| Message ID | 20201021123437.21538-7-nsaenzjulienne@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: Default to 32-bit wide ZONE_DMA | expand |
On Wed, Oct 21, 2020 at 02:34:36PM +0200, Nicolas Saenz Julienne wrote: > From: Ard Biesheuvel <ardb@kernel.org> > > We recently introduced a 1 GB sized ZONE_DMA to cater for platforms > incorporating masters that can address less than 32 bits of DMA, in > particular the Raspberry Pi 4, which has 4 or 8 GB of DRAM, but has > peripherals that can only address up to 1 GB (and its PCIe host > bridge can only access the bottom 3 GB) > > Instructing the DMA layer about these limitations is straight-forward, > even though we had to fix some issues regarding memory limits set in > the IORT for named components, and regarding the handling of ACPI _DMA > methods. However, the DMA layer also needs to be able to allocate > memory that is guaranteed to meet those DMA constraints, for bounce > buffering as well as allocating the backing for consistent mappings. > > This is why the 1 GB ZONE_DMA was introduced recently. Unfortunately, > it turns out the having a 1 GB ZONE_DMA as well as a ZONE_DMA32 causes > problems with kdump, and potentially in other places where allocations > cannot cross zone boundaries. Therefore, we should avoid having two > separate DMA zones when possible. > > So let's do an early scan of the IORT, and only create the ZONE_DMA > if we encounter any devices that need it. This puts the burden on > the firmware to describe such limitations in the IORT, which may be > redundant (and less precise) if _DMA methods are also being provided. > However, it should be noted that this situation is highly unusual for > arm64 ACPI machines. Also, the DMA subsystem still gives precedence to > the _DMA method if implemented, and so we will not lose the ability to > perform streaming DMA outside the ZONE_DMA if the _DMA method permits > it. > > Cc: Jeremy Linton <jeremy.linton@arm.com> > Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> > Cc: Rob Herring <robh+dt@kernel.org> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Robin Murphy <robin.murphy@arm.com> > Cc: Hanjun Guo <guohanjun@huawei.com> > Cc: Sudeep Holla <sudeep.holla@arm.com> > Cc: Anshuman Khandual <anshuman.khandual@arm.com> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > [nsaenz: Rebased, removed documentation change and add declaration in acpi_iort.h] > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> > > --- > > Changes since v3: > - Use min_not_zero() > - Check ACPI revision > - Remove unnecessary #ifdef in zone_sizes_init() > > arch/arm64/mm/init.c | 3 ++- > drivers/acpi/arm64/iort.c | 52 +++++++++++++++++++++++++++++++++++++++ > include/linux/acpi_iort.h | 4 +++ > 3 files changed, 58 insertions(+), 1 deletion(-) Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c > index 94e38f99748b..f5d4f85506e4 100644 > --- a/arch/arm64/mm/init.c > +++ b/arch/arm64/mm/init.c > @@ -29,6 +29,7 @@ > #include <linux/kexec.h> > #include <linux/crash_dump.h> > #include <linux/hugetlb.h> > +#include <linux/acpi_iort.h> > > #include <asm/boot.h> > #include <asm/fixmap.h> > @@ -190,7 +191,7 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max) > > #ifdef CONFIG_ZONE_DMA > dt_zone_dma_bits = ilog2(of_dma_get_max_cpu_address(NULL)); > - zone_dma_bits = min(32U, dt_zone_dma_bits); > + zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_iort_get_zone_dma_size()); > arm64_dma_phys_limit = max_zone_phys(zone_dma_bits); > max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit); > #endif > diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c > index 9929ff50c0c0..05fe4a076bab 100644 > --- a/drivers/acpi/arm64/iort.c > +++ b/drivers/acpi/arm64/iort.c > @@ -1718,3 +1718,55 @@ void __init acpi_iort_init(void) > > iort_init_platform_devices(); > } > + > +#ifdef CONFIG_ZONE_DMA > +/* > + * Check the IORT whether any devices exist whose DMA mask is < 32 bits. > + * If so, return the smallest value encountered, or 32 otherwise. > + */ > +unsigned