[PATCH v2 0/4] Assorted fixes for RV32

[PATCH v2 0/4] Assorted fixes for RV32

[Atish Patra]

This series fixes various issues observed in latest kernel on RV32.
The first two patches fixes an resource tree introduced in 5.11-rc1
while the last two fixes the case where 2GB physical memory is used
on RV32.

There are may be better way to fix the issue pointed out in PATCH 3
as it seems a generic kernel issue where kernel pointers can not use
last 4k of addressable memory. I am open to other better alternate
suggestions.

Changes from v1->v2:
1. Added Reviewed/Tested by tags.
2. Replaced PHYS_ADDR_MAX with explicit __pa(~(ulong)0).

Atish Patra (4):
RISC-V: Do not allocate memblock while iterating reserved memblocks
RISC-V: Set current memblock limit
RISC-V: Fix L1_CACHE_BYTES for RV32
RISC-V: Fix maximum allowed phsyical memory for RV32

arch/riscv/Kconfig             |  6 ++++--
arch/riscv/include/asm/cache.h |  4 ++++
arch/riscv/kernel/setup.c      | 24 +++++++++++++-----------
arch/riscv/mm/init.c           | 16 ++++++++++++++--
4 files changed, 35 insertions(+), 15 deletions(-)

--
2.25.1


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[PATCH v2 1/4] RISC-V: Do not allocate memblock while iterating reserved memblocks

[Atish Patra]

Currently, resource tree allocates memory blocks while iterating on the
list. It leads to following kernel warning because memblock allocation
also invokes memory block reservation API.

[    0.000000] ------------[ cut here ]------------
[    0.000000] WARNING: CPU: 0 PID: 0 at kernel/resource.c:795
__insert_resource+0x8e/0xd0
[    0.000000] Modules linked in:
[    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted
5.10.0-00022-ge20097fb37e2-dirty #549
[    0.000000] epc: c00125c2 ra : c001262c sp : c1c01f50
[    0.000000]  gp : c1d456e0 tp : c1c0a980 t0 : ffffcf20
[    0.000000]  t1 : 00000000 t2 : 00000000 s0 : c1c01f60
[    0.000000]  s1 : ffffcf00 a0 : ffffff00 a1 : c1c0c0c4
[    0.000000]  a2 : 80c12b15 a3 : 80402000 a4 : 80402000
[    0.000000]  a5 : c1c0c0c4 a6 : 80c12b15 a7 : f5faf600
[    0.000000]  s2 : c1c0c0c4 s3 : c1c0e000 s4 : c1009a80
[    0.000000]  s5 : c1c0c000 s6 : c1d48000 s7 : c1613b4c
[    0.000000]  s8 : 00000fff s9 : 80000200 s10: c1613b40
[    0.000000]  s11: 00000000 t3 : c1d4a000 t4 : ffffffff

This is also unnecessary as we can pre-compute the total memblocks required
for each memory region and allocate it before the loop. It save precious
boot time not going through memblock allocation code every time.

Fixes: 00ab027a3b82 ("RISC-V: Add kernel image sections to the resource tree")

Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/kernel/setup.c | 24 +++++++++++++-----------
 1 file changed, 13 insertions(+), 11 deletions(-)

diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index 1d85e9bf783c..3fa3f26dde85 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -127,7 +127,9 @@ static void __init init_resources(void)
 {
 	struct memblock_region *region = NULL;
 	struct resource *res = NULL;
-	int ret = 0;
+	struct resource *mem_res = NULL;
+	size_t mem_res_sz = 0;
+	int ret = 0, i = 0;
 
 	code_res.start = __pa_symbol(_text);
 	code_res.end = __pa_symbol(_etext) - 1;
@@ -145,16 +147,17 @@ static void __init init_resources(void)
 	bss_res.end = __pa_symbol(__bss_stop) - 1;
 	bss_res.flags = IORESOURCE_SYSTEM_RAM | IORESOURCE_BUSY;
 
+	mem_res_sz = (memblock.memory.cnt + memblock.reserved.cnt) * sizeof(*mem_res);
+	mem_res = memblock_alloc(mem_res_sz, SMP_CACHE_BYTES);
+	if (!mem_res)
+		panic("%s: Failed to allocate %zu bytes\n", __func__, mem_res_sz);
 	/*
 	 * Start by adding the reserved regions, if they overlap
 	 * with /memory regions, insert_resource later on will take
 	 * care of it.
 	 */
 	for_each_reserved_mem_region(region) {
-		res = memblock_alloc(sizeof(struct resource), SMP_CACHE_BYTES);
-		if (!res)
-			panic("%s: Failed to allocate %zu bytes\n", __func__,
-			      sizeof(struct resource));
+		res = &mem_res[i++];
 
 		res->name = "Reserved";
 		res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
@@ -171,8 +174,10 @@ static void __init init_resources(void)
 		 * Ignore any other reserved regions within
 		 * system memory.
 		 */
-		if (memblock_is_memory(res->start))
+		if (memblock_is_memory(res->start)) {
+			memblock_free((phys_addr_t) res, sizeof(struct resource));
 			continue;
+		}
 
 		ret = add_resource(&iomem_resource, res);
 		if (ret < 0)
@@ -181,10 +186,7 @@ static void __init init_resources(void)
 
