Re: [PATCH v2] dma-mapping: treat dev->bus_dma_mask as a DMA limit

From: Robin Murphy
Date: Thu Nov 21 2019 - 12:08:03 EST

On 21/11/2019 9:26 am, Nicolas Saenz Julienne wrote:
Using a mask to represent bus DMA constraints has a set of limitations.
The biggest one being it can only hold a power of two (minus one). The
DMA mapping code is already aware of this and treats dev->bus_dma_mask
as a limit. This quirk is already used by some architectures although
still rare.

With the introduction of the Raspberry Pi 4 we've found a new contender
for the use of bus DMA limits, as its PCIe bus can only address the
lower 3GB of memory (of a total of 4GB). This is impossible to represent
with a mask. To make things worse the device-tree code rounds non power
of two bus DMA limits to the next power of two, which is unacceptable in
this case.

In the light of this, rename dev->bus_dma_mask to dev->bus_dma_limit all
over the tree and treat it as such. Note that dev->bus_dma_limit should
contain the higher accesible DMA address.

^^ super-nit only because I can't not see my editor currently highlighting the typo: "accessible"

Regardless of that though,

Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>

---

Changes since v1:
- rework ACPI code to avoid divergence with OF's

arch/mips/pci/fixup-sb1250.c | 16 ++++++++--------
arch/powerpc/sysdev/fsl_pci.c | 6 +++---
arch/x86/kernel/pci-dma.c | 2 +-
arch/x86/mm/mem_encrypt.c | 2 +-
arch/x86/pci/sta2x11-fixup.c | 2 +-
drivers/acpi/arm64/iort.c | 20 +++++++-------------
drivers/ata/ahci.c | 2 +-
drivers/iommu/dma-iommu.c | 3 +--
drivers/of/device.c | 9 +++++----
include/linux/device.h | 6 +++---
include/linux/dma-direct.h | 2 +-
include/linux/dma-mapping.h | 2 +-
kernel/dma/direct.c | 27 +++++++++++++--------------
13 files changed, 46 insertions(+), 53 deletions(-)