int __init acpi_iort_get_zone_dma_size(void) > +{ > + struct acpi_table_iort *iort; > + struct acpi_iort_node *node, *end; > + acpi_status status; > + u8 limit = 32; > + int i; > + > + if (acpi_disabled) > + return limit; > + > + status = acpi_get_table(ACPI_SIG_IORT, 0, > + (struct acpi_table_header **)&iort); > + if (ACPI_FAILURE(status)) > + return limit; > + > + node = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->node_offset); > + end = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->header.length); > + > + for (i = 0; i < iort->node_count; i++) { > + if (node >= end) > + break; > + > + switch (node->type) { > + struct acpi_iort_named_component *ncomp; > + struct acpi_iort_root_complex *rc; > + > + case ACPI_IORT_NODE_NAMED_COMPONENT: > + ncomp = (struct acpi_iort_named_component *)node->node_data; > + limit = min_not_zero(limit, ncomp->memory_address_limit); > + break; > + > + case ACPI_IORT_NODE_PCI_ROOT_COMPLEX: > + if (node->revision < 1) > + break; > + > + rc = (struct acpi_iort_root_complex *)node->node_data; > + limit = min_not_zero(limit, rc->memory_address_limit); > + break; > + } > + node = ACPI_ADD_PTR(struct acpi_iort_node, node, node->length); > + } > + acpi_put_table(&iort->header); > + return limit; > +} > +#endif > diff --git a/include/linux/acpi_iort.h b/include/linux/acpi_iort.h > index 20a32120bb88..7d2e184f0d4d 100644 > --- a/include/linux/acpi_iort.h > +++ b/include/linux/acpi_iort.h > @@ -38,6 +38,7 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, u64 *size); > const struct iommu_ops *iort_iommu_configure_id(struct device *dev, > const u32 *id_in); > int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head *head); > +unsigned int acpi_iort_get_zone_dma_size(void); > #else > static inline void acpi_iort_init(void) { } > static inline u32 iort_msi_map_id(struct device *dev, u32 id) > @@ -55,6 +56,9 @@ static inline const struct iommu_ops *iort_iommu_configure_id( > static inline > int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head *head) > { return 0; } > + > +static inline unsigned int acpi_iort_get_zone_dma_size(void) > +{ return 32; } > #endif > > #endif /* __ACPI_IORT_H__ */ > -- > 2.28.0 >
On 2020/10/21 20:34, Nicolas Saenz Julienne wrote: > From: Ard Biesheuvel <ardb@kernel.org> > > We recently introduced a 1 GB sized ZONE_DMA to cater for platforms > incorporating masters that can address less than 32 bits of DMA, in > particular the Raspberry Pi 4, which has 4 or 8 GB of DRAM, but has > peripherals that can only address up to 1 GB (and its PCIe host > bridge can only access the bottom 3 GB) > > Instructing the DMA layer about these limitations is straight-forward, > even though we had to fix some issues regarding memory limits set in > the IORT for named components, and regarding the handling of ACPI _DMA > methods. However, the DMA layer also needs to be able to allocate > memory that is guaranteed to meet those DMA constraints, for bounce > buffering as well as allocating the backing for consistent mappings. > > This is why the 1 GB ZONE_DMA was introduced recently. Unfortunately, > it turns out the having a 1 GB ZONE_DMA as well as a ZONE_DMA32 causes > problems with kdump, and potentially in other places where allocations > cannot cross zone boundaries. Therefore, we should avoid having two > separate DMA zones when possible. > > So let's do an early scan of the IORT, and only create the ZONE_DMA > if we encounter any devices that need it. This puts the burden on > the firmware to describe such limitations in the IORT, which may be > redundant (and less precise) if _DMA methods are also being provided. > However, it should be noted that this situation is highly unusual for > arm64 ACPI machines. Also, the DMA subsystem still gives precedence to > the _DMA method if implemented, and so we will not lose the ability to > perform streaming DMA outside the ZONE_DMA if the _DMA method permits > it. > > Cc: Jeremy Linton <jeremy.linton@arm.com> > Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > Cc: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> > Cc: