Commit-ID: 8638100c52bb7782462b14aad102a4aaf0c7094c Gitweb: http://git.kernel.org/tip/8638100c52bb7782462b14aad102a4aaf0c7094c Author: Xunlei Pang <[email protected]> AuthorDate: Thu, 4 May 2017 09:42:51 +0800 Committer: Ingo Molnar <[email protected]> CommitDate: Mon, 8 May 2017 08:28:44 +0200
x86/kexec/64: Use gbpages for identity mappings if available Kexec sets up all identity mappings before booting into the new kernel, and this will cause extra memory consumption for paging structures which is quite considerable on modern machines with huge memory sizes. E.g. on a 32TB machine that is kdumping, it could waste around 128MB (around 4MB/TB) from the reserved memory after kexec sets all the identity mappings using the current 2MB page. Add to that the memory needed for the loaded kdump kernel, initramfs, etc., and it causes a kexec syscall -NOMEM failure. As a result, we had to enlarge reserved memory via "crashkernel=X" to work around this problem. This causes some trouble for distributions that use policies to evaluate the proper "crashkernel=X" value for users. So enable gbpages for kexec mappings. Signed-off-by: Xunlei Pang <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Brian Gerst <[email protected]> Cc: Dave Young <[email protected]> Cc: Denys Vlasenko <[email protected]> Cc: Eric Biederman <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Josh Poimboeuf <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Yinghai Lu <[email protected]> Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> --- arch/x86/kernel/machine_kexec_64.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c index 1d4f2b0..c25d277 100644 --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -122,6 +122,10 @@ static int init_pgtable(struct kimage *image, unsigned long start_pgtable) level4p = (pgd_t *)__va(start_pgtable); clear_page(level4p); + + if (direct_gbpages) + info.direct_gbpages = true; + for (i = 0; i < nr_pfn_mapped; i++) { mstart = pfn_mapped[i].start << PAGE_SHIFT; mend = pfn_mapped[i].end << PAGE_SHIFT;
