Hi Julien, On 26/06/2023 14:56, Julien Grall wrote: > > > Hi, > > On 26/06/2023 12:56, Michal Orzel wrote: >> >> >> On 25/06/2023 22:49, Julien Grall wrote: >>> >>> >>> From: Julien Grall <[email protected]> >>> >>> UBSAN has been enabled a few years ago on x86 but was never >>> enabled on Arm because the final binary is bigger than 2MB ( >>> the maximum we can currently handled). >>> >>> With the recent rework, it is now possible to grow Xen over 2MB. >>> So there is no more roadblock to enable Xen other than increasing >>> the reserved area. >>> >>> On my setup, for arm32, the final binaray was very close to 4MB. >>> Furthermore, one may want to enable USBAN and GCOV which would put >>> the binary well-over 4MB (both features require for some space). >>> Therefore, increase the size to 8MB which should us some margin. >>> >>> Signed-off-by: Julien Grall <[email protected]> >>> >>> ---- >>> >>> The drawback with this approach is that we are adding 6 new >>> page-table (3 for boot and 3 for runtime) that are statically >>> allocated. So the final Xen binary will be 24KB bigger when >>> neither UBSAN nor GCOV. >>> >>> If this is not considered acceptable, then we could make the >>> size of configurable in the Kconfig and decide it based on the >>> features enabled. >> Both of these features are enabled only in a debug build of Xen, so >> another option would be to increase Xen size only for a debug build. > > At least UBSAN can be selected without DEBUG. For that you need to add > EXPERT. > > Anyway, from your comment, it is not clear to me whether you dislike the > existing approach (and why) or you are OK with the increase. Sorry, I was traveling and did not have time to complete review. I cannot see why increasing the size would be problematic so it is ok. That said, it could be a good idea to write some comment above XEN_VIRT_SIZE, that this value is somewhat exaggerated, so that we are on the safe side at the time of activating features like UBSAN/GCOV.
Also, it would be nice to update comments in head.S of both arm32 and arm64 above GLOBAL(start) that were left stating: "All of text+data+bss must fit in 2MB, or the initial pagetable code below will need adjustment." Other than that: Reviewed-by: Michal Orzel <[email protected]> ~Michal
