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SubjectRe: [PATCH 01/11] kexec_file: allow archs to handle special regions while locating memory hole
Hi Hari,

is there any good reason to add two more functions with a very similar
name to an existing function? AFAICS all you need is a way to call a
PPC64-specific function from within kexec_add_buffer (PATCH 4/11), so
you could add something like this:

int __weak arch_kexec_locate_mem_hole(struct kexec_buf *kbuf)
{
return 0;
}

Call this function from kexec_add_buffer where appropriate and then
override it for PPC64 (it roughly corresponds to your
kexec_locate_mem_hole_ppc64() from PATCH 4/11).

FWIW it would make it easier for me to follow the resulting code.

Petr T

On Sat, 27 Jun 2020 00:34:43 +0530
Hari Bathini <hbathini@linux.ibm.com> wrote:

> Some archs can have special memory regions, within the given memory
> range, which can't be used for the buffer in a kexec segment. As
> kexec_add_buffer() function is being called from generic code as well,
> add weak arch_kexec_add_buffer definition for archs to override & take
> care of special regions before trying to locate a memory hole.
>
> Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
> ---
> include/linux/kexec.h | 5 +++++
> kernel/kexec_file.c | 37 +++++++++++++++++++++++++++++++++----
> 2 files changed, 38 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index 1776eb2..1237682 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -195,6 +195,11 @@ int __weak arch_kexec_apply_relocations(struct purgatory_info *pi,
> const Elf_Shdr *relsec,
> const Elf_Shdr *symtab);
>
> +extern int arch_kexec_add_buffer(struct kexec_buf *kbuf);
> +
> +/* arch_kexec_add_buffer calls this when it is ready */
> +extern int __kexec_add_buffer(struct kexec_buf *kbuf);
> +
> extern int kexec_add_buffer(struct kexec_buf *kbuf);
> int kexec_locate_mem_hole(struct kexec_buf *kbuf);
>
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index bb05fd5..a0b4f7f 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -669,10 +669,6 @@ int kexec_locate_mem_hole(struct kexec_buf *kbuf)
> */
> int kexec_add_buffer(struct kexec_buf *kbuf)
> {
> -
> - struct kexec_segment *ksegment;
> - int ret;
> -
> /* Currently adding segment this way is allowed only in file mode */
> if (!kbuf->image->file_mode)
> return -EINVAL;
> @@ -696,6 +692,25 @@ int kexec_add_buffer(struct kexec_buf *kbuf)
> kbuf->memsz = ALIGN(kbuf->memsz, PAGE_SIZE);
> kbuf->buf_align = max(kbuf->buf_align, PAGE_SIZE);
>
> + return arch_kexec_add_buffer(kbuf);
> +}
> +
> +/**
> + * __kexec_add_buffer - arch_kexec_add_buffer would call this function after
> + * updating kbuf, to place a buffer in a kexec segment.
> + * @kbuf: Buffer contents and memory parameters.
> + *
> + * This function assumes that kexec_mutex is held.
> + * On successful return, @kbuf->mem will have the physical address of
> + * the buffer in memory.
> + *
> + * Return: 0 on success, negative errno on error.
> + */
> +int __kexec_add_buffer(struct kexec_buf *kbuf)
> +{
> + struct kexec_segment *ksegment;
> + int ret;
> +
> /* Walk the RAM ranges and allocate a suitable range for the buffer */
> ret = kexec_locate_mem_hole(kbuf);
> if (ret)
> @@ -711,6 +726,20 @@ int kexec_add_buffer(struct kexec_buf *kbuf)
> return 0;
> }
>
> +/**
> + * arch_kexec_add_buffer - Some archs have memory regions within the given
> + * range that can't be used to place a kexec segment.
> + * Such archs can override this function to take care
> + * of them before trying to locate the memory hole.
> + * @kbuf: Buffer contents and memory parameters.
> + *
> + * Return: 0 on success, negative errno on error.
> + */
> +int __weak arch_kexec_add_buffer(struct kexec_buf *kbuf)
> +{
> + return __kexec_add_buffer(kbuf);
> +}
> +
> /* Calculate and store the digest of segments */
> static int kexec_calculate_store_digests(struct kimage *image)
> {
>

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