Re: [PATCH 01/21] e820, efi: add ACPI 6.0 persistent memory types

[Boaz Harrosh <boaz@plexistor.com>]

On 04/18/2015 04:35 AM, Dan Williams wrote:
> ACPI 6.0 formalizes e820-type-7 and efi-type-14 as persistent memory.
> Mark it "reserved" and allow it to be claimed by a persistent memory
> device driver.
> 
> This definition is in addition to the Linux kernel's existing type-12
> definition that was recently added in support of shipping platforms with
> NVDIMM support that predate ACPI 6.0 (which now classifies type-12 as
> OEM reserved).  We may choose to exploit this wealth of definitions for
> NVDIMMs to differentiate E820_PRAM (type-12) from E820_PMEM (type-7).
> One potential differentiation is that PMEM is not backed by struct page
> by default in contrast to PRAM.  For now, they are effectively treated
> as aliases by the mm.
> 
> Note, /proc/iomem can be consulted for differentiating legacy
> "Persistent RAM" E820_PRAM vs standard "Persistent I/O Memory"
> E820_PMEM.
> 
> Cc: Andy Lutomirski <luto@amacapital.net>
> Cc: Boaz Harrosh <boaz@plexistor.com>
> Cc: H. Peter Anvin <hpa@zytor.com>
> Cc: Jens Axboe <axboe@fb.com>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Christoph Hellwig <hch@lst.de>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> ---
>  arch/arm64/kernel/efi.c          |    1 +
>  arch/ia64/kernel/efi.c           |    1 +
>  arch/x86/boot/compressed/eboot.c |    4 ++++
>  arch/x86/include/uapi/asm/e820.h |    1 +
>  arch/x86/kernel/e820.c           |   25 +++++++++++++++++++------
>  arch/x86/platform/efi/efi.c      |    3 +++
>  include/linux/efi.h              |    3 ++-
>  7 files changed, 31 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/arm64/kernel/efi.c b/arch/arm64/kernel/efi.c
> index ab21e0d58278..9d4aa18f2a82 100644
> --- a/arch/arm64/kernel/efi.c
> +++ b/arch/arm64/kernel/efi.c
> @@ -158,6 +158,7 @@ static __init int is_reserve_region(efi_memory_desc_t *md)
>  	case EFI_BOOT_SERVICES_CODE:
>  	case EFI_BOOT_SERVICES_DATA:
>  	case EFI_CONVENTIONAL_MEMORY:
> +	case EFI_PERSISTENT_MEMORY:
>  		return 0;
>  	default:
>  		break;
> diff --git a/arch/ia64/kernel/efi.c b/arch/ia64/kernel/efi.c
> index c52d7540dc05..cd8b7485e396 100644
> --- a/arch/ia64/kernel/efi.c
> +++ b/arch/ia64/kernel/efi.c
> @@ -1227,6 +1227,7 @@ efi_initialize_iomem_resources(struct resource *code_resource,
>  			case EFI_RUNTIME_SERVICES_CODE:
>  			case EFI_RUNTIME_SERVICES_DATA:
>  			case EFI_ACPI_RECLAIM_MEMORY:
> +			case EFI_PERSISTENT_MEMORY:
>  			default:
>  				name = "reserved";
>  				break;
> diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
> index ef17683484e9..dde5bf7726f4 100644
> --- a/arch/x86/boot/compressed/eboot.c
> +++ b/arch/x86/boot/compressed/eboot.c
> @@ -1222,6 +1222,10 @@ static efi_status_t setup_e820(struct boot_params *params,
>  			e820_type = E820_NVS;
>  			break;
>  
> +		case EFI_PERSISTENT_MEMORY:
> +			e820_type = E820_PMEM;
> +			break;
> +
>  		default:
>  			continue;
>  		}
> diff --git a/arch/x86/include/uapi/asm/e820.h b/arch/x86/include/uapi/asm/e820.h
> index 960a8a9dc4ab..0f457e6eab18 100644
> --- a/arch/x86/include/uapi/asm/e820.h
> +++ b/arch/x86/include/uapi/asm/e820.h
> @@ -32,6 +32,7 @@
>  #define E820_ACPI	3
>  #define E820_NVS	4
>  #define E820_UNUSABLE	5
> +#define E820_PMEM	7
>  
>  /*
>   * This is a non-standardized way to represent ADR or NVDIMM regions that
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index 11cc7d54ec3f..410af501a941 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -137,6 +137,8 @@ static void __init e820_print_type(u32 type)
>  	case E820_RESERVED_KERN:
>  		printk(KERN_CONT "usable");
>  		break;
> +	case E820_PMEM:
> +	case E820_PRAM:

NACK!

