arch/riscv/mm/init.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
This commit fixes the alignment of phys_ram_base in RISC-V.
In sparse vmemmap model, the virtual address of vmemmap is calculated as:
'(struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT)'.
And the struct page's va can be calculated with an offset:
'vmemmap + (pfn)'.
However, when initializing struct pages, kernel actually starts from the
first page from the same section that phys_ram_base belongs to. If the
first page's physical address is not 'phys_ram_base >> PAGE_SHIFT', then
we get an va below VMEMMAP_START when calculating va for it's struct page.
For example, if phys_ram_base starts from 0x82000000 with pfn 0x82000, the
first page in the same section is actually pfn 0x80000. During
init_unavailage_range, we will initialize struct page for pfn 0x80000
with virtual address '(struct page *)VMEMMAP_START - 0x2000', which is
below VMEMMAP_START as well as PCI_IO_END.
This commit fixes this bug by aligning phys_ram_base with SECTION_SIZE.
Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
---
arch/riscv/mm/init.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 0e8c20adcd98..9866de267b74 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -59,6 +59,8 @@ EXPORT_SYMBOL(pgtable_l4_enabled);
EXPORT_SYMBOL(pgtable_l5_enabled);
#endif
+#define RISCV_MEMSTART_ALIGN (1UL << SECTION_SIZE_BITS)
+
phys_addr_t phys_ram_base __ro_after_init;
EXPORT_SYMBOL(phys_ram_base);
@@ -241,7 +243,8 @@ static void __init setup_bootmem(void)
* at worst, we map the linear mapping with PMD mappings.
*/
if (!IS_ENABLED(CONFIG_XIP_KERNEL))
- phys_ram_base = memblock_start_of_DRAM() & PMD_MASK;
+ phys_ram_base = round_down(memblock_start_of_DRAM(),
+ RISCV_MEMSTART_ALIGN);
/*
* In 64-bit, any use of __va/__pa before this point is wrong as we
--
2.20.1Xu Lu <luxu.kernel@bytedance.com> writes: > This commit fixes the alignment of phys_ram_base in RISC-V. > > In sparse vmemmap model, the virtual address of vmemmap is calculated as: > '(struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT)'. > And the struct page's va can be calculated with an offset: > 'vmemmap + (pfn)'. > > However, when initializing struct pages, kernel actually starts from the > first page from the same section that phys_ram_base belongs to. If the > first page's physical address is not 'phys_ram_base >> PAGE_SHIFT', then > we get an va below VMEMMAP_START when calculating va for it's struct page. Nice catch! I managed to reproduce this on a hacked qemu virt machine. > For example, if phys_ram_base starts from 0x82000000 with pfn 0x82000, the > first page in the same section is actually pfn 0x80000. During > init_unavailage_range, we will initialize struct page for pfn 0x80000 "init_unavailable_range()" spelling for greppability. > with virtual address '(struct page *)VMEMMAP_START - 0x2000', which is > below VMEMMAP_START as well as PCI_IO_END. > > This commit fixes this bug by aligning phys_ram_base with SECTION_SIZE. > > Signed-off-by: Xu Lu <luxu.kernel@bytedance.com> Please add a fixes tag. > --- > arch/riscv/mm/init.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > index 0e8c20adcd98..9866de267b74 100644 > --- a/arch/riscv/mm/init.c > +++ b/arch/riscv/mm/init.c > @@ -59,6 +59,8 @@ EXPORT_SYMBOL(pgtable_l4_enabled); > EXPORT_SYMBOL(pgtable_l5_enabled); > #endif > > +#define RISCV_MEMSTART_ALIGN (1UL << SECTION_SIZE_BITS) > + > phys_addr_t phys_ram_base __ro_after_init; > EXPORT_SYMBOL(phys_ram_base); > > @@ -241,7 +243,8 @@ static void __init setup_bootmem(void) > * at worst, we map the linear mapping with PMD mappings. > */ > if (!IS_ENABLED(CONFIG_XIP_KERNEL)) > - phys_ram_base = memblock_start_of_DRAM() & PMD_MASK; > + phys_ram_base = round_down(memblock_start_of_DRAM(), > + RISCV_MEMSTART_ALIGN); No need to wrap this line. Also, is the RISCV_MEMSTART_ALIGN define really needed? The kernel test robot had some build issues as well! Björn
