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    SubjectRe: [PATCH 3/3] Limit E820 map when a user-defined memory map is specified
    On Fri, Jun 20, 2008 at 8:57 AM, Bernhard Walle <bwalle@suse.de> wrote:
    > This patch brings back limiting of the E820 map when a user-defined
    > E820 map is specified. While the behaviour of i386 (32 bit) was to limit
    > the E820 map (and /proc/iomem), the behaviour of x86-64 (64 bit) was not to
    > limit.

    then if you kexec new kernel, the second kernel will be have that
    limitation too.

    any problem that you encountered without this patch?

    YH

    >
    > That patch limits the E820 map again for both x86 architectures.
    >
    > Code was tested for compilation and booting on a 32 bit and 64 bit system.
    >
    >
    > Signed-off-by: Bernhard Walle <bwalle@suse.de>
    > ---
    > arch/x86/kernel/e820.c | 30 ++++++++++++++++++++++++++++++
    > 1 files changed, 30 insertions(+), 0 deletions(-)
    >
    > diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
    > index f5b1736..2e7d385 100644
    > --- a/arch/x86/kernel/e820.c
    > +++ b/arch/x86/kernel/e820.c
    > @@ -934,6 +934,33 @@ static void early_panic(char *msg)
    > panic(msg);
    > }
    >
    > +void __init e820_limit_regions(unsigned long long size)
    > +{
    > + unsigned long long current_addr;
    > + int i;
    > +
    > + for (i = 0; i < e820.nr_map; i++) {
    > + current_addr = e820.map[i].addr + e820.map[i].size;
    > + if (current_addr < size)
    > + continue;
    > +
    > + if (e820.map[i].type != E820_RAM)
    > + continue;
    > +
    > + if (e820.map[i].addr >= size) {
    > + /*
    > + * This region starts past the end of the
    > + * requested size, skip it completely.
    > + */
    > + e820.nr_map = i;
    > + } else {
    > + e820.nr_map = i + 1;
    > + e820.map[i].size -= current_addr - size;
    > + }
    > + return;
    > + }
    > +}
    > +
    > /* "mem=nopentium" disables the 4MB page tables. */
    > static int __init parse_memopt(char *p)
    > {
    > @@ -951,6 +978,8 @@ static int __init parse_memopt(char *p)
    >
    > mem_size = memparse(p, &p);
    > end_user_pfn = mem_size>>PAGE_SHIFT;
    > + e820_limit_regions(mem_size);
    > +
    > return 0;
    > }
    > early_param("mem", parse_memopt);
    > @@ -995,6 +1024,7 @@ static int __init parse_memmap_opt(char *p)
    > e820_add_region(start_at, mem_size, E820_RESERVED);
    > } else {
    > end_user_pfn = (mem_size >> PAGE_SHIFT);
    > + e820_limit_regions(mem_size);
    > }
    > return *p == '\0' ? 0 : -EINVAL;
    > }
    > --
    > 1.5.4.5
    >
    > --
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