diff options
Diffstat (limited to 'arch/parisc/include/asm/shmparam.h')
| -rw-r--r-- | arch/parisc/include/asm/shmparam.h | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/arch/parisc/include/asm/shmparam.h b/arch/parisc/include/asm/shmparam.h index 628ddc22faa8..5a95b0f62b87 100644 --- a/arch/parisc/include/asm/shmparam.h +++ b/arch/parisc/include/asm/shmparam.h @@ -1,8 +1,23 @@ +/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _ASMPARISC_SHMPARAM_H #define _ASMPARISC_SHMPARAM_H -#define __ARCH_FORCE_SHMLBA 1 - -#define SHMLBA 0x00400000 /* attach addr needs to be 4 Mb aligned */ +/* + * PA-RISC uses virtually indexed & physically tagged (VIPT) caches + * which has strict requirements when two pages to the same physical + * address are accessed through different mappings. Read the section + * "Address Aliasing" in the arch docs for more detail: + * PA-RISC 1.1 (page 3-6): + * https://parisc.wiki.kernel.org/images-parisc/6/68/Pa11_acd.pdf + * PA-RISC 2.0 (page F-5): + * https://parisc.wiki.kernel.org/images-parisc/7/73/Parisc2.0.pdf + * + * For Linux we allow kernel and userspace to map pages on page size + * granularity (SHMLBA) but have to ensure that, if two pages are + * mapped to the same physical address, the virtual and physical + * addresses modulo SHM_COLOUR are identical. + */ +#define SHMLBA PAGE_SIZE /* attach addr a multiple of this */ +#define SHM_COLOUR 0x00400000 /* shared mappings colouring */ #endif /* _ASMPARISC_SHMPARAM_H */ |