Messages in this thread Patch in this message | | | Subject | per_cpu_ptr_to_phys() failure on UV x86_64 | From | Cliff Wickman <> | Date | Thu, 17 Jun 2010 11:20:26 -0500 |
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kdump is failing on an SGI UV system because it depends on /sys/devices/system/cpu/cpuN/crash_notes. And these files contain bad addresses for cpus beyond cpu 0.
This occurs using 2.6.35-rc3 code. But the same problem looks present in 2.6.33.
The problem traces to per_cpu_ptr_to_phys() -> pcpu_addr_to_page() -> vmalloc_to_page() for per-cpu addresses not in the first per-cpu 'chunk', but not in the VMALLOC_START/VMALLOC_END range.
I wonder why this shows up on UV but not other x86_64's? I've included a patch that solves this for me. But I defer to the authors for a proper solution.
This is where per_cpu_ptr_to_phys() is called for this /sys file: static ssize_t show_crash_notes(struct sys_device *dev, struct ... ... addr = per_cpu_ptr_to_phys(per_cpu_ptr(crash_notes, cpunum)); rc = sprintf(buf, "%Lx\n", addr); return rc; }
The problem, without the below patch: (but a couple of printk's)
uv3-sys:/tmp/cpw # cat /sys/devices/system/cpu/cpu0/crash_notes 1c1b040 uv3-sys:/tmp/cpw # cat /sys/devices/system/cpu/cpu1/crash_notes db74000000000000 uv3-sys:/tmp/cpw # cat /sys/devices/system/cpu/cpu2/crash_notes db74000000000000 uv3-sys:/tmp/cpw # dmesg | tail -n 6 [ 133.883009] cpw: per_cpu_ptr_to_phys addr ffff880001c1b040 [ 133.883012] cpw: per_cpu_ptr_to_phys returning 0x1c1b040 [ 136.910178] cpw: per_cpu_ptr_to_phys addr ffff880001c3b040 [ 136.910181] cpw: per_cpu_ptr_to_phys returning 0xdb74000000000000 [ 140.304825] cpw: per_cpu_ptr_to_phys addr ffff880001c5b040 [ 140.304828] cpw: per_cpu_ptr_to_phys returning 0xdb74000000000000
With the below patch: (plus a couple of printk's)
uv3-sys: # cat /sys/devices/system/cpu/cpu0/crash_notes 1c1b040 uv3-sys: # cat /sys/devices/system/cpu/cpu1/crash_notes 1c3b040 uv3-sys: # cat /sys/devices/system/cpu/cpu2/crash_notes 1c5b040 uv3-sys: # dmesg | tail -n 6 [ 130.411358] cpw: per_cpu_ptr_to_phys addr ffff880001c1b040 [ 130.411361] cpw: per_cpu_ptr_to_phys returning 0x1c1b040 [ 135.420702] cpw: per_cpu_ptr_to_phys addr ffff880001c3b040 [ 135.420705] cpw: per_cpu_ptr_to_phys returning 0x1c3b040 [ 139.514014] cpw: per_cpu_ptr_to_phys addr ffff880001c5b040 [ 139.514016] cpw: per_cpu_ptr_to_phys returning 0x1c5b040
Diffed against 2.6.35-rc5
Signed-off-by: Cliff Wickman <cpw@sgi.com> --- mm/percpu.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
Index: linux-2.6.35-rc3/mm/percpu.c =================================================================== --- linux-2.6.35-rc3.orig/mm/percpu.c +++ linux-2.6.35-rc3/mm/percpu.c @@ -978,12 +978,11 @@ bool is_kernel_percpu_address(unsigned l */ phys_addr_t per_cpu_ptr_to_phys(void *addr) { + if ((unsigned long)addr < VMALLOC_START || + (unsigned long)addr >= VMALLOC_END) + return __pa(addr); if (pcpu_addr_in_first_chunk(addr)) { - if ((unsigned long)addr < VMALLOC_START || - (unsigned long)addr >= VMALLOC_END) - return __pa(addr); - else - return page_to_phys(vmalloc_to_page(addr)); + return page_to_phys(vmalloc_to_page(addr)); } else return page_to_phys(pcpu_addr_to_page(addr)); }
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