Re: [PATCH 2/3] x86: add a is_e820_ram() helper

From: Boaz Harrosh
Date: Thu Mar 26 2015 - 11:49:52 EST

On 03/26/2015 11:34 AM, Christoph Hellwig wrote:
<>

Please re-post this patch stand alone because git am on this will
Give me the wrong title and commit message

small comments ...

> From: Christoph Hellwig <hch@xxxxxx>
> Date: Wed, 25 Mar 2015 12:24:11 +0100
> Subject: x86: add support for the non-standard protected e820 type
>
> Various recent BIOSes support NVDIMMs or ADR using a non-standard
> e820 memory type, and Intel supplied reference Linux code using this
> type to various vendors.
>
> Wire this e820 table type up to export platform devices for the pmem
> driver so that we can use it in Linux, and also provide a memmap=
> argument to manually tag memory as protected, which can be used
> if the BIOSs doesn't use the standard nonstandard interface, or
> we just want to test the pmem driver with regular memory.
>
> Based on an earlier patch from Dave Jiang <dave.jiang@xxxxxxxxx>
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Tested-by: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
> ---
> Documentation/kernel-parameters.txt | 6 ++++
> arch/x86/Kconfig | 10 ++++++
> arch/x86/include/asm/setup.h | 6 ++++
> arch/x86/include/uapi/asm/e820.h | 10 ++++++
> arch/x86/kernel/Makefile | 1 +
> arch/x86/kernel/e820.c | 31 ++++++++++++----
> arch/x86/kernel/pmem.c | 70 +++++++++++++++++++++++++++++++++++++
> arch/x86/kernel/setup.c | 2 ++
> 8 files changed, 130 insertions(+), 6 deletions(-)
> create mode 100644 arch/x86/kernel/pmem.c
>
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index bfcb1a6..c87122d 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -1965,6 +1965,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
> or
> memmap=0x10000$0x18690000
>
> + memmap=nn[KMG]!ss[KMG]
> + [KNL,X86] Mark specific memory as protected.
> + Region of memory to be used, from ss to ss+nn.
> + The memory region may be marked as e820 type 12 (0xc)
> + and is NVDIMM or ADR memory.
> +

Do we need to escape "\!" this character on grub command line ? It might
help to note that. I did like the original "|" BTW

> memory_corruption_check=0/1 [X86]
> Some BIOSes seem to corrupt the first 64k of
> memory when doing things like suspend/resume.
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index b7d31ca..c0e8ee3 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1430,6 +1430,16 @@ config ILLEGAL_POINTER_VALUE
>
> source "mm/Kconfig"
>
> +config X86_PMEM_LEGACY
> + bool "Support non-standard NVDIMMs and ADR protected memory"
> + help
> + Treat memory marked using the non-standard e820 type of 12 as used
> + by the Intel Sandy Bridge-EP reference BIOS as protected memory.
> + The kernel will offer these regions to the pmem driver so
> + they can be used for persistent storage.
> +
> + Say Y if unsure.
> +
> config HIGHPTE
> bool "Allocate 3rd-level pagetables from highmem"
> depends on HIGHMEM
> diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
> index ff4e7b2..2352fde 100644
> --- a/arch/x86/include/asm/setup.h
> +++ b/arch/x86/include/asm/setup.h
> @@ -57,6 +57,12 @@ extern void x86_ce4100_early_setup(void);
> static inline void x86_ce4100_early_setup(void) { }
> #endif
>
> +#ifdef CONFIG_X86_PMEM_LEGACY
> +void reserve_pmem(void);
> +#else
> +static inline void reserve_pmem(void) { }
> +#endif
> +
> #ifndef _SETUP
>
> #include <asm/espfix.h>
> diff --git a/arch/x86/include/uapi/asm/e820.h b/arch/x86/include/uapi/asm/e820.h
> index d993e33..ce0d0bf 100644
> --- a/arch/x86/include/uapi/asm/e820.h
> +++ b/arch/x86/include/uapi/asm/e820.h
> @@ -33,6 +33,16 @@
> #define E820_NVS 4
> #define E820_UNUSABLE 5
>
> +/*
> + * This is a non-standardized way to represent ADR or NVDIMM regions that
> + * persist over a reboot. The kernel will ignore their special capabilities
> + * unless the CONFIG_X86_PMEM_LEGACY option is set.
> + *
> + * Note that older platforms also used 6 for the same type of memory,
> + * but newer versions switched to 12 as 6 was assigned differently. Some
> + * time they will learn..
> + */
> +#define E820_PRAM 12

Why the PRAM Name. For one 2/3 of this patch say PMEM the Kconfig
to enable is _PMEM_, the driver stack that gets loaded is pmem,
so PRAM is unexpected.

