Commit-ID: 97b67ae559947f1e208439a1bf6a734da3087006 Gitweb: http://git.kernel.org/tip/97b67ae559947f1e208439a1bf6a734da3087006 Author: Jan Beulich <jbeul...@suse.com> AuthorDate: Tue, 4 Nov 2014 08:50:48 +0000 Committer: Thomas Gleixner <t...@linutronix.de> CommitDate: Tue, 4 Nov 2014 20:43:14 +0100
x86-64: Use RIP-relative addressing for most per-CPU accesses Observing that per-CPU data (in the SMP case) is reachable by exploiting 64-bit address wraparound (building on the default kernel load address being at 16Mb), the one byte shorter RIP-relative addressing form can be used for most per-CPU accesses. The one exception are the "stable" reads, where the use of the "P" operand modifier prevents the compiler from using RIP-relative addressing, but is unavoidable due to the use of the "p" constraint (side note: with gcc 4.9.x the intended effect of this isn't being achieved anymore, see gcc bug 63637). With the dependency on the minimum kernel load address, arbitrarily low values for CONFIG_PHYSICAL_START are now no longer possible. A link time assertion is being added, directing to the need to increase that value when it triggers. Signed-off-by: Jan Beulich <jbeul...@suse.com> Link: http://lkml.kernel.org/r/5458a1780200007800044...@mail.emea.novell.com Signed-off-by: Thomas Gleixner <t...@linutronix.de> --- arch/x86/include/asm/percpu.h | 59 ++++++++++++++++++++++++++++++++----------- arch/x86/kernel/vmlinux.lds.S | 2 ++ 2 files changed, 46 insertions(+), 15 deletions(-) diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h index 74da317..e0ba66c 100644 --- a/arch/x86/include/asm/percpu.h +++ b/arch/x86/include/asm/percpu.h @@ -64,7 +64,7 @@ #define __percpu_prefix "" #endif -#define __percpu_arg(x) __percpu_prefix "%P" #x +#define __percpu_arg(x) __percpu_prefix "%" #x /* * Initialized pointers to per-cpu variables needed for the boot @@ -179,29 +179,58 @@ do { \ } \ } while (0) -#define percpu_from_op(op, var, constraint) \ +#define percpu_from_op(op, var) \ ({ \ typeof(var) pfo_ret__; \ switch (sizeof(var)) { \ case 1: \ asm(op "b "__percpu_arg(1)",%0" \ : "=q" (pfo_ret__) \ - : constraint); \ + : "m" (var)); \ break; \ case 2: \ asm(op "w "__percpu_arg(1)",%0" \ : "=r" (pfo_ret__) \ - : constraint); \ + : "m" (var)); \ break; \ case 4: \ asm(op "l "__percpu_arg(1)",%0" \ : "=r" (pfo_ret__) \ - : constraint); \ + : "m" (var)); \ break; \ case 8: \ asm(op "q "__percpu_arg(1)",%0" \ : "=r" (pfo_ret__) \ - : constraint); \ + : "m" (var)); \ + break; \ + default: __bad_percpu_size(); \ + } \ + pfo_ret__; \ +}) + +#define percpu_stable_op(op, var) \ +({ \ + typeof(var) pfo_ret__; \ + switch (sizeof(var)) { \ + case 1: \ + asm(op "b "__percpu_arg(P1)",%0" \ + : "=q" (pfo_ret__) \ + : "p" (&(var))); \ + break; \ + case 2: \ + asm(op "w "__percpu_arg(P1)",%0" \ + : "=r" (pfo_ret__) \ + : "p" (&(var))); \ + break; \ + case 4: \ + asm(op "l "__percpu_arg(P1)",%0" \ + : "=r" (pfo_ret__) \ + : "p" (&(var))); \ + break; \ + case 