This is the most important print in the system and it is a pure
user Interface. It has no effect what so ever on functionality
It is to Inform the user through dmesg what is the content of the
table.

>  	case E820_RESERVED:
>  		printk(KERN_CONT "reserved");
>  		break;
> @@ -149,9 +151,6 @@ static void __init e820_print_type(u32 type)
>  	case E820_UNUSABLE:
>  		printk(KERN_CONT "unusable");
>  		break;

+	case E820_PMEM:
> -	case E820_PRAM:
> -		printk(KERN_CONT "persistent (type %u)", type);
> -		break;

Just add the new (7) entry here please. Here Christoph has bike shed
it for you.

>  	default:
>  		printk(KERN_CONT "type %u", type);
>  		break;
> @@ -919,10 +918,26 @@ static inline const char *e820_type_to_string(int e820_type)
>  	case E820_NVS:	return "ACPI Non-volatile Storage";
>  	case E820_UNUSABLE:	return "Unusable memory";
>  	case E820_PRAM: return "Persistent RAM";
> +	case E820_PMEM: return "Persistent I/O Memory";
>  	default:	return "reserved";
>  	}
>  }
>  
> +static bool do_mark_busy(u32 type, struct resource *res)
> +{
> +	if (res->start < (1ULL<<20))
> +		return true;
> +
> +	switch (type) {
> +	case E820_RESERVED:
> +	case E820_PRAM:
> +	case E820_PMEM:
> +		return false;
> +	default:
> +		return true;
> +	}

Sigh. Again an unknown type comes out busy. Busy means
resource used. It does *not* mean "unknown type".

It just forces researchers to ignore the return value of
request_region. And not be protected by double lock. It
does not really prevent anything

Thanks
Boaz

> +}
> +
>  /*
>   * Mark e820 reserved areas as busy for the resource manager.
>   */
> @@ -952,9 +967,7 @@ void __init e820_reserve_resources(void)
>  		 * pci device BAR resource and insert them later in
>  		 * pcibios_resource_survey()
>  		 */
> -		if (((e820.map[i].type != E820_RESERVED) &&
> -		     (e820.map[i].type != E820_PRAM)) ||
> -		     res->start < (1ULL<<20)) {
> +		if (do_mark_busy(e820.map[i].type, res)) {
>  			res->flags |= IORESOURCE_BUSY;
>  			insert_resource(&iomem_resource, res);
>  		}
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index dbc8627a5cdf..a116e236ac3f 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -145,6 +145,9 @@ static void __init do_add_efi_memmap(void)
>  		case EFI_UNUSABLE_MEMORY:
>  			e820_type = E820_UNUSABLE;
>  			break;
> +		case EFI_PERSISTENT_MEMORY:
> +			e820_type = E820_PMEM;
> +			break;
>  		default:
>  			/*
>  			 * EFI_RESERVED_TYPE EFI_RUNTIME_SERVICES_CODE
> diff --git a/include/linux/efi.h b/include/linux/efi.h
> index cf7e431cbc73..28868504aa17 100644
> --- a/include/linux/efi.h
> +++ b/include/linux/efi.h
> @@ -85,7 +85,8 @@ typedef	struct {
>  #define EFI_MEMORY_MAPPED_IO		11
>  #define EFI_MEMORY_MAPPED_IO_PORT_SPACE	12
>  #define EFI_PAL_CODE			13
> -#define EFI_MAX_MEMORY_TYPE		14
> +#define EFI_PERSISTENT_MEMORY		14
> +#define EFI_MAX_MEMORY_TYPE		15
>  
>  /* Attribute values: */
>  #define EFI_MEMORY_UC		((u64)0x0000000000000001ULL)	/* uncached */
>