Also I do believe PRAM is not the correct name. Yes NvDIMMs are RAM,
but there are other not RAM technologies that can be supported exactly
the same way.
MEM is a more general name meaning "on the memory bus". I think.

I would love the consistency.

>
> /*
> * reserved RAM used by kernel itself
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index cdb1b70..971f18c 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -94,6 +94,7 @@ obj-$(CONFIG_KVM_GUEST) += kvm.o kvmclock.o
> obj-$(CONFIG_PARAVIRT) += paravirt.o paravirt_patch_$(BITS).o
> obj-$(CONFIG_PARAVIRT_SPINLOCKS)+= paravirt-spinlocks.o
> obj-$(CONFIG_PARAVIRT_CLOCK) += pvclock.o
> +obj-$(CONFIG_X86_PMEM_LEGACY) += pmem.o
>
> obj-$(CONFIG_PCSPKR_PLATFORM) += pcspeaker.o
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index 46201de..4bd525a 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -149,6 +149,9 @@ static void __init e820_print_type(u32 type)
> case E820_UNUSABLE:
> printk(KERN_CONT "unusable");
> break;
> + case E820_PRAM:
> + printk(KERN_CONT "persistent (type %u)", type);

This case can only mean 12 in this patch. (I think historically
you had a Kconfig to set its Number

> + break;
> default:
> printk(KERN_CONT "type %u", type);
> break;
> @@ -688,8 +691,15 @@ void __init e820_mark_nosave_regions(unsigned long limit_pfn)
> register_nosave_region(pfn, PFN_UP(ei->addr));
>
> pfn = PFN_DOWN(ei->addr + ei->size);
> - if (ei->type != E820_RAM && ei->type != E820_RESERVED_KERN)
> +
> + switch (ei->type) {
> + case E820_RAM:
> + case E820_PRAM:
> + case E820_RESERVED_KERN:
> + break;
> + default:
> register_nosave_region(PFN_UP(ei->addr), pfn);
> + }
>
> if (pfn >= limit_pfn)
> break;
> @@ -748,7 +758,7 @@ u64 __init early_reserve_e820(u64 size, u64 align)
> /*
> * Find the highest page frame number we have available
> */
> -static unsigned long __init e820_end_pfn(unsigned long limit_pfn, unsigned type)
> +static unsigned long __init e820_end_pfn(unsigned long limit_pfn)
> {
> int i;
> unsigned long last_pfn = 0;
> @@ -759,7 +769,11 @@ static unsigned long __init e820_end_pfn(unsigned long limit_pfn, unsigned type)
> unsigned long start_pfn;
> unsigned long end_pfn;
>
> - if (ei->type != type)
> + /*
> + * Persistent memory is accounted as ram for purposes of
> + * establishing max_pfn and mem_map.
> + */
> + if (ei->type != E820_RAM && ei->type != E820_PRAM)
> continue;
>
> start_pfn = ei->addr >> PAGE_SHIFT;
> @@ -784,12 +798,12 @@ static unsigned long __init e820_end_pfn(unsigned long limit_pfn, unsigned type)
> }
> unsigned long __init e820_end_of_ram_pfn(void)
> {
> - return e820_end_pfn(MAX_ARCH_PFN, E820_RAM);
> + return e820_end_pfn(MAX_ARCH_PFN);
> }
>
> unsigned long __init e820_end_of_low_ram_pfn(void)
> {
> - return e820_end_pfn(1UL<<(32 - PAGE_SHIFT), E820_RAM);
> + return e820_end_pfn(1UL<<(32 - PAGE_SHIFT));
> }
>
> static void early_panic(char *msg)
> @@ -866,6 +880,9 @@ static int __init parse_memmap_one(char *p)
> } else if (*p == '$') {
> start_at = memparse(p+1, &p);
> e820_add_region(start_at, mem_size, E820_RESERVED);
> + } else if (*p == '!') {
> + start_at = memparse(p+1, &p);
> + e820_add_region(start_at, mem_size, E820_PRAM);
> } else
> e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1);
>
> @@ -907,6 +924,7 @@ static inline const char *e820_type_to_string(int e820_type)
> case E820_ACPI: return "ACPI Tables";
> case E820_NVS: return "ACPI Non-volatile Storage";
> case E820_UNUSABLE: return "Unusable memory";
> + case E820_PRAM: return "Persistent RAM";

