linux-kernel - Re: [PATCH] powerpc/kexec_file: Restore FDT size estimation for kdump kernel

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Message-ID: <5a28907e-9231-7a19-62ff-3ed1c0282642@linux.microsoft.com>
Date:   Fri, 19 Feb 2021 08:00:03 -0800
From:   Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
To:     Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org
Cc:     kexec@...ts.infradead.org, Hari Bathini <hbathini@...ux.ibm.com>,
        Rob Herring <robh@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] powerpc/kexec_file: Restore FDT size estimation for kdump
 kernel

On 2/19/21 6:25 AM, Thiago Jung Bauermann wrote:

One small nit in the function header (please see below), but otherwise 
the change looks good.

Reviewed-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>

> Commit 2377c92e37fe ("powerpc/kexec_file: fix FDT size estimation for kdump
> kernel") fixed how elf64_load() estimates the FDT size needed by the
> crashdump kernel.
> 
> At the same time, commit 130b2d59cec0 ("powerpc: Use common
> of_kexec_alloc_and_setup_fdt()") changed the same code to use the generic
> function of_kexec_alloc_and_setup_fdt() to calculate the FDT size. That
> change made the code overestimate it a bit by counting twice the space
> required for the kernel command line and /chosen properties.
> 
> Therefore change kexec_fdt_totalsize_ppc64() to calculate just the extra
> space needed by the kdump kernel, and change the function name so that it
> better reflects what the function is now doing.
> 
> Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
> ---
>   arch/powerpc/include/asm/kexec.h  |  2 +-
>   arch/powerpc/kexec/elf_64.c       |  2 +-
>   arch/powerpc/kexec/file_load_64.c | 26 ++++++++------------------
>   3 files changed, 10 insertions(+), 20 deletions(-)
> 
> Applies on top of next-20210219.
> 
> diff --git a/arch/powerpc/include/asm/kexec.h b/arch/powerpc/include/asm/kexec.h
> index baab158e215c..5a11cc8d2350 100644
> --- a/arch/powerpc/include/asm/kexec.h
> +++ b/arch/powerpc/include/asm/kexec.h
> @@ -128,7 +128,7 @@ int load_crashdump_segments_ppc64(struct kimage *image,
>   int setup_purgatory_ppc64(struct kimage *image, const void *slave_code,
>   			  const void *fdt, unsigned long kernel_load_addr,
>   			  unsigned long fdt_load_addr);
> -unsigned int kexec_fdt_totalsize_ppc64(struct kimage *image);
> +unsigned int kexec_extra_fdt_size_ppc64(struct kimage *image);
>   int setup_new_fdt_ppc64(const struct kimage *image, void *fdt,
>   			unsigned long initrd_load_addr,
>   			unsigned long initrd_len, const char *cmdline);
> diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
> index 0492ca6003f3..5a569bb51349 100644
> --- a/arch/powerpc/kexec/elf_64.c
> +++ b/arch/powerpc/kexec/elf_64.c
> @@ -104,7 +104,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>   
>   	fdt = of_kexec_alloc_and_setup_fdt(image, initrd_load_addr,
>   					   initrd_len, cmdline,
> -					   kexec_fdt_totalsize_ppc64(image));
> +					   kexec_extra_fdt_size_ppc64(image));
>   	if (!fdt) {
>   		pr_err("Error setting up the new device tree.\n");
>   		ret = -EINVAL;
> diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
> index 3609de30a170..8541ba731908 100644
> --- a/arch/powerpc/kexec/file_load_64.c
> +++ b/arch/powerpc/kexec/file_load_64.c
> @@ -927,37 +927,27 @@ int setup_purgatory_ppc64(struct kimage *image, const void *slave_code,
>   }
>   
>   /**
> - * kexec_fdt_totalsize_ppc64 - Return the estimated size needed to setup FDT
> - *                             for kexec/kdump kernel.
> - * @image:                     kexec image being loaded.
> + * kexec_extra_fdt_size_ppc63 - Return the estimated size needed to setup FDT

Perhaps change to

"Return the estimated additional size needed to setup FDT for 
kexec/kdump kernel"?

  -lakshmi

> + *                              for kexec/kdump kernel.
> + * @image:                      kexec image being loaded.
>    *
> - * Returns the estimated size needed for kexec/kdump kernel FDT.
> + * Returns the estimated extra size needed for kexec/kdump kernel FDT.
>    */
> -unsigned int kexec_fdt_totalsize_ppc64(struct kimage *image)
> +unsigned int kexec_extra_fdt_size_ppc64(struct kimage *image)
>   {
> -	unsigned int fdt_size;
>   	u64 usm_entries;
>   
> -	/*
> -	 * The below estimate more than accounts for a typical kexec case where
> -	 * the additional space is to accommodate things like kexec cmdline,
> -	 * chosen node with properties for initrd start & end addresses and
> -	 * a property to indicate kexec boot..
> -	 */
> -	fdt_size = fdt_totalsize(initial_boot_params) + (2 * COMMAND_LINE_SIZE);
>   	if (image->type != KEXEC_TYPE_CRASH)
> -		return fdt_size;
> +		return 0;
>   
>   	/*
> -	 * For kdump kernel, also account for linux,usable-memory and
> +	 * For kdump kernel, account for linux,usable-memory and
>   	 * linux,drconf-usable-memory properties. Get an approximate on the
>   	 * number of usable memory entries and use for FDT size estimation.
>   	 */
>   	usm_entries = ((memblock_end_of_DRAM() / drmem_lmb_size()) +
>   		       (2 * (resource_size(&crashk_res) / drmem_lmb_size())));
> -	fdt_size += (unsigned int)(usm_entries * sizeof(u64));
> -
> -	return fdt_size;
> +	return (unsigned int)(usm_entries * sizeof(u64));
>   }
>   
>   /**
>