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Date:   Thu, 22 Nov 2018 15:42:02 +0800
From:   Dave Young <dyoung@redhat.com>
To:     Lianbo Jiang <lijiang@redhat.com>
Cc:     linux-kernel@vger.kernel.org, bhe@redhat.com, x86@kernel.org,
        kexec@lists.infradead.org, mingo@redhat.com, bp@alien8.de,
        tglx@linutronix.de, akpm@linux-foundation.org
Subject: Re: [PATCH 1/2 v7] resource: add the new I/O resource descriptor
 'IORES_DESC_RESERVED'
Message-ID: <20181122074202.GA8524@dhcp-128-65.nay.redhat.com>
References: <20181115095529.21220-1-lijiang@redhat.com>
 <20181115095529.21220-2-lijiang@redhat.com>
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On 11/15/18 at 05:55pm, Lianbo Jiang wrote:
> The upstream kernel can not accurately add the e820 reserved type to
> kdump krenel e820 table.
> 
> Kdump uses walk_iomem_res_desc() to iterate io resources, then adds
> the matched resource ranges to the e820 table for kdump kernel. But,
> when convert the e820 type into the iores descriptor, several e820
> types are converted to 'IORES_DESC_NONE' in this function e820_type
> _to_iores_desc(). So the walk_iomem_res_desc() will get unnecessary
> types(such as E820_TYPE_RAM/E820_TYPE_UNUSABLE/E820_TYPE_KERN) when
> walk through io resources by the descriptor 'IORES_DESC_NONE'.
> 
> This patch adds the new I/O resource descriptor 'IORES_DESC_RESERVED'
> for the iomem resources search interfaces. It is helpful to exactly
> match the reserved resource ranges when walking through iomem resources.
> 
> Suggested-by: Dave Young <dyoung@redhat.com>
> Signed-off-by: Lianbo Jiang <lijiang@redhat.com>
> ---
> Changes since v5:
> 1. Improve the patch log
> 
> Changes since v6:
> 1. Modify this patch, and add the new I/O resource descriptor
>    'IORES_DESC_RESERVED' for the iomem resources search interfaces.
> 2. Improve patch log.
> 
>  arch/x86/kernel/e820.c | 2 +-
>  include/linux/ioport.h | 1 +
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index 50895c2f937d..57fafdafb860 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -1048,10 +1048,10 @@ static unsigned long __init e820_type_to_iores_desc(struct e820_entry *entry)
>  	case E820_TYPE_NVS:		return IORES_DESC_ACPI_NV_STORAGE;
>  	case E820_TYPE_PMEM:		return IORES_DESC_PERSISTENT_MEMORY;
>  	case E820_TYPE_PRAM:		return IORES_DESC_PERSISTENT_MEMORY_LEGACY;
> +	case E820_TYPE_RESERVED:	return IORES_DESC_RESERVED;
>  	case E820_TYPE_RESERVED_KERN:	/* Fall-through: */
>  	case E820_TYPE_RAM:		/* Fall-through: */
>  	case E820_TYPE_UNUSABLE:	/* Fall-through: */
> -	case E820_TYPE_RESERVED:	/* Fall-through: */
>  	default:			return IORES_DESC_NONE;
>  	}
>  }
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index da0ebaec25f0..6ed59de48bd5 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -133,6 +133,7 @@ enum {
>  	IORES_DESC_PERSISTENT_MEMORY_LEGACY	= 5,
>  	IORES_DESC_DEVICE_PRIVATE_MEMORY	= 6,
>  	IORES_DESC_DEVICE_PUBLIC_MEMORY		= 7,
> +	IORES_DESC_RESERVED			= 8,
>  };

There more works for a new iores desc. Originally IORES_DESC_NONE
is assumed to include reserved e820 type so all code path relates to
IORES_DESC_NONE should be carefully checked and ensure they still work after
your changes.

>  
>  /* helpers to define resources */
> -- 
> 2.17.1
> 
> 
> _______________________________________________
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> kexec@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/kexec

Thanks
Dave