On Mon, Sep 19, 2016 at 05:05:48PM +0100, James Morse wrote: > On 16/09/16 21:17, Ard Biesheuvel wrote: > > On 16 September 2016 at 17:04, James Morse <james.morse at arm.com> wrote: > >> Mark, Ard, how does/will reserved-memory work on an APCI only system? > > > > It works by accident, at the moment. We used to ignore both > > /memreserve/s and the /reserved-memory node, but due to some unrelated > > refactoring, we ended up honouring the reserved-memory node when > > booting via UEFI > > Okay, so kdump probably shouldn't rely on this behaviour... > > For an acpi-only system, we could get reserve_crashkernel() to copy the uefi > memory map into the reserved region, changing the region types for existing > kernel memory to EfiReservedMemoryType (for example) and fixing up the reserved > region boundaries. > > This second memory map could then be added alongside the real one in the > DT/chosen, and used in preference the second time we go through uefi_init() in > the crash kernel. Do we need add this map as the second one? Why not replace "linux,uefi-mmap-start" in a new blob? > kexec-tools would still need to keep the '/reserved-memory' node for non-uefi > systems. Yeah, but if we go in our own way on UEFI/ACPI systems, we may want to go in a DT-specific way, like PPC does, on DT systems. (That is, "linux,usable-memory" in memory nodes.) Thanks, -Takahiro AKASHI > Doing this doesn't depend on userspace, and means the uefi memory map is still > the one and only true source of memory layout information. If fixing it like > this is valid I don't think it should block kdump. > > ... I will think about this some more before trying to put it together. > > > > Thanks, > > James
