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Subject: Re: [PATCH 01/11] kexec_file: allow archs to handle special regions
 while locating memory hole
To:     Hari Bathini <hbathini@linux.ibm.com>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Andrew Morton <akpm@linux-foundation.org>
Cc:     Pingfan Liu <piliu@redhat.com>,
        Kexec-ml <kexec@lists.infradead.org>,
        Petr Tesarik <ptesarik@suse.cz>,
        Mahesh J Salgaonkar <mahesh@linux.ibm.com>,
        Sourabh Jain <sourabhjain@linux.ibm.com>,
        lkml <linux-kernel@vger.kernel.org>,
        linuxppc-dev <linuxppc-dev@ozlabs.org>,
        Mimi Zohar <zohar@linux.ibm.com>,
        Vivek Goyal <vgoyal@redhat.com>,
        Dave Young <dyoung@redhat.com>,
        Thiago Jung Bauermann <bauerman@linux.ibm.com>,
        Eric Biederman <ebiederm@xmission.com>
References: <159319825403.16351.7253978047621755765.stgit@hbathini.in.ibm.com>
 <159319828304.16351.6990340111766605842.stgit@hbathini.in.ibm.com>
From:   Christophe Leroy <christophe.leroy@csgroup.eu>
Message-ID: <9a976370-caef-1beb-d172-bcb0b17e9b78@csgroup.eu>
Date:   Sat, 27 Jun 2020 08:30:22 +0200
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Le 26/06/2020 à 21:04, Hari Bathini a écrit :
> 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);
> +

extern keywork is useless here, please remove (checkpatch also complains 
about it usually).

> +/* arch_kexec_add_buffer calls this when it is ready */
> +extern int __kexec_add_buffer(struct kexec_buf *kbuf);
> +

same

>   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)
>   {
> 

Christophe