 	/* Add /memory regions to the resource tree */
 	for_each_mem_region(region) {
-		res = memblock_alloc(sizeof(struct resource), SMP_CACHE_BYTES);
-		if (!res)
-			panic("%s: Failed to allocate %zu bytes\n", __func__,
-			      sizeof(struct resource));
+		res = &mem_res[i++];
 
 		if (unlikely(memblock_is_nomap(region))) {
 			res->name = "Reserved";
@@ -205,9 +207,9 @@ static void __init init_resources(void)
 	return;
 
  error:
-	memblock_free((phys_addr_t) res, sizeof(struct resource));
 	/* Better an empty resource tree than an inconsistent one */
 	release_child_resources(&iomem_resource);
+	memblock_free((phys_addr_t) mem_res, mem_res_sz);
 }
 
 
-- 
2.25.1


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[PATCH v2 2/4] RISC-V: Set current memblock limit

[Atish Patra]

Currently, linux kernel can not use last 4k bytes of addressable space
because IS_ERR_VALUE macro treats those as an error. This will be an issue
for RV32 as any memblock allocator potentially allocate chunk of memory
from the end of DRAM (2GB) leading bad address error even though the
address was technically valid.

Fix this issue by limiting the memblock if available memory spans the
entire address space.

Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/mm/init.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index bf5379135e39..7cd4993f4ff2 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -157,9 +157,10 @@ static void __init setup_initrd(void)
 void __init setup_bootmem(void)
 {
 	phys_addr_t mem_start = 0;
-	phys_addr_t start, end = 0;
+	phys_addr_t start, dram_end, end = 0;
 	phys_addr_t vmlinux_end = __pa_symbol(&_end);
 	phys_addr_t vmlinux_start = __pa_symbol(&_start);
+	phys_addr_t max_mapped_addr = __pa(~(ulong)0);
 	u64 i;
 
 	/* Find the memory region containing the kernel */
@@ -181,7 +182,18 @@ void __init setup_bootmem(void)
 	/* Reserve from the start of the kernel to the end of the kernel */
 	memblock_reserve(vmlinux_start, vmlinux_end - vmlinux_start);
 
-	max_pfn = PFN_DOWN(memblock_end_of_DRAM());
+	dram_end = memblock_end_of_DRAM();
+
+	/*
+	 * memblock allocator is not aware of the fact that last 4K bytes of
+	 * the addressable memory can not be mapped because of IS_ERR_VALUE
+	 * macro. Make sure that last 4k bytes are not usable by memblock
+	 * if end of dram is equal to maximum addressable memory.
+	 */
+	if (max_mapped_addr == (dram_end - 1))
+		memblock_set_current_limit(max_mapped_addr - 4096);
+
+	max_pfn = PFN_DOWN(dram_end);
 	max_low_pfn = max_pfn;
 	dma32_phys_limit = min(4UL * SZ_1G, (unsigned long)PFN_PHYS(max_low_pfn));
 	set_max_mapnr(max_low_pfn);
-- 
2.25.1


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[PATCH v2 3/4] RISC-V: Fix L1_CACHE_BYTES for RV32

[Atish Patra]

SMP_CACHE_BYTES/L1_CACHE_BYTES should be defined as 32 instead of
64 for RV32. Otherwise, there will be hole of 32 bytes with each memblock
allocation if it is requested to be aligned with SMP_CACHE_BYTES.

Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
(on vexriscv)
Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/include/asm/cache.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/riscv/include/asm/cache.h b/arch/riscv/include/asm/cache.h
index 9b58b104559e..c9c669ea2fe6 100644
--- a/arch/riscv/include/asm/cache.h
+++ b/arch/riscv/include/asm/cache.h
@@ -7,7 +7,11 @@
 #ifndef _ASM_RISCV_CACHE_H
 #define _ASM_RISCV_CACHE_H
 
+#ifdef CONFIG_64BIT
 #define L1_CACHE_SHIFT		6
+#else
+#define L1_CACHE_SHIFT		5
+#endif
 
 #define L1_CACHE_BYTES		(1 << L1_CACHE_SHIFT)
 
-- 
2.25.1


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[PATCH v2 4/4] RISC-V: Fix maximum allowed phsyical memory for RV32

[Atish Patra]

Linux kernel can only map 1GB of address space for RV32 as the page offset
is set to 0xC0000000. The current description in the Kconfig is confusing
as it indicates that RV32 can support 2GB of physical memory. That is
simply not true for current kernel. In future, a 2GB split support can be
added to allow 2GB physical address space.

Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atish.patra@wdc.com>
---
 arch/riscv/Kconfig | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 81b76d44725d..e9e2c1f0a690 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -137,7 +137,7 @@ config PA_BITS
 
 config PAGE_OFFSET
 	hex
-	default 0xC0000000 if 32BIT && MAXPHYSMEM_2GB
+	default 0xC0000000 if 32BIT && MAXPHYSMEM_1GB
 	default 0x80000000 if 64BIT && !MMU
 	default 0xffffffff80000000 if 64BIT && MAXPHYSMEM_2GB
 	default 0xffffffe000000000 if 64BIT && MAXPHYSMEM_128GB
@@ -247,10 +247,12 @@ config MODULE_SECTIONS
 
 choice
 	prompt "Maximum Physical Memory"
-	default MAXPHYSMEM_2GB if 32BIT
+	default MAXPHYSMEM_1GB if 32BIT
 	default MAXPHYSMEM_2GB if 64BIT && CMODEL_MEDLOW
 	default MAXPHYSMEM_128GB if 64BIT && CMODEL_MEDANY
 
+	config MAXPHYSMEM_1GB
+		bool "1GiB"
 	config MAXPHYSMEM_2GB
 		bool "2GiB"
 	config MAXPHYSMEM_128GB
-- 
2.25.1


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