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/*
* cacheinfo.c - helpers to query the host about its caches
*
* Copyright (C) 2017, Emilio G. Cota <cota@braap.org>
* License: GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qemu/host-utils.h"
#include "qemu/atomic.h"
int qemu_icache_linesize = 0;
int qemu_icache_linesize_log;
int qemu_dcache_linesize = 0;
int qemu_dcache_linesize_log;
/*
* Operating system specific detection mechanisms.
*/
#if defined(_WIN32)
static void sys_cache_info(int *isize, int *dsize)
{
SYSTEM_LOGICAL_PROCESSOR_INFORMATION *buf;
DWORD size = 0;
BOOL success;
size_t i, n;
/* Check for the required buffer size first. Note that if the zero
size we use for the probe results in success, then there is no
data available; fail in that case. */
success = GetLogicalProcessorInformation(0, &size);
if (success || GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
return;
}
n = size / sizeof(SYSTEM_LOGICAL_PROCESSOR_INFORMATION);
size = n * sizeof(SYSTEM_LOGICAL_PROCESSOR_INFORMATION);
buf = g_new0(SYSTEM_LOGICAL_PROCESSOR_INFORMATION, n);
if (!GetLogicalProcessorInformation(buf, &size)) {
goto fail;
}
for (i = 0; i < n; i++) {
if (buf[i].Relationship == RelationCache
&& buf[i].Cache.Level == 1) {
switch (buf[i].Cache.Type) {
case CacheUnified:
*isize = *dsize = buf[i].Cache.LineSize;
break;
case CacheInstruction:
*isize = buf[i].Cache.LineSize;
break;
case CacheData:
*dsize = buf[i].Cache.LineSize;
break;
default:
break;
}
}
}
fail:
g_free(buf);
}
#elif defined(__APPLE__)
# include <sys/sysctl.h>
static void sys_cache_info(int *isize, int *dsize)
{
/* There's only a single sysctl for both I/D cache line sizes. */
long size;
size_t len = sizeof(size);
if (!sysctlbyname("hw.cachelinesize", &size, &len, NULL, 0)) {
*isize = *dsize = size;
}
}
#elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
# include <sys/sysctl.h>
static void sys_cache_info(int *isize, int *dsize)
{
/* There's only a single sysctl for both I/D cache line sizes. */
int size;
size_t len = sizeof(size);
if (!sysctlbyname("machdep.cacheline_size", &size, &len, NULL, 0)) {
*isize = *dsize = size;
}
}
#else
/* POSIX */
static void sys_cache_info(int *isize, int *dsize)
{
# ifdef _SC_LEVEL1_ICACHE_LINESIZE
*isize = sysconf(_SC_LEVEL1_ICACHE_LINESIZE);
# endif
# ifdef _SC_LEVEL1_DCACHE_LINESIZE
*dsize = sysconf(_SC_LEVEL1_DCACHE_LINESIZE);
# endif
}
#endif /* sys_cache_info */
/*
* Architecture (+ OS) specific detection mechanisms.
*/
#if defined(__aarch64__)
static void arch_cache_info(int *isize, int *dsize)
{
if (*isize == 0 || *dsize == 0) {
uint64_t ctr;
/* The real cache geometry is in CCSIDR_EL1/CLIDR_EL1/CSSELR_EL1,
but (at least under Linux) these are marked protected by the
kernel. However, CTR_EL0 contains the minimum linesize in the
entire hierarchy, and is used by userspace cache flushing. */
asm volatile("mrs\t%0, ctr_el0" : "=r"(ctr));
if (*isize == 0) {
*isize = 4 << (ctr & 0xf);
}
if (*dsize == 0) {
*dsize = 4 << ((ctr >> 16) & 0xf);
}
}
}
#elif defined(_ARCH_PPC) && defined(__linux__)
# include "elf.h"
static void arch_cache_info(int *isize, int *dsize)
{
if (*isize == 0) {
*isize = qemu_getauxval(AT_ICACHEBSIZE);
}
if (*dsize == 0) {
*dsize = qemu_getauxval(AT_DCACHEBSIZE);
}
}
#else
static void arch_cache_info(int *isize, int *dsize) { }
#endif /* arch_cache_info */
/*
* ... and if all else fails ...
*/
static void fallback_cache_info(int *isize, int *dsize)
{
/* If we can only find one of the two, assume they're the same. */
if (*isize) {
if (*dsize) {
/* Success! */
} else {
*dsize = *isize;
}
} else if (*dsize) {
*isize = *dsize;
} else {
#if defined(_ARCH_PPC)
/* For PPC, we're going to use the icache size computed for
flush_icache_range. Which means that we must use the
architecture minimum. */
*isize = *dsize = 16;
#else
/* Otherwise, 64 bytes is not uncommon. */
*isize = *dsize = 64;
#endif
}
}
static void __attribute__((constructor)) init_cache_info(void)
{
int isize = 0, dsize = 0;
sys_cache_info(&isize, &dsize);
arch_cache_info(&isize, &dsize);
fallback_cache_info(&isize, &dsize);
assert((isize & (isize - 1)) == 0);
assert((dsize & (dsize - 1)) == 0);
qemu_icache_linesize = isize;
qemu_icache_linesize_log = ctz32(isize);
qemu_dcache_linesize = dsize;
qemu_dcache_linesize_log = ctz32(dsize);
atomic64_init();
}
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