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Date: Sun, 19 Apr 2015 10:46:38 +0300
From: Boaz Harrosh <boaz@...xistor.com>
To: Dan Williams <dan.j.williams@...el.com>, linux-nvdimm@...ts.01.org
CC: linux-kernel@...r.kernel.org,
Andy Lutomirski <luto@...capital.net>,
Jens Axboe <axboe@...com>, "H. Peter Anvin" <hpa@...or.com>,
Ross Zwisler <ross.zwisler@...ux.intel.com>,
Christoph Hellwig <hch@....de>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 01/21] e820, efi: add ACPI 6.0 persistent memory types
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@...capital.net>
> Cc: Boaz Harrosh <boaz@...xistor.com>
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: Jens Axboe <axboe@...com>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Christoph Hellwig <hch@....de>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> Reviewed-by: Ross Zwisler <ross.zwisler@...ux.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 */
>
--
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