Add kexec at lists.infradead.org to cc list. On 2014/5/15 15:14, Wang Nan wrote: > This patch makes crash dump kernel use arch pfn_valid defined in > arch/arm/mm/init.c instead of the one in include/linux/mmzone.h. > The goal of this patch is to remove some limitation when kexec loading > crash kernel while SPARSEMEM is enabled. > > Before this patch, if second kernel selects both CRASH_DUMP and > SPARSEMEM, the second kernel will recongnize memorys at the same section > with itself as valid memory, and prevents ioremap (see arm ioremap code, > arm doesn't allow valid memory to be ioremapped again). Which introduces > some limitations on positioning the crash kernel. For example: > > For a platform with SECTION_SIZE_BITS == 28 (256MiB) and > crashkernel=128M at 0x28000000 in kernel cmdline, the second > kernel is loaded at 0x28000000. Kexec puts elfcorehdr at > 0x2ff00000, and passes 'elfcorehdr=0x2ff00000 mem=130048K' to > second kernel. When second kernel start, it tries to use > ioremap to retrive its elfcorehrd. In this case, elfcodehdr is at the > same section of the second kernel, pfn_valid will recongnize > the page as valid, so ioremap will refuse to map it. > > Even if we put crash kernel at the boundary of two sections (such as > 129MB at 0x0x28000000 in the above situation), 0x20000000-0x28000000 used > by old kernel is still unable to retrived by crash kernel because they > are at the same section. > > This patch makes crash dump kernel use strict (and slow) version of > pfn_valid(), which makes crash kernel recongnize memory correctly. > > Signed-off-by: Wang Nan <wangnan0 at huawei.com> > Cc: Geng Hui <hui.geng at huawei.com> > Cc: Mika Westerberg <ext-mika.1.westerberg at nokia.com> > Cc: Simon Horman <horms at verge.net.au> > --- > arch/arm/Kconfig | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index db3c541..795b1d4 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -1800,7 +1800,7 @@ config ARCH_SELECT_MEMORY_MODEL > def_bool ARCH_SPARSEMEM_ENABLE > > config HAVE_ARCH_PFN_VALID > - def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM > + def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM || CRASH_DUMP > > config HIGHMEM > bool "High Memory Support" >
