Re: [PATCH v1] riscv: make ZONE_DMA32 optional

[Vladimir Kondratiev]

It is not necessary any RISCV platform has ZONE_DMA32.
Platforms that not support ZONE_DMA32 should set
CONFIG_NONPORTABLE because lack of ZONE_DMA32
makes such platform non-portable indeed

Example - if platform has no DRAM in [0..4G] region,
it will report failure like below each boot.

[    0.088709] swapper/0: page allocation failure: order:7, mode:0xcc4(GFP_KERNEL|GFP_DMA32), nodemask=(null),cpuset=/
[    0.088832] CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.11.0-rc5 #30
[    0.088864] Call Trace:
[    0.088869] [<ffffffff800059f2>] dump_backtrace+0x1c/0x24
[    0.088910] [<ffffffff805f328c>] show_stack+0x2c/0x38
[    0.088957] [<ffffffff805fd800>] dump_stack_lvl+0x52/0x74
[    0.088987] [<ffffffff805fd836>] dump_stack+0x14/0x1c
[    0.089010] [<ffffffff801a23a8>] warn_alloc+0xf4/0x176
[    0.089041] [<ffffffff801a3052>] __alloc_pages_noprof+0xc28/0xcb4
[    0.089067] [<ffffffff80086eda>] atomic_pool_expand+0x62/0x1f8
[    0.089090] [<ffffffff8080d674>] __dma_atomic_pool_init+0x46/0x9e
[    0.089115] [<ffffffff8080d762>] dma_atomic_pool_init+0x96/0x11c
[    0.089139] [<ffffffff80002146>] do_one_initcall+0x5c/0x1b2
[    0.089158] [<ffffffff8080127c>] kernel_init_freeable+0x214/0x274
[    0.089190] [<ffffffff805fefd8>] kernel_init+0x1e/0x10a
[    0.089209] [<ffffffff8060748a>] ret_from_fork+0xe/0x1c

Signed-off-by: Vladimir Kondratiev <vladimir.kondratiev@xxxxxxxxxxxx>
---
 arch/riscv/Kconfig | 3 ++-
 mm/Kconfig         | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 0f37596a7707..417c6051b679 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -51,6 +51,7 @@ config RISCV
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST
 	select ARCH_HAS_UBSAN
 	select ARCH_HAS_VDSO_DATA
+	select ARCH_HAS_ZONE_DMA_SET if 64BIT && NONPORTABLE
 	select ARCH_KEEP_MEMBLOCK if ACPI
 	select ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE	if 64BIT && MMU
 	select ARCH_OPTIONAL_KERNEL_RWX if ARCH_HAS_STRICT_KERNEL_RWX
@@ -208,7 +209,7 @@ config RISCV
 	select TRACE_IRQFLAGS_SUPPORT
 	select UACCESS_MEMCPY if !MMU
 	select USER_STACKTRACE_SUPPORT
-	select ZONE_DMA32 if 64BIT
+	select ZONE_DMA32 if 64BIT && !NONPORTABLE
 
 config RUSTC_SUPPORTS_RISCV
 	def_bool y
diff --git a/mm/Kconfig b/mm/Kconfig
index 4c9f5ea13271..f96f812193a4 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -1057,7 +1057,7 @@ config ZONE_DMA
 config ZONE_DMA32
 	bool "Support DMA32 zone" if ARCH_HAS_ZONE_DMA_SET
 	depends on !X86_32
-	default y if ARM64
+	default y if ARM64 || (RISCV && 64BIT)
 
 config ZONE_DEVICE
 	bool "Device memory (pmem, HMM, etc...) hotplug support"
-- 
2.43.0