| Message ID | 20201103095857.078043987@linutronix.de (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | mm/highmem: Preemptible variant of kmap_atomic & friends | expand |
On Tue, Nov 3, 2020 at 10:27 AM Thomas Gleixner <tglx@linutronix.de> wrote: > > kmap_types.h is a misnomer because the old atomic MAP based array does not > exist anymore and the whole indirection of architectures including > kmap_types.h is inconinstent and does not allow to provide guard page > debugging for this misfeature. > > Add a common header file which defines the mapping stack size for all > architectures. Will be used when converting architectures over to a > generic kmap_local/atomic implementation. > > The array size is chosen with the following constraints in mind: > > - The deepest nest level in one context is 3 according to code > inspection. > > - The worst case nesting for the upcoming reemptible version would be: > > 2 maps in task context and a fault inside > 2 maps in the fault handler > 3 maps in softirq > 2 maps in interrupt > > So a total of 16 is sufficient and probably overestimated. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Arnd Bergmann <arnd@arndb.de>
--- a/include/asm-generic/Kbuild +++ b/include/asm-generic/Kbuild @@ -31,6 +31,7 @@ mandatory-y += irq_regs.h mandatory-y += irq_work.h mandatory-y += kdebug.h mandatory-y += kmap_types.h +mandatory-y += kmap_size.h mandatory-y += kprobes.h mandatory-y += linkage.h mandatory-y += local.h --- /dev/null +++ b/include/asm-generic/kmap_size.h @@ -0,0 +1,12 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_GENERIC_KMAP_SIZE_H +#define _ASM_GENERIC_KMAP_SIZE_H + +/* For debug this provides guard pages between the maps */ +#ifdef CONFIG_DEBUG_HIGHMEM +# define KM_MAX_IDX 33 +#else +# define KM_MAX_IDX 16 +#endif + +#endif
kmap_types.h is a misnomer because the old atomic MAP based array does not exist anymore and the whole indirection of architectures including kmap_types.h is inconinstent and does not allow to provide guard page debugging for this misfeature. Add a common header file which defines the mapping stack size for all architectures. Will be used when converting architectures over to a generic kmap_local/atomic implementation. The array size is chosen with the following constraints in mind: - The deepest nest level in one context is 3 according to code inspection. - The worst case nesting for the upcoming reemptible version would be: 2 maps in task context and a fault inside 2 maps in the fault handler 3 maps in softirq 2 maps in interrupt So a total of 16 is sufficient and probably overestimated. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> --- V3: New patch --- include/asm-generic/Kbuild | 1 + include/asm-generic/kmap_size.h | 12 ++++++++++++ 2 files changed, 13 insertions(+)