linux-kernel - Re: [PATCH v15 5/6] x86/boot: Parse SRAT address from RSDP and store immovable memory

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Date:   Thu, 17 Jan 2019 16:27:51 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Chao Fan <fanc.fnst@...fujitsu.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, keescook@...omium.org,
        bhe@...hat.com, msys.mizuma@...il.com, indou.takao@...fujitsu.com,
        caoj.fnst@...fujitsu.com
Subject: Re: [PATCH v15 5/6] x86/boot: Parse SRAT address from RSDP and store
 immovable memory

On Thu, Jan 17, 2019 at 11:20:27AM +0800, Chao Fan wrote:
> I have changed as you suggested, looks clear without type cast, and
> we need some variable as long to calculate the address, and at same
> time as the struct pointer to find it's length, so I change as below,
> and get_acpi_srat_table() return an unsigned long.
> How do you think of that.
> 
> int get_immovable_mem_num(void)

I'd call that

int count_immovable_mem_regions(void)

or

int enumerate_immovable_regions(void)

or so and put a comment above it explaining what it does and what it
returns.

"mem_num" is not clear what it is.

> {
>         unsigned long table_addr, table_end, table;
>         struct acpi_table_header *table_header;
>         struct acpi_subtable_header *sub_table;
>         char arg[MAX_ACPI_ARG_LENGTH];
>         int num = 0;
> 
>         if (cmdline_find_option("acpi", arg, sizeof(arg)) == 3 &&
>             !strncmp(arg, "off", 3))
>                 return;
> 
>         table_addr = get_acpi_srat_table();
>         if (!table_addr)
>                 return;
> 
>         table_header = (struct acpi_table_header *)table_addr;
>         table_end = table_addr + table_header->length;
>         table = table_addr + sizeof(struct acpi_table_srat);
> 
>         while (table + sizeof(struct acpi_subtable_header) < table_end) {
>                 sub_table = (struct acpi_subtable_header *)table;
>                 if (sub_table->type == ACPI_SRAT_TYPE_MEMORY_AFFINITY) {
>                         struct acpi_srat_mem_affinity *ma;
> 
>                         ma = (struct acpi_srat_mem_affinity *)table;
>                         if (!(ma->flags & ACPI_SRAT_MEM_HOT_PLUGGABLE)) {
>                                 immovable_mem[num].start = ma->base_address;
>                                 immovable_mem[num].size = ma->length;
>                                 num++;
>                         }
> 
>                         if (num >= MAX_NUMNODES*2) {
>                                 debug_putstr("Too many immovable memory regions, aborting.\n");
>                                 return 0;
>                         }
>                 }
>                 table += sub_table->length;
>         }
>         return num;
> }

That looks clean.

Thx.

-- 
Regards/Gruss,
    Boris.

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