8: \ + asm(op "q "__percpu_arg(P1)",%0" \ + : "=r" (pfo_ret__) \ + : "p" (&(var))); \ break; \ default: __bad_percpu_size(); \ } \ @@ -359,11 +388,11 @@ do { \ * per-thread variables implemented as per-cpu variables and thus * stable for the duration of the respective task. */ -#define this_cpu_read_stable(var) percpu_from_op("mov", var, "p" (&(var))) +#define this_cpu_read_stable(var) percpu_stable_op("mov", var) -#define raw_cpu_read_1(pcp) percpu_from_op("mov", (pcp), "m"(pcp)) -#define raw_cpu_read_2(pcp) percpu_from_op("mov", (pcp), "m"(pcp)) -#define raw_cpu_read_4(pcp) percpu_from_op("mov", (pcp), "m"(pcp)) +#define raw_cpu_read_1(pcp) percpu_from_op("mov", pcp) +#define raw_cpu_read_2(pcp) percpu_from_op("mov", pcp) +#define raw_cpu_read_4(pcp) percpu_from_op("mov", pcp) #define raw_cpu_write_1(pcp, val) percpu_to_op("mov", (pcp), val) #define raw_cpu_write_2(pcp, val) percpu_to_op("mov", (pcp), val) @@ -381,9 +410,9 @@ do { \ #define raw_cpu_xchg_2(pcp, val) percpu_xchg_op(pcp, val) #define raw_cpu_xchg_4(pcp, val) percpu_xchg_op(pcp, val) -#define this_cpu_read_1(pcp) percpu_from_op("mov", (pcp), "m"(pcp)) -#define this_cpu_read_2(pcp) percpu_from_op("mov", (pcp), "m"(pcp)) -#define this_cpu_read_4(pcp) percpu_from_op("mov", (pcp), "m"(pcp)) +#define this_cpu_read_1(pcp) percpu_from_op("mov", pcp) +#define this_cpu_read_2(pcp) percpu_from_op("mov", pcp) +#define this_cpu_read_4(pcp) percpu_from_op("mov", pcp) #define this_cpu_write_1(pcp, val) percpu_to_op("mov", (pcp), val) #define this_cpu_write_2(pcp, val) percpu_to_op("mov", (pcp), val) #define this_cpu_write_4(pcp, val) percpu_to_op("mov", (pcp), val) @@ -435,7 +464,7 @@ do { \ * 32 bit must fall back to generic operations. */ #ifdef CONFIG_X86_64 -#define raw_cpu_read_8(pcp) percpu_from_op("mov", (pcp), "m"(pcp)) +#define raw_cpu_read_8(pcp) percpu_from_op("mov", pcp) #define raw_cpu_write_8(pcp, val) percpu_to_op("mov", (pcp), val) #define raw_cpu_add_8(pcp, val) percpu_add_op((pcp), val) #define raw_cpu_and_8(pcp, val) percpu_to_op("and", (pcp), val) @@ -444,7 +473,7 @@ do { \ #define raw_cpu_xchg_8(pcp, nval) percpu_xchg_op(pcp, nval) #define raw_cpu_cmpxchg_8(pcp, oval, nval) percpu_cmpxchg_op(pcp, oval, nval) -#define this_cpu_read_8(pcp) percpu_from_op("mov", (pcp), "m"(pcp)) +#define this_cpu_read_8(pcp) percpu_from_op("mov", pcp) #define this_cpu_write_8(pcp, val) percpu_to_op("mov", (pcp), val) #define this_cpu_add_8(pcp, val) percpu_add_op((pcp), val) #define this_cpu_and_8(pcp, val) percpu_to_op("and", (pcp), val) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 49edf2d..00bf300 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -186,6 +186,8 @@ SECTIONS * start another segment - init. */ PERCPU_VADDR(INTERNODE_CACHE_BYTES, 0, :percpu) + ASSERT(SIZEOF(.data..percpu) < CONFIG_PHYSICAL_START, + "per-CPU data too large - increase CONFIG_PHYSICAL_START") #endif INIT_TEXT_SECTION(PAGE_SIZE) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
