diff options
Diffstat (limited to 'arch/x86_64/kernel/vsyscall.c')
| -rw-r--r-- | arch/x86_64/kernel/vsyscall.c | 84 |
1 files changed, 82 insertions, 2 deletions
diff --git a/arch/x86_64/kernel/vsyscall.c b/arch/x86_64/kernel/vsyscall.c index f603037df162..902783bc4d53 100644 --- a/arch/x86_64/kernel/vsyscall.c +++ b/arch/x86_64/kernel/vsyscall.c @@ -26,6 +26,7 @@ #include <linux/seqlock.h> #include <linux/jiffies.h> #include <linux/sysctl.h> +#include <linux/getcpu.h> #include <asm/vsyscall.h> #include <asm/pgtable.h> @@ -33,11 +34,15 @@ #include <asm/fixmap.h> #include <asm/errno.h> #include <asm/io.h> +#include <asm/segment.h> +#include <asm/desc.h> +#include <asm/topology.h> #define __vsyscall(nr) __attribute__ ((unused,__section__(".vsyscall_" #nr))) int __sysctl_vsyscall __section_sysctl_vsyscall = 1; seqlock_t __xtime_lock __section_xtime_lock = SEQLOCK_UNLOCKED; +int __vgetcpu_mode __section_vgetcpu_mode; #include <asm/unistd.h> @@ -127,9 +132,46 @@ time_t __vsyscall(1) vtime(time_t *t) return __xtime.tv_sec; } -long __vsyscall(2) venosys_0(void) +/* Fast way to get current CPU and node. + This helps to do per node and per CPU caches in user space. + The result is not guaranteed without CPU affinity, but usually + works out because the scheduler tries to keep a thread on the same + CPU. + + tcache must point to a two element sized long array. + All arguments can be NULL. */ +long __vsyscall(2) +vgetcpu(unsigned *cpu, unsigned *node, struct getcpu_cache *tcache) { - return -ENOSYS; + unsigned int dummy, p; + unsigned long j = 0; + + /* Fast cache - only recompute value once per jiffies and avoid + relatively costly rdtscp/cpuid otherwise. + This works because the scheduler usually keeps the process + on the same CPU and this syscall doesn't guarantee its + results anyways. + We do this here because otherwise user space would do it on + its own in a likely inferior way (no access to jiffies). + If you don't like it pass NULL. */ + if (tcache && tcache->t0 == (j = __jiffies)) { + p = tcache->t1; + } else if (__vgetcpu_mode == VGETCPU_RDTSCP) { + /* Load per CPU data from RDTSCP */ + rdtscp(dummy, dummy, p); + } else { + /* Load per CPU data from GDT */ + asm("lsl %1,%0" : "=r" (p) : "r" (__PER_CPU_SEG)); + } + if (tcache) { + tcache->t0 = j; + tcache->t1 = p; + } + if (cpu) + *cpu = p & 0xfff; + if (node) + *node = p >> 12; + return 0; } long __vsyscall(3) venosys_1(void) @@ -200,6 +242,43 @@ static ctl_table kernel_root_table2[] = { #endif +static void __cpuinit write_rdtscp_cb(void *info) +{ + write_rdtscp_aux((unsigned long)info); +} + +void __cpuinit vsyscall_set_cpu(int cpu) +{ + unsigned long *d; + unsigned long node = 0; +#ifdef CONFIG_NUMA + node = cpu_to_node[cpu]; +#endif + if (cpu_has(&cpu_data[cpu], X86_FEATURE_RDTSCP)) { + void *info = (void *)((node << 12) | cpu); + /* Can happen on preemptive kernel */ + if (get_cpu() == cpu) + write_rdtscp_cb(info); +#ifdef CONFIG_SMP + else { + /* the notifier is unfortunately not executed on the + target CPU */ + smp_call_function_single(cpu,write_rdtscp_cb,info,0,1); + } +#endif + put_cpu(); + } + + /* Store cpu number in limit so that it can be loaded quickly + in user space in vgetcpu. + 12 bits for the CPU and 8 bits for the node. */ + d = (unsigned long *)(cpu_gdt(cpu) + GDT_ENTRY_PER_CPU); + *d = 0x0f40000000000ULL; + *d |= cpu; + *d |= (node & 0xf) << 12; + *d |= (node >> 4) << 48; +} + static void __init map_vsyscall(void) { extern char __vsyscall_0; @@ -214,6 +293,7 @@ static int __init vsyscall_init(void) VSYSCALL_ADDR(__NR_vgettimeofday))); BUG_ON((unsigned long) &vtime != VSYSCALL_ADDR(__NR_vtime)); BUG_ON((VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE))); + BUG_ON((unsigned long) &vgetcpu != VSYSCALL_ADDR(__NR_vgetcpu)); map_vsyscall(); #ifdef CONFIG_SYSCTL register_sysctl_table(kernel_root_table2, 0); |