On 01/01/20 at 10:36am, Dan Williams wrote: > On Tue, Dec 31, 2019 at 10:21 PM Dave Young <dyoung@xxxxxxxxxx> wrote: > > > > > > Does kexec preserve iomem? I.e. as long as the initial translation of > > > > efi entries to e820, and resulting resource tree, is preserved by > > > > successive kexec cycles then I think we're ok. > > > > > > It will not preserve them automatically, but that can be fixed if > > > needed. > > > > > > There are two places: > > > 1. the in kernel loader, we can do similar with below commit (for Soft > > > Reseved instead): > > > commit 980621daf368f2b9aa69c7ea01baa654edb7577b > > > Author: Lianbo Jiang <lijiang@xxxxxxxxxx> > > > Date: Tue Apr 23 09:30:07 2019 +0800 > > > > > > x86/crash: Add e820 reserved ranges to kdump kernel's e820 table > > > > Oops, that is for kdump only, for kexec, should update the kexec e820 > > table. But before doing that we need first to see if this is necessary. > > We can cross that bridge later, but I expect it will eventually be > necessary. The soft-reservation facility will become more prevalent as > more platforms ship with DRAM differentiated memory ranges, like > high-bandwidth-memory, and the system needs to reserve it from general > kernel allocations. See commit 262b45ae3ab4 "x86/efi: EFI soft > reservation to E820 enumeration" and commit fe3e5e65c06e "efi: > Enumerate EFI_MEMORY_SP" for more details. Ok, agreed the EFI_MEMORY_SP should be preserved across kexec reboot, I think those firmware provided EFI_MEMORY_SP should be persistent because the e820 table is just a copy. But I have no such hardware to test, could you do a test to confirm if possible? The test steps should be: # -s means to use kexec_file_load syscall kexec -s -l bzImage --initrd initramfs-file --reuse-cmdline reboot Maybe this should be fine for the time being. And leave the faked mem only works once during the physical boot? Thanks Dave _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
