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    Subject[PATCH] Do not round per_cpu_ptr_to_phys to page boundary
    Date
    The phys_addr_t per_cpu_ptr_to_phys() function ignores the offset within a 
    page, whenever not using a simple translation using __pa().

    Without this patch /sys/devices/system/cpu/cpu*/crash_notes shows incorrect
    values, which breaks kdump. Other things may also be broken.

    Signed-off-by: Petr Tesarik <ptesarik@suse.cz>

    diff --git a/mm/percpu.c b/mm/percpu.c
    index 3bb810a..1a1b5ac 100644
    --- a/mm/percpu.c
    +++ b/mm/percpu.c
    @@ -998,6 +998,7 @@ phys_addr_t per_cpu_ptr_to_phys(void *addr)
    bool in_first_chunk = false;
    unsigned long first_low, first_high;
    unsigned int cpu;
    + phys_addr_t page_addr;

    /*
    * The following test on unit_low/high isn't strictly
    @@ -1023,9 +1024,10 @@ phys_addr_t per_cpu_ptr_to_phys(void *addr)
    if (!is_vmalloc_addr(addr))
    return __pa(addr);
    else
    - return page_to_phys(vmalloc_to_page(addr));
    + page_addr = page_to_phys(vmalloc_to_page(addr));
    } else
    - return page_to_phys(pcpu_addr_to_page(addr));
    + page_addr = page_to_phys(pcpu_addr_to_page(addr));
    + return page_addr + offset_in_page(addr);
    }

    /**

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