util/cacheinfo.c

   1 /*
   2  * cacheinfo.c - helpers to query the host about its caches
   3  *
   4  * Copyright (C) 2017, Emilio G. Cota <cota@braap.org>
   5  * License: GNU GPL, version 2 or later.
   6  *   See the COPYING file in the top-level directory.
   7  */
   8
   9 #include "qemu/osdep.h"
  10 #include "qemu/host-utils.h"
  11 #include "qemu/atomic.h"
  12
  13 int qemu_icache_linesize = 0;
  14 int qemu_icache_linesize_log;
  15 int qemu_dcache_linesize = 0;
  16 int qemu_dcache_linesize_log;
  17
  18 /*
  19  * Operating system specific detection mechanisms.
  20  */
  21
  22 #if defined(_WIN32)
  23
  24 static void sys_cache_info(int *isize, int *dsize)
  25 {
  26     SYSTEM_LOGICAL_PROCESSOR_INFORMATION *buf;
  27     DWORD size = 0;
  28     BOOL success;
  29     size_t i, n;
  30
  31     /* Check for the required buffer size first.  Note that if the zero
  32        size we use for the probe results in success, then there is no
  33        data available; fail in that case.  */
  34     success = GetLogicalProcessorInformation(0, &size);
  35     if (success || GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
  36         return;
  37     }
  38
  39     n = size / sizeof(SYSTEM_LOGICAL_PROCESSOR_INFORMATION);
  40     size = n * sizeof(SYSTEM_LOGICAL_PROCESSOR_INFORMATION);
  41     buf = g_new0(SYSTEM_LOGICAL_PROCESSOR_INFORMATION, n);
  42     if (!GetLogicalProcessorInformation(buf, &size)) {
  43         goto fail;
  44     }
  45
  46     for (i = 0; i < n; i++) {
  47         if (buf[i].Relationship == RelationCache
  48             && buf[i].Cache.Level == 1) {
  49             switch (buf[i].Cache.Type) {
  50             case CacheUnified:
  51                 *isize = *dsize = buf[i].Cache.LineSize;
  52                 break;
  53             case CacheInstruction:
  54                 *isize = buf[i].Cache.LineSize;
  55                 break;
  56             case CacheData:
  57                 *dsize = buf[i].Cache.LineSize;
  58                 break;
  59             default:
  60                 break;
  61             }
  62         }
  63     }
  64  fail:
  65     g_free(buf);
  66 }
  67
  68 #elif defined(__APPLE__)
  69 # include <sys/sysctl.h>
  70 static void sys_cache_info(int *isize, int *dsize)
  71 {
  72     /* There's only a single sysctl for both I/D cache line sizes.  */
  73     long size;
  74     size_t len = sizeof(size);
  75     if (!sysctlbyname("hw.cachelinesize", &size, &len, NULL, 0)) {
  76         *isize = *dsize = size;
  77     }
  78 }
  79 #elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
  80 # include <sys/sysctl.h>
  81 static void sys_cache_info(int *isize, int *dsize)
  82 {
  83     /* There's only a single sysctl for both I/D cache line sizes.  */
  84     int size;
  85     size_t len = sizeof(size);
  86     if (!sysctlbyname("machdep.cacheline_size", &size, &len, NULL, 0)) {
  87         *isize = *dsize = size;
  88     }
  89 }
  90 #else
  91 /* POSIX */
  92
  93 static void sys_cache_info(int *isize, int *dsize)
  94 {
  95 # ifdef _SC_LEVEL1_ICACHE_LINESIZE
  96     int tmp_isize = (int) sysconf(_SC_LEVEL1_ICACHE_LINESIZE);
  97     if (tmp_isize > 0) {
  98         *isize = tmp_isize;
  99     }
 100 # endif
 101 # ifdef _SC_LEVEL1_DCACHE_LINESIZE
 102     int tmp_dsize = (int) sysconf(_SC_LEVEL1_DCACHE_LINESIZE);
 103     if (tmp_dsize > 0) {
 104         *dsize = tmp_dsize;
 105     }
 106 # endif
 107 }
 108 #endif /* sys_cache_info */
 109
 110 /*
 111  * Architecture (+ OS) specific detection mechanisms.
 112  */
 113
 114 #if defined(__aarch64__)
 115
 116 static void arch_cache_info(int *isize, int *dsize)
 117 {
 118     if (*isize == 0 || *dsize == 0) {
 119         uint64_t ctr;
 120
 121         /* The real cache geometry is in CCSIDR_EL1/CLIDR_EL1/CSSELR_EL1,
 122            but (at least under Linux) these are marked protected by the
 123            kernel.  However, CTR_EL0 contains the minimum linesize in the
 124            entire hierarchy, and is used by userspace cache flushing.  */
 125         asm volatile("mrs\t%0, ctr_el0" : "=r"(ctr));
 126         if (*isize == 0) {
 127             *isize = 4 << (ctr & 0xf);
 128         }
 129         if (*dsize == 0) {
 130             *dsize = 4 << ((ctr >> 16) & 0xf);
 131         }
 132     }
 133 }
 134
 135 #elif defined(_ARCH_PPC) && defined(__linux__)
 136 # include "elf.h"
 137
 138 static void arch_cache_info(int *isize, int *dsize)
 139 {
 140     if (*isize == 0) {
 141         *isize = qemu_getauxval(AT_ICACHEBSIZE);
 142     }
 143     if (*dsize == 0) {
 144         *dsize = qemu_getauxval(AT_DCACHEBSIZE);
 145     }
 146 }
 147
 148 #else
 149 static void arch_cache_info(int *isize, int *dsize) { }
 150 #endif /* arch_cache_info */
 151
 152 /*
 153  * ... and if all else fails ...
 154  */
 155
 156 static void fallback_cache_info(int *isize, int *dsize)
 157 {
 158     /* If we can only find one of the two, assume they're the same.  */
 159     if (*isize) {
 160         if (*dsize) {
 161             /* Success! */
 162         } else {
 163             *dsize = *isize;
 164         }
 165     } else if (*dsize) {
 166         *isize = *dsize;
 167     } else {
 168 #if defined(_ARCH_PPC)
 169         /* For PPC, we're going to use the icache size computed for
 170            flush_icache_range.  Which means that we must use the
 171            architecture minimum.  */
 172         *isize = *dsize = 16;
 173 #else
 174         /* Otherwise, 64 bytes is not uncommon.  */
 175         *isize = *dsize = 64;
 176 #endif
 177     }
 178 }
 179
 180 static void __attribute__((constructor)) init_cache_info(void)
 181 {
 182     int isize = 0, dsize = 0;
 183
 184     sys_cache_info(&isize, &dsize);
 185     arch_cache_info(&isize, &dsize);
 186     fallback_cache_info(&isize, &dsize);
 187
 188     assert((isize & (isize - 1)) == 0);
 189     assert((dsize & (dsize - 1)) == 0);
 190
 191     qemu_icache_linesize = isize;
 192     qemu_icache_linesize_log = ctz32(isize);
 193     qemu_dcache_linesize = dsize;
 194     qemu_dcache_linesize_log = ctz32(dsize);
 195
 196     qatomic64_init();
 197 }