On Fri, Apr 9, 2021 at 3:59 PM Mike Rapoport <rppt@xxxxxxxxxxxxx> wrote: > > On Fri, Apr 09, 2021 at 02:46:17PM +0200, David Hildenbrand wrote: > > > > > Also, will that memory properly be exposed in the resource tree as > > > > > System RAM (e.g., /proc/iomem) ? Otherwise some things (/proc/kcore) > > > > > won't work as expected - the kernel won't be included in a dump. > > > Do we really need a XIP kernel to included in kdump? > > > And does not it sound weird to expose flash as System RAM in /proc/iomem? ;-) > > > > See my other mail, maybe we actually want something different. > > > > > > > > > I have just checked and it does not appear in /proc/iomem. > > > > > > > > Ok your conclusion would be to have struct page, I'm going to implement this > > > > version then using memblock as you described. > > > > > > I'm not sure this is required. With XIP kernel text never gets into RAM, so > > > it does not seem to require struct page. > > > > > > XIP by definition has some limitations relatively to "normal" operation, > > > so lack of kdump could be one of them. > > > > I agree. > > > > > > > > I might be wrong, but IMHO, artificially creating a memory map for part of > > > flash would cause more problems in the long run. > > > > Can you elaborate? > > Nothing particular, just a gut feeling. Usually, when you force something > it comes out the wrong way later. It's possible still that MTD_XIP is implemented allowing to write to the flash used for XIP. While flash is being written, memory map doesn't make sense at all. I can't come up with a real life example when it can actually lead to problems but it is indeed weird when System RAM suddenly becomes unreadable. I really don't think exposing it in /proc/iomem is a good idea. > > > BTW, how does XIP account the kernel text on other architectures that > > > implement it? > > > > Interesting point, I thought XIP would be something new on RISC-V (well, at > > least to me :) ). If that concept exists already, we better mimic what > > existing implementations do. > > I had quick glance at ARM, it seems that kernel text does not have memory > map and does not show up in System RAM. Exactly, and I believe ARM64 won't do that too when it gets its own XIP support (which is underway). Best regards, Vitaly