Rob Herring <robh+dt@kernel.org> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Robin Murphy <robin.murphy@arm.com> > Cc: Hanjun Guo <guohanjun@huawei.com> > Cc: Sudeep Holla <sudeep.holla@arm.com> > Cc: Anshuman Khandual <anshuman.khandual@arm.com> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org> > [nsaenz: Rebased, removed documentation change and add declaration in acpi_iort.h] > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de> > > --- > > Changes since v3: > - Use min_not_zero() > - Check ACPI revision > - Remove unnecessary #ifdef in zone_sizes_init() > > arch/arm64/mm/init.c | 3 ++- > drivers/acpi/arm64/iort.c | 52 +++++++++++++++++++++++++++++++++++++++ > include/linux/acpi_iort.h | 4 +++ Acked-by: Hanjun Guo <guohanjun@huawei.com>
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index 94e38f99748b..f5d4f85506e4 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -29,6 +29,7 @@ #include <linux/kexec.h> #include <linux/crash_dump.h> #include <linux/hugetlb.h> +#include <linux/acpi_iort.h> #include <asm/boot.h> #include <asm/fixmap.h> @@ -190,7 +191,7 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max) #ifdef CONFIG_ZONE_DMA dt_zone_dma_bits = ilog2(of_dma_get_max_cpu_address(NULL)); - zone_dma_bits = min(32U, dt_zone_dma_bits); + zone_dma_bits = min3(32U, dt_zone_dma_bits, acpi_iort_get_zone_dma_size()); arm64_dma_phys_limit = max_zone_phys(zone_dma_bits); max_zone_pfns[ZONE_DMA] = PFN_DOWN(arm64_dma_phys_limit); #endif diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c index 9929ff50c0c0..05fe4a076bab 100644 --- a/drivers/acpi/arm64/iort.c +++ b/drivers/acpi/arm64/iort.c @@ -1718,3 +1718,55 @@ void __init acpi_iort_init(void) iort_init_platform_devices(); } + +#ifdef CONFIG_ZONE_DMA +/* + * Check the IORT whether any devices exist whose DMA mask is < 32 bits. + * If so, return the smallest value encountered, or 32 otherwise. + */ +unsigned int __init acpi_iort_get_zone_dma_size(void) +{ + struct acpi_table_iort *iort; + struct acpi_iort_node *node, *end; + acpi_status status; + u8 limit = 32; + int i; + + if (acpi_disabled) + return limit; + + status = acpi_get_table(ACPI_SIG_IORT, 0, + (struct acpi_table_header **)&iort); + if (ACPI_FAILURE(status)) + return limit; + + node = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->node_offset); + end = ACPI_ADD_PTR(struct acpi_iort_node, iort, iort->header.length); + + for (i = 0; i < iort->node_count; i++) { + if (node >= end) + break; + + switch (node->type) { + struct acpi_iort_named_component *ncomp; + struct acpi_iort_root_complex *rc; + + case ACPI_IORT_NODE_NAMED_COMPONENT: + ncomp = (struct acpi_iort_named_component *)node->node_data; + limit = min_not_zero(limit, ncomp->memory_address_limit); + break; + + case ACPI_IORT_NODE_PCI_ROOT_COMPLEX: + if (node->revision < 1) + break; + + rc = (struct acpi_iort_root_complex *)node->node_data; + limit = min_not_zero(limit, rc->memory_address_limit); + break; + } + node = ACPI_ADD_PTR(struct acpi_iort_node, node, node->length); + } + acpi_put_table(&iort->header); + return limit; +} +#endif diff --git a/include/linux/acpi_iort.h b/include/linux/acpi_iort.h index 20a32120bb88..7d2e184f0d4d 100644 --- a/include/linux/acpi_iort.h +++ b/include/linux/acpi_iort.h @@ -38,6 +38,7 @@ void iort_dma_setup(struct device *dev, u64 *dma_addr, u64 *size); const struct iommu_ops *iort_iommu_configure_id(struct device *dev, const u32 *id_in); int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head *head); +unsigned int acpi_iort_get_zone_dma_size(void); #else static inline void acpi_iort_init(void) { } static inline u32 iort_msi_map_id(struct device *dev, u32 id) @@ -55,6 +56,9 @@ static inline const struct iommu_ops *iort_iommu_configure_id( static inline int iort_iommu_msi_get_resv_regions(struct device *dev, struct list_head *head) { return 0; } + +static inline unsigned int acpi_iort_get_zone_dma_size(void) +{ return 32; } #endif #endif /* __ACPI_IORT_H__ */