diff mbox series

[v2,3/3] riscv/kexec: load initrd high in available memory

Message ID 67c8eb9eea25717c2c8208d9bfbfaa39e6e2a1c6.1690365011.git.petr.tesarik.ext@huawei.com (mailing list archive)
State Accepted
Commit 0ccd2e803745ddcb2381760a1ddde09b4f39a34e
Headers show
Series RISC-V: Fix a few kexec_file_load(2) failures | expand

Checks

Context Check Description
conchuod/cover_letter success Series has a cover letter
conchuod/tree_selection success Guessed tree name to be fixes at HEAD ab2dbc7acced
conchuod/fixes_present success Fixes tag present in non-next series
conchuod/maintainers_pattern success MAINTAINERS pattern errors before the patch: 4 and now 4
conchuod/verify_signedoff success Signed-off-by tag matches author and committer
conchuod/kdoc success Errors and warnings before: 0 this patch: 0
conchuod/build_rv64_clang_allmodconfig success Errors and warnings before: 9 this patch: 9
conchuod/module_param success Was 0 now: 0
conchuod/build_rv64_gcc_allmodconfig success Errors and warnings before: 9 this patch: 9
conchuod/build_rv32_defconfig success Build OK
conchuod/dtb_warn_rv64 success Errors and warnings before: 3 this patch: 3
conchuod/header_inline success No static functions without inline keyword in header files
conchuod/checkpatch success total: 0 errors, 0 warnings, 0 checks, 8 lines checked
conchuod/build_rv64_nommu_k210_defconfig success Build OK
conchuod/verify_fixes success Fixes tag looks correct
conchuod/build_rv64_nommu_virt_defconfig success Build OK

Commit Message

Petr Tesarik July 26, 2023, 9:54 a.m. UTC 
From: Torsten Duwe <duwe@suse.de>

When initrd is loaded low, the secondary kernel fails like this:

 INITRD: 0xdc581000+0x00eef000 overlaps in-use memory region

This initrd load address corresponds to the _end symbol, but the
reservation is aligned on PMD_SIZE, as explained by a comment in
setup_bootmem().

It is technically possible to align the initrd load address accordingly,
leaving a hole between the end of kernel and the initrd, but it is much
simpler to allocate the initrd top-down.

Fixes: 838b3e28488f ("RISC-V: Load purgatory in kexec_file")
Signed-off-by: Torsten Duwe <duwe@suse.de>
Signed-off-by: Petr Tesarik <petr.tesarik.ext@huawei.com>
Cc: stable@vger.kernel.org
---
 arch/riscv/kernel/elf_kexec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Conor Dooley July 26, 2023, 4:38 p.m. UTC | #1 
On Wed, Jul 26, 2023 at 11:54:01AM +0200, Petr Tesarik wrote:
> From: Torsten Duwe <duwe@suse.de>
> 
> When initrd is loaded low, the secondary kernel fails like this:
> 
>  INITRD: 0xdc581000+0x00eef000 overlaps in-use memory region
> 
> This initrd load address corresponds to the _end symbol, but the
> reservation is aligned on PMD_SIZE, as explained by a comment in
> setup_bootmem().
> 
> It is technically possible to align the initrd load address accordingly,
> leaving a hole between the end of kernel and the initrd, but it is much
> simpler to allocate the initrd top-down.
> 
> Fixes: 838b3e28488f ("RISC-V: Load purgatory in kexec_file")
> Signed-off-by: Torsten Duwe <duwe@suse.de>
> Signed-off-by: Petr Tesarik <petr.tesarik.ext@huawei.com>
> Cc: stable@vger.kernel.org

Trying to align it might be worthwhile, but the simple fix makes sense
for now & w.r.t backporting.

Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

Thanks,
Conor.
Petr Tesarik July 26, 2023, 6:27 p.m. UTC | #2 
On 7/26/2023 6:38 PM, Conor Dooley wrote:
> On Wed, Jul 26, 2023 at 11:54:01AM +0200, Petr Tesarik wrote:
>> From: Torsten Duwe <duwe@suse.de>
>>
>> When initrd is loaded low, the secondary kernel fails like this:
>>
>>  INITRD: 0xdc581000+0x00eef000 overlaps in-use memory region
>>
>> This initrd load address corresponds to the _end symbol, but the
>> reservation is aligned on PMD_SIZE, as explained by a comment in
>> setup_bootmem().
>>
>> It is technically possible to align the initrd load address accordingly,
>> leaving a hole between the end of kernel and the initrd, but it is much
>> simpler to allocate the initrd top-down.
>>
>> Fixes: 838b3e28488f ("RISC-V: Load purgatory in kexec_file")
>> Signed-off-by: Torsten Duwe <duwe@suse.de>
>> Signed-off-by: Petr Tesarik <petr.tesarik.ext@huawei.com>
>> Cc: stable@vger.kernel.org
> 
> Trying to align it might be worthwhile, but the simple fix makes sense
> for now & w.r.t backporting.

On a second thought, allocating the initrd at the top of the range is
probably even better, because the kernel can unpack to low addresses,
resulting in less fragmented memory. See diagrams.

Top-down initrd:

+----------+          +----------+
|  initrd  |          |          |
+----------+          |   free   |
|          |          |          |
|          |  unpack  +----------+
|   free   |  ----->  | unpacked |
|          |          |  initrd  |
+----------+          +----------+
|  kernel  |          |  kernel  |
+----------+          +----------+


Aligned initrd:

+----------+          +----------+
|          |          |   free   |
|          |          +----------|
|   free   |          | unpacked |
|          |          |  initrd  |
+----------+  unpack  +----------+
|  initrd  |  ----->  |   free   |
+----------+          +----------+
|  kernel  |          |  kernel  |
+----------+          +----------+

Petr T
diff mbox series

Patch

diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
index 38390d3bdcac..c08bb5c3b385 100644
--- a/arch/riscv/kernel/elf_kexec.c
+++ b/arch/riscv/kernel/elf_kexec.c
@@ -281,7 +281,7 @@  static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
 		kbuf.buffer = initrd;
 		kbuf.bufsz = kbuf.memsz = initrd_len;
 		kbuf.buf_align = PAGE_SIZE;
-		kbuf.top_down = false;
+		kbuf.top_down = true;
 		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;
 		ret = kexec_add_buffer(&kbuf);
 		if (ret)