On Mon, Sep 08, 2014 at 03:21:05PM +0100, Mark Salter wrote: > On Mon, 2014-09-08 at 15:06 +0100, Mark Rutland wrote: > > Hi Mark, > > > > On Mon, Sep 08, 2014 at 02:31:42PM +0100, Mark Salter wrote: > > > Commit 86c8b27a01cf: > > > "arm64: ignore DT memreserve entries when booting in UEFI mode > > > > > > prevents early_init_fdt_scan_reserved_mem() from being called for > > > arm64 kernels booting via UEFI. This was done because the kernel > > > will use the UEFI memory map to determine reserved memory regions. > > > That approach has problems in that early_init_fdt_scan_reserved_mem() > > > also reserves the FDT itself and any node-specific reserved memory. > > > By chance of some kernel configs, the FDT may be overwritten before > > > it can be unflattened and the kernel will fail to boot. More subtle > > > problems will result if the FDT has node specific reserved memory > > > which is not really reserved. > > > > That doesn't sound like fun; apologies for allowing such brokenness > > through in the first place. > > Heh. It was obvious that DT unflattening was broken, but bisecting > didn't help much because I kept finding patches which when reverted > made the problem go away even though they obviously weren't the > cause. Yeah, those types of bugs are never fun. I recall a similar situation with the __INIT annotation in the versatile pen code. > > [...] > > > > > + /* > > > + * Delete all memory reserve map entries. When booting via UEFI, > > > + * kernel will use the UEFI memory map to find reserved regions. > > > + */ > > > + num_rsv = fdt_num_mem_rsv(fdt); > > > + for (i = 0; i < num_rsv; i++) > > > + fdt_del_mem_rsv(fdt, i); > > > > I don't think that's right. Won't the memreserve entries shift down by > > one each time we call fdt_del_mem_rsv? > > > > Shouldn't this be something like: > > > > while (fdt_num_mem_rsv(fdt)) > > fdt_del_mem_rsv(fdt, 0); > > > > Or we could count downwards. > > > > Sigh. Yes, you are right. I only tested with one reserved region. > I think counting down would be the way to go. I'll send a fixed > patch shortly. Ok, that sounds fine by me; make sure you add my ack :) Thanks, Mark. -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
