linux-kernel - Re: [RFC v3 2/3] fadump: Reserve page-aligned boot_memory_size during fadump_reserve

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Message-ID: <96241074-7b78-4b7a-a539-ef8a1055c198@linux.ibm.com>
Date: Tue, 15 Oct 2024 17:04:10 +0530
From: Madhavan Srinivasan <maddy@...ux.ibm.com>
To: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>,
        linuxppc-dev@...ts.ozlabs.org
Cc: linux-mm@...ck.org, Sourabh Jain <sourabhjain@...ux.ibm.com>,
        Hari Bathini <hbathini@...ux.ibm.com>, Zi Yan <ziy@...dia.com>,
        David Hildenbrand <david@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        "Aneesh Kumar K . V" <aneesh.kumar@...nel.org>,
        Donet Tom <donettom@...ux.vnet.ibm.com>,
        LKML
 <linux-kernel@...r.kernel.org>,
        Sachin P Bappalige <sachinpb@...ux.ibm.com>
Subject: Re: [RFC v3 2/3] fadump: Reserve page-aligned boot_memory_size during
 fadump_reserve_mem



On 10/11/24 8:30 PM, Ritesh Harjani (IBM) wrote:
> This patch refactors all CMA related initialization and alignment code
> to within fadump_cma_init() which gets called in the end. This also means
> that we keep [reserve_dump_area_start, boot_memory_size] page aligned
> during fadump_reserve_mem(). Then later in fadump_cma_init() we extract the
> aligned chunk and provide it to CMA. This inherently also fixes an issue in
> the current code where the reserve_dump_area_start is not aligned
> when the physical memory can have holes and the suitable chunk starts at
> an unaligned boundary.
> 
> After this we should be able to call fadump_cma_init() independently
> later in setup_arch() where pageblock_order is non-zero.
> 
> Suggested-by: Sourabh Jain <sourabhjain@...ux.ibm.com>
> Acked-by: Hari Bathini <hbathini@...ux.ibm.com>
> Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
> ---
>  arch/powerpc/kernel/fadump.c | 34 ++++++++++++++++++++++------------
>  1 file changed, 22 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> index 162327d66982..ffaec625b7a8 100644
> --- a/arch/powerpc/kernel/fadump.c
> +++ b/arch/powerpc/kernel/fadump.c
> @@ -80,7 +80,7 @@ static struct cma *fadump_cma;
>   */
>  static void __init fadump_cma_init(void)
>  {
> -	unsigned long long base, size;
> +	unsigned long long base, size, end;
>  	int rc;
>  
>  	if (!fw_dump.fadump_supported || !fw_dump.fadump_enabled ||
> @@ -92,8 +92,24 @@ static void __init fadump_cma_init(void)
>  	if (fw_dump.nocma || !fw_dump.boot_memory_size)
>  		return;
>  
> +	/*
> +	 * [base, end) should be reserved during early init in
> +	 * fadump_reserve_mem(). No need to check this here as
> +	 * cma_init_reserved_mem() already checks for overlap.
> +	 * Here we give the aligned chunk of this reserved memory to CMA.
> +	 */
>  	base = fw_dump.reserve_dump_area_start;
>  	size = fw_dump.boot_memory_size;
> +	end = base + size;
> +
> +	base = ALIGN(base, CMA_MIN_ALIGNMENT_BYTES);
> +	end = ALIGN_DOWN(end, CMA_MIN_ALIGNMENT_BYTES);
> +	size = end - base;
> +
> +	if (end <= base) {
> +		pr_warn("%s: Too less memory to give to CMA\n", __func__);
> +		return;
> +	}
>  

just minor, other prints are all "cma", any reason for "CMA" here?


>  	rc = cma_init_reserved_mem(base, size, 0, "fadump_cma", &fadump_cma);
>  	if (rc) {
> @@ -116,11 +132,12 @@ static void __init fadump_cma_init(void)
>  	/*
>  	 * So we now have successfully initialized cma area for fadump.
>  	 */
> -	pr_info("Initialized 0x%lx bytes cma area at %ldMB from 0x%lx "
> +	pr_info("Initialized [0x%llx, %luMB] cma area from [0x%lx, %luMB] "
>  		"bytes of memory reserved for firmware-assisted dump\n",
> -		cma_get_size(fadump_cma),
> -		(unsigned long)cma_get_base(fadump_cma) >> 20,
> -		fw_dump.reserve_dump_area_size);
> +		cma_get_base(fadump_cma), cma_get_size(fadump_cma) >> 20,
> +		fw_dump.reserve_dump_area_start,
> +		fw_dump.boot_memory_size >> 20);
> +	return;
>  }
>  #else
>  static void __init fadump_cma_init(void) { }
> @@ -553,13 +570,6 @@ int __init fadump_reserve_mem(void)
>  	if (!fw_dump.dump_active) {
>  		fw_dump.boot_memory_size =
>  			PAGE_ALIGN(fadump_calculate_reserve_size());
> -#ifdef CONFIG_CMA
> -		if (!fw_dump.nocma) {
> -			fw_dump.boot_memory_size =
> -				ALIGN(fw_dump.boot_memory_size,
> -				      CMA_MIN_ALIGNMENT_BYTES);
> -		}
> -#endif
>  
>  		bootmem_min = fw_dump.ops->fadump_get_bootmem_min();
>  		if (fw_dump.boot_memory_size < bootmem_min) {