On Mon, Sep 12, 2022 at 2:40 AM Arnd Bergmann <arnd@xxxxxxxx> wrote: > > > > On Sun, Sep 11, 2022, at 1:35 AM, Guo Ren wrote: > > On Sun, Sep 11, 2022 at 12:07 AM Arnd Bergmann <arnd@xxxxxxxx> wrote: > >> > >> On Sat, Sep 10, 2022, at 2:52 PM, Guo Ren wrote: > >> > On Thu, Sep 8, 2022 at 3:37 PM Arnd Bergmann <arnd@xxxxxxxx> wrote: > >> >> On Thu, Sep 8, 2022, at 4:25 AM, guoren@xxxxxxxxxx wrote: > >> >> > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx> > >> >> - When VMAP_STACK is set, make it possible to select non-power-of-two > >> >> stack sizes. Most importantly, 12KB should be a really interesting > >> >> choice as 8KB is probably still not enough for many 64-bit workloads, > >> >> but 16KB is often more than what you need. You probably don't > >> >> want to allow 64BIT/8KB without VMAP_STACK anyway since that just > >> >> makes it really hard to debug, so hiding the option when VMAP_STACK > >> >> is disabled may also be a good idea. > >> > I don't want this config to depend on VMAP_STACK. Some D1 chips would > >> > run with an 8K stack size and !VMAP_STACK. > >> > >> That sounds like a really bad idea, why would you want to risk > >> using such a small stack without CONFIG_VMAP_STACK? > >> > >> Are you worried about increased memory usage or something else? > > The requirement is from [1], and I think disabling CONFIG_VMAP_STACK > > would be the last step after serious testing. > > I still don't see why you need to turn off VMAP_STACK at all > if it works. The only downside I can see with using VMAP_STACK > on a 64-bit system is that it may expose bugs with device > drivers that do DMA to stack data. Once you have tested the > system successfully, you can also assume that you have no such > drivers. 1st, VMAP_STACK could be enabled&disabled in arch/Kconfig. If we don't force users to enable VMAP_STACK, why couldn't user adjust THREAD_SIZE? 2nd, VMAP_STACK is not free, we still need 1KB shadow_stack. The EXPERT is enough for your concern. > > Arnd -- Best Regards Guo Ren