diff --git a/arch/mips/pci/fixup-sb1250.c b/arch/mips/pci/fixup-sb1250.c
index 8a41b359cf90..40efc990cdce 100644
--- a/arch/mips/pci/fixup-sb1250.c
+++ b/arch/mips/pci/fixup-sb1250.c
@@ -21,22 +21,22 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_SIBYTE, PCI_DEVICE_ID_BCM1250_PCI,
/*
* The BCM1250, etc. PCI host bridge does not support DAC on its 32-bit
- * bus, so we set the bus's DMA mask accordingly. However the HT link
+ * bus, so we set the bus's DMA limit accordingly. However the HT link
* down the artificial PCI-HT bridge supports 40-bit addressing and the
* SP1011 HT-PCI bridge downstream supports both DAC and a 64-bit bus
* width, so we record the PCI-HT bridge's secondary and subordinate bus
- * numbers and do not set the mask for devices present in the inclusive
+ * numbers and do not set the limit for devices present in the inclusive
* range of those.
*/
-struct sb1250_bus_dma_mask_exclude {
+struct sb1250_bus_dma_limit_exclude {
bool set;
unsigned char start;
unsigned char end;
};
-static int sb1250_bus_dma_mask(struct pci_dev *dev, void *data)
+static int sb1250_bus_dma_limit(struct pci_dev *dev, void *data)
{
- struct sb1250_bus_dma_mask_exclude *exclude = data;
+ struct sb1250_bus_dma_limit_exclude *exclude = data;
bool exclude_this;
bool ht_bridge;
@@ -55,7 +55,7 @@ static int sb1250_bus_dma_mask(struct pci_dev *dev, void *data)
exclude->start, exclude->end);
} else {
dev_dbg(&dev->dev, "disabling DAC for device");
- dev->dev.bus_dma_mask = DMA_BIT_MASK(32);
+ dev->dev.bus_dma_limit = DMA_BIT_MASK(32);
}
return 0;
@@ -63,9 +63,9 @@ static int sb1250_bus_dma_mask(struct pci_dev *dev, void *data)
static void quirk_sb1250_pci_dac(struct pci_dev *dev)
{
- struct sb1250_bus_dma_mask_exclude exclude = { .set = false };
+ struct sb1250_bus_dma_limit_exclude exclude = { .set = false };
- pci_walk_bus(dev->bus, sb1250_bus_dma_mask, &exclude);
+ pci_walk_bus(dev->bus, sb1250_bus_dma_limit, &exclude);
}
DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_SIBYTE, PCI_DEVICE_ID_BCM1250_PCI,
quirk_sb1250_pci_dac);
diff --git a/arch/powerpc/sysdev/fsl_pci.c b/arch/powerpc/sysdev/fsl_pci.c
index ff0e2b156cb5..617a443d673d 100644
--- a/arch/powerpc/sysdev/fsl_pci.c
+++ b/arch/powerpc/sysdev/fsl_pci.c
@@ -115,8 +115,8 @@ static void pci_dma_dev_setup_swiotlb(struct pci_dev *pdev)
{
struct pci_controller *hose = pci_bus_to_host(pdev->bus);
- pdev->dev.bus_dma_mask =
- hose->dma_window_base_cur + hose->dma_window_size;
+ pdev->dev.bus_dma_limit =
+ hose->dma_window_base_cur + hose->dma_window_size - 1;
}
static void setup_swiotlb_ops(struct pci_controller *hose)
@@ -135,7 +135,7 @@ static void fsl_pci_dma_set_mask(struct device *dev, u64 dma_mask)
* mapping that allows addressing any RAM address from across PCI.
*/
if (dev_is_pci(dev) && dma_mask >= pci64_dma_offset * 2 - 1) {
- dev->bus_dma_mask = 0;
+ dev->bus_dma_limit = 0;
dev->archdata.dma_offset = pci64_dma_offset;
}
}
diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index 57de2ebff7e2..5dcedad21dff 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -140,7 +140,7 @@ rootfs_initcall(pci_iommu_init);
static int via_no_dac_cb(struct pci_dev *pdev, void *data)
{
- pdev->dev.bus_dma_mask = DMA_BIT_MASK(32);
+ pdev->dev.bus_dma_limit = DMA_BIT_MASK(32);
return 0;
}
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 9268c12458c8..a03614bd3e1a 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -367,7 +367,7 @@ bool force_dma_unencrypted(struct device *dev)
if (sme_active()) {
u64 dma_enc_mask = DMA_BIT_MASK(__ffs64(sme_me_mask));
u64 dma_dev_mask = min_not_zero(dev->coherent_dma_mask,
- dev->bus_dma_mask);
+ dev->bus_dma_limit);
if (dma_dev_mask <= dma_enc_mask)
return true;
diff --git a/arch/x86/pci/sta2x11-fixup.c b/arch/x86/pci/sta2x11-fixup.c
index 4a631264b809..c313d784efab 100644
--- a/arch/x86/pci/sta2x11-fixup.c
+++ b/arch/x86/pci/sta2x11-fixup.c
@@ -143,7 +143,7 @@ static void sta2x11_map_ep(struct pci_dev *pdev)
dev->dma_pfn_offset = PFN_DOWN(-amba_base);
- dev->bus_dma_mask = max_amba_addr;
+ dev->bus_dma_limit = max_amba_addr;