On Tue, Dec 3, 2024 at 7:50 PM Björn Töpel <bjorn@kernel.org> wrote: > > Xu Lu <luxu.kernel@bytedance.com> writes: > > > This commit fixes the alignment of phys_ram_base in RISC-V. > > > > In sparse vmemmap model, the virtual address of vmemmap is calculated as: > > '(struct page *)VMEMMAP_START - (phys_ram_base >> PAGE_SHIFT)'. > > And the struct page's va can be calculated with an offset: > > 'vmemmap + (pfn)'. > > > > However, when initializing struct pages, kernel actually starts from the > > first page from the same section that phys_ram_base belongs to. If the > > first page's physical address is not 'phys_ram_base >> PAGE_SHIFT', then > > we get an va below VMEMMAP_START when calculating va for it's struct page. > > Nice catch! I managed to reproduce this on a hacked qemu virt machine. > > > For example, if phys_ram_base starts from 0x82000000 with pfn 0x82000, the > > first page in the same section is actually pfn 0x80000. During > > init_unavailage_range, we will initialize struct page for pfn 0x80000 > > "init_unavailable_range()" spelling for greppability. > > > with virtual address '(struct page *)VMEMMAP_START - 0x2000', which is > > below VMEMMAP_START as well as PCI_IO_END. > > > > This commit fixes this bug by aligning phys_ram_base with SECTION_SIZE. > > > > Signed-off-by: Xu Lu <luxu.kernel@bytedance.com> > > Please add a fixes tag. Roger that. > > > --- > > arch/riscv/mm/init.c | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c > > index 0e8c20adcd98..9866de267b74 100644 > > --- a/arch/riscv/mm/init.c > > +++ b/arch/riscv/mm/init.c > > @@ -59,6 +59,8 @@ EXPORT_SYMBOL(pgtable_l4_enabled); > > EXPORT_SYMBOL(pgtable_l5_enabled); > > #endif > > > > +#define RISCV_MEMSTART_ALIGN (1UL << SECTION_SIZE_BITS) > > + > > phys_addr_t phys_ram_base __ro_after_init; > > EXPORT_SYMBOL(phys_ram_base); > > > > @@ -241,7 +243,8 @@ static void __init setup_bootmem(void) > > * at worst, we map the linear mapping with PMD mappings. > > */ > > if (!IS_ENABLED(CONFIG_XIP_KERNEL)) > > - phys_ram_base = memblock_start_of_DRAM() & PMD_MASK; > > + phys_ram_base = round_down(memblock_start_of_DRAM(), > > + RISCV_MEMSTART_ALIGN); > > No need to wrap this line. Also, is the RISCV_MEMSTART_ALIGN define > really needed? Maybe it is not so friendly to FLATMEM model if we always align phys_ram_base with SECTION_SIZE. I will refine the code and send again later. > > The kernel test robot had some build issues as well! > > > Björn
Hi Xu,
kernel test robot noticed the following build errors:
[auto build test ERROR on linus/master]
[also build test ERROR on v6.13-rc1 next-20241128]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Xu-Lu/riscv-mm-Fix-alignment-of-phys_ram_base/20241202-183801
base: linus/master
patch link: https://lore.kernel.org/r/20241202101601.48284-1-luxu.kernel%40bytedance.com
patch subject: [PATCH] riscv: mm: Fix alignment of phys_ram_base
config: riscv-allnoconfig (https://download.01.org/0day-ci/archive/20241202/202412022337.YEieoR2g-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20241202/202412022337.YEieoR2g-lkp@intel.com/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202412022337.YEieoR2g-lkp@intel.com/