if you change E820_PRAM, then Also here

> default: return "reserved";
> }
> }
> @@ -941,7 +959,8 @@ void __init e820_reserve_resources(void)
> * pcibios_resource_survey()
> */
> if (e820.map[i].type != E820_RESERVED || res->start < (1ULL<<20)) {
> - res->flags |= IORESOURCE_BUSY;
> + if (e820.map[i].type != E820_PRAM)
> + res->flags |= IORESOURCE_BUSY;
> insert_resource(&iomem_resource, res);
> }
> res++;
> diff --git a/arch/x86/kernel/pmem.c b/arch/x86/kernel/pmem.c
> new file mode 100644
> index 0000000..f970048
> --- /dev/null
> +++ b/arch/x86/kernel/pmem.c
> @@ -0,0 +1,70 @@
> +/*
> + * Copyright (c) 2009, Intel Corporation.
> + * Copyright (c) 2015, Christoph Hellwig.
> + */
> +#include <linux/memblock.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <asm/e820.h>
> +#include <asm/page_types.h>
> +#include <asm/setup.h>
> +
> +void __init reserve_pmem(void)
> +{
> + int i;
> +
> + for (i = 0; i < e820.nr_map; i++) {
> + struct e820entry *ei = &e820.map[i];
> +
> + if (ei->type != E820_PRAM)
> + continue;
> +
> + memblock_reserve(ei->addr, ei->addr + ei->size);
> + max_pfn_mapped = init_memory_mapping(
> + ei->addr < 1UL << 32 ? 1UL << 32 : ei->addr,
> + ei->addr + ei->size);
> + }
> +}
> +
> +static __init void register_pmem_device(struct resource *res)
> +{
> + struct platform_device *pdev;
> + int error;
> +
> + pdev = platform_device_alloc("pmem", PLATFORM_DEVID_AUTO);
> + if (!pdev)
> + return;
> +
> + error = platform_device_add_resources(pdev, res, 1);
> + if (error)
> + goto out_put_pdev;
> +
> + error = platform_device_add(pdev);
> + if (error)
> + goto out_put_pdev;
> + return;
> +out_put_pdev:
> + dev_warn(&pdev->dev, "failed to add pmem device!\n");
> + platform_device_put(pdev);
> +}
> +
> +static __init int register_pmem_devices(void)
> +{
> + int i;
> +
> + for (i = 0; i < e820.nr_map; i++) {
> + struct e820entry *ei = &e820.map[i];
> +
> + if (ei->type == E820_PRAM) {

See here it would be cleaner to ask for E820_PMEM in a
register_pmem_devices member

Just my $0.017

Thanks
Boaz

> + struct resource res = {
> + .flags = IORESOURCE_MEM,
> + .start = ei->addr,
> + .end = ei->addr + ei->size - 1,
> + };
> + register_pmem_device(&res);
> + }
> + }
> +
> + return 0;
> +}
> +device_initcall(register_pmem_devices);
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index 0a2421c..f2bed2b 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1158,6 +1158,8 @@ void __init setup_arch(char **cmdline_p)
>
> early_acpi_boot_init();
>
> + reserve_pmem();
> +
> initmem_init();
> dma_contiguous_reserve(max_pfn_mapped << PAGE_SHIFT);
>
>

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