pci_set_consistent_dma_mask(pdev, max_amba_addr);
pci_set_dma_mask(pdev, max_amba_addr);
diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
index 5a7551d060f2..33f71983e001 100644
--- a/drivers/acpi/arm64/iort.c
+++ b/drivers/acpi/arm64/iort.c
@@ -1057,8 +1057,8 @@ static int rc_dma_get_range(struct device *dev, u64 *size)
*/
void iort_dma_setup(struct device *dev, u64 *dma_addr, u64 *dma_size)
{
- u64 mask, dmaaddr = 0, size = 0, offset = 0;
- int ret, msb;
+ u64 end, mask, dmaaddr = 0, size = 0, offset = 0;
+ int ret;
/*
* If @dev is expected to be DMA-capable then the bus code that created
@@ -1085,19 +1085,13 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, u64 *dma_size)
}
if (!ret) {
- msb = fls64(dmaaddr + size - 1);
/*
- * Round-up to the power-of-two mask or set
- * the mask to the whole 64-bit address space
- * in case the DMA region covers the full
- * memory window.
+ * Limit coherent and dma mask based on size retrieved from
+ * firmware.
*/
- mask = msb == 64 ? U64_MAX : (1ULL << msb) - 1;
- /*
- * Limit coherent and dma mask based on size
- * retrieved from firmware.
- */
- dev->bus_dma_mask = mask;
+ end = dmaaddr + size - 1;
+ mask = DMA_BIT_MASK(ilog2(end) + 1);
+ dev->bus_dma_limit = end;
dev->coherent_dma_mask = mask;
*dev->dma_mask = mask;
}
diff --git a/drivers/ata/ahci.c b/drivers/ata/ahci.c
index ec6c64fce74a..4bfd1b14b390 100644
--- a/drivers/ata/ahci.c
+++ b/drivers/ata/ahci.c
@@ -910,7 +910,7 @@ static int ahci_configure_dma_masks(struct pci_dev *pdev, int using_dac)
* value, don't extend it here. This happens on STA2X11, for example.
*
* XXX: manipulating the DMA mask from platform code is completely
- * bogus, platform code should use dev->bus_dma_mask instead..
+ * bogus, platform code should use dev->bus_dma_limit instead..
*/
if (pdev->dma_mask && pdev->dma_mask < DMA_BIT_MASK(32))
return 0;
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 041066f3ec99..0cc702a70a96 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -421,8 +421,7 @@ static dma_addr_t iommu_dma_alloc_iova(struct iommu_domain *domain,
if (iova_len < (1 << (IOVA_RANGE_CACHE_MAX_SIZE - 1)))
iova_len = roundup_pow_of_two(iova_len);
- if (dev->bus_dma_mask)
- dma_limit &= dev->bus_dma_mask;
+ dma_limit = min_not_zero(dma_limit, dev->bus_dma_limit);
if (domain->geometry.force_aperture)
dma_limit = min(dma_limit, domain->geometry.aperture_end);
diff --git a/drivers/of/device.c b/drivers/of/device.c
index da8158392010..e9127db7b067 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -93,7 +93,7 @@ int of_dma_configure(struct device *dev, struct device_node *np, bool force_dma)
bool coherent;
unsigned long offset;
const struct iommu_ops *iommu;
- u64 mask;
+ u64 mask, end;
ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
if (ret < 0) {
@@ -148,12 +148,13 @@ int of_dma_configure(struct device *dev, struct device_node *np, bool force_dma)
* Limit coherent and dma mask based on size and default mask
* set by the driver.
*/
- mask = DMA_BIT_MASK(ilog2(dma_addr + size - 1) + 1);
+ end = dma_addr + size - 1;
+ mask = DMA_BIT_MASK(ilog2(end) + 1);
dev->coherent_dma_mask &= mask;
*dev->dma_mask &= mask;
- /* ...but only set bus mask if we found valid dma-ranges earlier */
+ /* ...but only set bus limit if we found valid dma-ranges earlier */
if (!ret)
- dev->bus_dma_mask = mask;
+ dev->bus_dma_limit = end;
coherent = of_dma_is_coherent(np);
dev_dbg(dev, "device is%sdma coherent\n",
diff --git a/include/linux/device.h b/include/linux/device.h
index 99af366db50d..dada6b4bd7e0 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1214,8 +1214,8 @@ struct dev_links_info {
* @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all
* hardware supports 64-bit addresses for consistent allocations
* such descriptors.
- * @bus_dma_mask: Mask of an upstream bridge or bus which imposes a smaller DMA
- * limit than the device itself supports.
+ * @bus_dma_limit: Limit of an upstream bridge or bus which imposes a smaller
+ * DMA limit than the device itself supports.
* @dma_pfn_offset: offset of DMA memory range relatively of RAM