All errors (new ones prefixed by >>):
In file included from include/linux/kernel.h:27,
from include/linux/cpumask.h:11,
from arch/riscv/include/asm/processor.h:55,
from arch/riscv/include/asm/thread_info.h:42,
from include/linux/thread_info.h:60,
from include/asm-generic/preempt.h:5,
from ./arch/riscv/include/generated/asm/preempt.h:1,
from include/linux/preempt.h:79,
from include/linux/spinlock.h:56,
from include/linux/mmzone.h:8,
from include/linux/gfp.h:7,
from include/linux/mm.h:7,
from arch/riscv/mm/init.c:10:
arch/riscv/mm/init.c: In function 'setup_bootmem':
>> arch/riscv/mm/init.c:62:41: error: 'SECTION_SIZE_BITS' undeclared (first use in this function)
62 | #define RISCV_MEMSTART_ALIGN (1UL << SECTION_SIZE_BITS)
| ^~~~~~~~~~~~~~~~~
include/linux/math.h:15:46: note: in definition of macro '__round_mask'
15 | #define __round_mask(x, y) ((__typeof__(x))((y)-1))
| ^
arch/riscv/mm/init.c:246:33: note: in expansion of macro 'round_down'
246 | phys_ram_base = round_down(memblock_start_of_DRAM(),
| ^~~~~~~~~~
arch/riscv/mm/init.c:247:44: note: in expansion of macro 'RISCV_MEMSTART_ALIGN'
247 | RISCV_MEMSTART_ALIGN);
| ^~~~~~~~~~~~~~~~~~~~
arch/riscv/mm/init.c:62:41: note: each undeclared identifier is reported only once for each function it appears in
62 | #define RISCV_MEMSTART_ALIGN (1UL << SECTION_SIZE_BITS)
| ^~~~~~~~~~~~~~~~~
include/linux/math.h:15:46: note: in definition of macro '__round_mask'
15 | #define __round_mask(x, y) ((__typeof__(x))((y)-1))
| ^
arch/riscv/mm/init.c:246:33: note: in expansion of macro 'round_down'
246 | phys_ram_base = round_down(memblock_start_of_DRAM(),
| ^~~~~~~~~~
arch/riscv/mm/init.c:247:44: note: in expansion of macro 'RISCV_MEMSTART_ALIGN'
247 | RISCV_MEMSTART_ALIGN);
| ^~~~~~~~~~~~~~~~~~~~
vim +/SECTION_SIZE_BITS +62 arch/riscv/mm/init.c
> 10 #include <linux/mm.h>
11 #include <linux/memblock.h>
12 #include <linux/initrd.h>
13 #include <linux/swap.h>
14 #include <linux/swiotlb.h>
15 #include <linux/sizes.h>
16 #include <linux/of_fdt.h>
17 #include <linux/of_reserved_mem.h>
18 #include <linux/libfdt.h>
19 #include <linux/set_memory.h>
20 #include <linux/dma-map-ops.h>
21 #include <linux/crash_dump.h>
22 #include <linux/hugetlb.h>
23 #ifdef CONFIG_RELOCATABLE
24 #include <linux/elf.h>
25 #endif
26 #include <linux/kfence.h>
27 #include <linux/execmem.h>
28
29 #include <asm/fixmap.h>
30 #include <asm/io.h>
31 #include <asm/kasan.h>
32 #include <asm/numa.h>
33 #include <asm/pgtable.h>
34 #include <asm/sections.h>
35 #include <asm/soc.h>
36 #include <asm/tlbflush.h>
37
38 #include "../kernel/head.h"
39
40 u64 new_vmalloc[NR_CPUS / sizeof(u64) + 1];
41
42 struct kernel_mapping kernel_map __ro_after_init;
43 EXPORT_SYMBOL(kernel_map);
44 #ifdef CONFIG_XIP_KERNEL
45 #define kernel_map (*(struct kernel_mapping *)XIP_FIXUP(&kernel_map))
46 #endif
47
48 #ifdef CONFIG_64BIT
49 u64 satp_mode __ro_after_init = !IS_ENABLED(CONFIG_XIP_KERNEL) ? SATP_MODE_57 : SATP_MODE_39;
50 #else
51 u64 satp_mode __ro_after_init = SATP_MODE_32;
52 #endif
53 EXPORT_SYMBOL(satp_mode);
54
55 #ifdef CONFIG_64BIT
56 bool pgtable_l4_enabled __ro_after_init = !IS_ENABLED(CONFIG_XIP_KERNEL);
57 bool pgtable_l5_enabled __ro_after_init = !IS_ENABLED(CONFIG_XIP_KERNEL);
58 EXPORT_SYMBOL(pgtable_l4_enabled);
59 EXPORT_SYMBOL(pgtable_l5_enabled);
60 #endif
61
> 62 #define RISCV_MEMSTART_ALIGN (1UL << SECTION_SIZE_BITS)
63
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
© 2016 - 2026 Red Hat, Inc.