered by dma range map
+ * Returns 0 when further check is needed
+ * Returns 1 if there is some RAM range can't be covered by dma_range_map
+ */
+static int check_ram_in_range_map(unsigned long start_pfn,
+				  unsigned long nr_pages, void *data)
+{
+	unsigned long end_pfn = start_pfn + nr_pages;
+	const struct bus_dma_region *bdr = NULL;
+	const struct bus_dma_region *m;
+	struct device *dev = data;
+
+	while (start_pfn < end_pfn) {
+		for (m = dev->dma_range_map; PFN_DOWN(m->size); m++) {
+			unsigned long cpu_start_pfn = PFN_DOWN(m->cpu_start);
+
+			if (start_pfn >= cpu_start_pfn &&
+			    start_pfn - cpu_start_pfn < PFN_DOWN(m->size)) {
+				bdr = m;
+				break;
+			}
+		}
+		if (!bdr)
+			return 1;
+
+		start_pfn = PFN_DOWN(bdr->cpu_start) + PFN_DOWN(bdr->size);
+	}
+
+	return 0;
+}
+
+bool dma_direct_all_ram_mapped(struct device *dev)
+{
+	if (!dev->dma_range_map)
+		return true;
+
+	return !walk_system_ram_range(0, PFN_DOWN(ULONG_MAX) + 1, dev,
+				      check_ram_in_range_map);
+}
+
 size_t dma_direct_max_mapping_size(struct device *dev)
 {
 	/* If SWIOTLB is active, use its maximum mapping size */
diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h
index 97ec892ea0b5..18d346118fe8 100644
--- a/kernel/dma/direct.h
+++ b/kernel/dma/direct.h
@@ -20,6 +20,7 @@ int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
 bool dma_direct_need_sync(struct device *dev, dma_addr_t dma_addr);
 int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents,
 		enum dma_data_direction dir, unsigned long attrs);
+bool dma_direct_all_ram_mapped(struct device *dev);
 size_t dma_direct_max_mapping_size(struct device *dev);
 
 #if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 5bfe782f9a7f..26eaaf4ac996 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -803,8 +803,16 @@ EXPORT_SYMBOL(dma_set_coherent_mask);
  */
 bool dma_addressing_limited(struct device *dev)
 {
-	return min_not_zero(dma_get_mask(dev), dev->bus_dma_limit) <
-			    dma_get_required_mask(dev);
+	const struct dma_map_ops *ops = get_dma_ops(dev);
+
+	if (min_not_zero(dma_get_mask(dev), dev->bus_dma_limit) <
+			 dma_get_required_mask(dev))
+		return true;
+
+	if (likely(!ops))
+		return !dma_direct_all_ram_mapped(dev);
+
+	return false;
 }
 EXPORT_SYMBOL(dma_addressing_limited);
 
-- 
2.25.1

Re: [PATCH v4 2/2] dma-mapping: fix dma_addressing_limited() if dma_range_map can't cover all system RAM

[Christoph Hellwig]

On Sat, Oct 28, 2023 at 10:20:59AM +0000, Jia He wrote:
> +	if (likely(!ops))
> +		return !dma_direct_all_ram_mapped(dev);
> +
> +	return false;

I've turned his around to make it read a little nicer.

Re: [PATCH v4 0/2] fix dma_addressing_limited() if dma_range_map

[Christoph Hellwig]

Thanks,

this looks good to me, and I've applied this with two tweaks to the
dma-apping tree.

RE: [PATCH v4 0/2] fix dma_addressing_limited() if dma_range_map

[Justin He]

Hi Christoph,

> -----Original Message-----
> Thanks,
> 
> this looks good to me, and I've applied this with two tweaks to the dma-apping
> tree.
Thanks a lot for the help 😊