On 09/05/18 at 10:02am, Thomas Gleixner wrote: > On Tue, 4 Sep 2018, H. Peter Anvin wrote: > > > On 09/04/18 01:42, Kirill A. Shutemov wrote: > > > > > > Switching between 4- and 5-level paging modes (in either direction) > > > requires paing disabling. It means the code that does the switching has to > > > be under 4G otherwise we would lose control. > > > > > > We handle the switching correctly in kernel decompression code, but not on > > > kexec caller side. > > > > > > XLF_5LEVEL indicates that kernel decompression code can deal with > > > switching between paging modes and it's safe to jump there in 5-level > > > paging mode. > > > > > > As an alternative we can change kexec to switch to 4-level paging mode > > > before starting the new kernel. Not sure how hard it will be. > > > > > > > Have a flag saying entering in 5-level mode is fine. However, you really > > should support returning to 4-level mode in kexec. It is *much* easier to do > > on the caller side as you have total control of memory allocation there. > > Works for a regular kexec, but not for starting a crash kernel.... Agree, it's not appropriate to do this after normal kernel crashed and prepare to jump to 2nd kernel. Can this patchset be merged? I will post patches to kexec-tools utility since it will make use of these flags. Thanks Baoquan _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