* @dma_parms: A low level driver may set these to teach IOMMU code about
* segment limitations.
@@ -1301,7 +1301,7 @@ struct device {
not all hardware supports
64 bit addresses for consistent
allocations such descriptors. */
- u64 bus_dma_mask; /* upstream dma_mask constraint */
+ u64 bus_dma_limit; /* upstream dma constraint */
unsigned long dma_pfn_offset;
struct device_dma_parameters *dma_parms;
diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index c5c5b5ff2371..aa031cb213c3 100644
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -62,7 +62,7 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size)
min(addr, end) < phys_to_dma(dev, PFN_PHYS(min_low_pfn)))
return false;
- return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_mask);
+ return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_limit);
}
u64 dma_direct_get_required_mask(struct device *dev);
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index a4930310d0c7..330ad58fbf4d 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -694,7 +694,7 @@ 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_mask) <
+ return min_not_zero(dma_get_mask(dev), dev->bus_dma_limit) <
dma_get_required_mask(dev);
}
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 84cf8be65078..998d48ddfb07 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -27,10 +27,10 @@ static void report_addr(struct device *dev, dma_addr_t dma_addr, size_t size)
{
if (!dev->dma_mask) {
dev_err_once(dev, "DMA map on device without dma_mask\n");
- } else if (*dev->dma_mask >= DMA_BIT_MASK(32) || dev->bus_dma_mask) {
+ } else if (*dev->dma_mask >= DMA_BIT_MASK(32) || dev->bus_dma_limit) {
dev_err_once(dev,
- "overflow %pad+%zu of DMA mask %llx bus mask %llx\n",
- &dma_addr, size, *dev->dma_mask, dev->bus_dma_mask);
+ "overflow %pad+%zu of DMA mask %llx bus limit %llx\n",
+ &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
}
WARN_ON_ONCE(1);
}
@@ -57,15 +57,14 @@ u64 dma_direct_get_required_mask(struct device *dev)
}
static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
- u64 *phys_mask)
+ u64 *phys_limit)
{
- if (dev->bus_dma_mask && dev->bus_dma_mask < dma_mask)
- dma_mask = dev->bus_dma_mask;
+ u64 dma_limit = min_not_zero(dma_mask, dev->bus_dma_limit);
if (force_dma_unencrypted(dev))
- *phys_mask = __dma_to_phys(dev, dma_mask);
+ *phys_limit = __dma_to_phys(dev, dma_limit);
else
- *phys_mask = dma_to_phys(dev, dma_mask);
+ *phys_limit = dma_to_phys(dev, dma_limit);
/*
* Optimistically try the zone that the physical address mask falls
@@ -75,9 +74,9 @@ static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
* Note that GFP_DMA32 and GFP_DMA are no ops without the corresponding
* zones.
*/
- if (*phys_mask <= DMA_BIT_MASK(zone_dma_bits))
+ if (*phys_limit <= DMA_BIT_MASK(zone_dma_bits))
return GFP_DMA;
- if (*phys_mask <= DMA_BIT_MASK(32))
+ if (*phys_limit <= DMA_BIT_MASK(32))
return GFP_DMA32;
return 0;
}
@@ -85,7 +84,7 @@ static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
{
return phys_to_dma_direct(dev, phys) + size - 1 <=
- min_not_zero(dev->coherent_dma_mask, dev->bus_dma_mask);
+ min_not_zero(dev->coherent_dma_mask, dev->bus_dma_limit);
}
struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
@@ -94,7 +93,7 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
size_t alloc_size = PAGE_ALIGN(size);
int node = dev_to_node(dev);
struct page *page = NULL;
- u64 phys_mask;
+ u64 phys_limit;
if (attrs & DMA_ATTR_NO_WARN)
gfp |= __GFP_NOWARN;
@@ -102,7 +101,7 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
/* we always manually zero the memory once we are done: */
gfp &= ~__GFP_ZERO;
gfp |= __dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
- &phys_mask);
+ &phys_limit);
page = dma_alloc_contiguous(dev, alloc_size, gfp);
if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
dma_free_contiguous(dev, page, alloc_size);
@@ -116,7 +115,7 @@ struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
page = NULL;
if (IS_ENABLED(CONFIG_ZONE_DMA32) &&
- phys_mask < DMA_BIT_MASK(64) &&
+ phys_limit < DMA_BIT_MASK(64) &&
!(gfp & (GFP_DMA32 | GFP_DMA))) {
gfp |= GFP_DMA32;
goto again;