| Message ID | 1401266668-34365-1-git-send-email-wangnan0@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Catalin, Will Can we assume that HAVE_ARCH_PFN_VALID is alway yes on arm64? Looking at arm64/Kconfig, config ARCH_HAS_HOLES_MEMORYMODEL def_bool y if SPARSEMEM ... config HAVE_ARCH_PFN_VALID def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM is this intentional? -Takahiro AKASHI On 05/28/2014 05:44 PM, Wang Nan wrote: > This patch removes an irrational limitation for crash dump kernel on ARM > platform with SPARSEMEM enabled. > > Without this patch, crash reservation area for a crash dump kernel with > SPARSEMEM selected must occupy a full section plus 1MiB. If not, > elfcorehdr and some memory space used by the first kernel will unable to > get accessed. This is caused by pfn_valid: fast pfn_valid ragards any > pfn in a valid section as valid and prevents it to be ioremapped. > > This limitation wastes memory, because sections are always large and > crash dump kernel should be as small as possible. > > This patch selects HAVE_ARCH_PFN_VALID for CRASH_DUMP, makes crash dump > kernel to use strict version of pfn_valid(). > > Signed-off-by: Wang Nan <wangnan0@huawei.com> > --- > > This is the third time I post this patch. The previous records can be > retrived from: > > http://lists.infradead.org/pipermail/linux-arm-kernel/2014-May/256498.html > http://lists.infradead.org/pipermail/linux-arm-kernel/2014-May/257472.html > > Different from previous version, this patch select HAVE_ARCH_PFN_VALID > right after CRASH_DUMP config entry. > > --- > > arch/arm/Kconfig | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig > index c57ddcb..d5ffbb1 100644 > --- a/arch/arm/Kconfig > +++ b/arch/arm/Kconfig > @@ -2160,6 +2160,7 @@ config ATAGS_PROC > > config CRASH_DUMP > bool "Build kdump crash kernel (EXPERIMENTAL)" > + select HAVE_ARCH_PFN_VALID if SPARSEMEM > help > Generate crash dump after being started by kexec. This should > be normally only set in special crash dump kernels which are >
On Thu, May 29, 2014 at 05:54:02AM +0100, AKASHI Takahiro wrote: > Catalin, Will > > Can we assume that HAVE_ARCH_PFN_VALID is alway yes on arm64? > Looking at arm64/Kconfig, > config ARCH_HAS_HOLES_MEMORYMODEL > def_bool y if SPARSEMEM > ... > config HAVE_ARCH_PFN_VALID > def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM > > is this intentional? Looks like an artifact of the way we constructed those option, so yes, we could just make that a def_bool y if you like. Will
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index c57ddcb..d5ffbb1 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -2160,6 +2160,7 @@ config ATAGS_PROC config CRASH_DUMP bool "Build kdump crash kernel (EXPERIMENTAL)" + select HAVE_ARCH_PFN_VALID if SPARSEMEM help Generate crash dump after being started by kexec. This should be normally only set in special crash dump kernels which are
This patch removes an irrational limitation for crash dump kernel on ARM platform with SPARSEMEM enabled. Without this patch, crash reservation area for a crash dump kernel with SPARSEMEM selected must occupy a full section plus 1MiB. If not, elfcorehdr and some memory space used by the first kernel will unable to get accessed. This is caused by pfn_valid: fast pfn_valid ragards any pfn in a valid section as valid and prevents it to be ioremapped. This limitation wastes memory, because sections are always large and crash dump kernel should be as small as possible. This patch selects HAVE_ARCH_PFN_VALID for CRASH_DUMP, makes crash dump kernel to use strict version of pfn_valid(). Signed-off-by: Wang Nan <wangnan0@huawei.com> --- This is the third time I post this patch. The previous records can be retrived from: http://lists.infradead.org/pipermail/linux-arm-kernel/2014-May/256498.html http://lists.infradead.org/pipermail/linux-arm-kernel/2014-May/257472.html Different from previous version, this patch select HAVE_ARCH_PFN_VALID right after CRASH_DUMP config entry. --- arch/arm/Kconfig | 1 + 1 file changed, 1 insertion(+)