On Tue, Nov 21, 2017 at 07:59:01AM +0000, Liuwenliang (Abbott Liu) wrote: > On Nov 17, 2017 21:49 Marc Zyngier [mailto:marc.zyngier@xxxxxxx] wrote: > >On Sat, 18 Nov 2017 10:40:08 +0000 > >"Liuwenliang (Abbott Liu)" <liuwenliang@xxxxxxxxxx> wrote: > >> On Nov 17, 2017 15:36 Christoffer Dall [mailto:cdall@xxxxxxxxxx] wrote: > Please don't ask people to limit to 4GB of physical space on CPU > supporting LPAE, please don't ask people to guaranteed to have some > memory below 4GB on CPU supporting LPAE. I don't think that Marc is suggesting that you'd always use the 32-bit accessors on an LPAE system, just that all the definitions should exist regardless of configuration. So rather than this: > +#ifdef CONFIG_ARM_LPAE > +#define TTBR0 __ACCESS_CP15_64(0, c2) > +#define TTBR1 __ACCESS_CP15_64(1, c2) > +#define PAR __ACCESS_CP15_64(0, c7) > +#else > +#define TTBR0 __ACCESS_CP15(c2, 0, c0, 0) > +#define TTBR1 __ACCESS_CP15(c2, 0, c0, 1) > +#define PAR __ACCESS_CP15(c7, 0, c4, 0) > +#endif ... you'd have the following in cp15.h: #define TTBR0_64 __ACCESS_CP15_64(0, c2) #define TTBR1_64 __ACCESS_CP15_64(1, c2) #define PAR_64 __ACCESS_CP15_64(0, c7) #define TTBR0_32 __ACCESS_CP15(c2, 0, c0, 0) #define TTBR1_32 __ACCESS_CP15(c2, 0, c0, 1) #define PAR_32 __ACCESS_CP15(c7, 0, c4, 0) ... and elsewhere, where it matters, we choose which to use depending on the kernel configuration, e.g. void set_ttbr0(u64 val) { if (IS_ENABLED(CONFIG_ARM_LPAE)) write_sysreg(val, TTBR0_64); else write_sysreg(val, TTBR0_32); } Thanks, Mark. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
