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util/cpuinfo-riscv: Use linux __riscv_hwprobe syscall 

With recent linux kernels, there is a syscall to probe for various
ISA extensions.  These bits were phased in over several kernel
releases, so we still require checks for symbol availability.

Acked-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
This commit is contained in:
Richard Henderson 2024-06-27 17:36:43 +00:00
parent adc028428a
commit e57173085a
2 changed files with 32 additions and 0 deletions
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6
meson.build
View File

@ -2862,6 +2862,12 @@ have_cpuid_h = cc.links('''
}''')
config_host_data.set('CONFIG_CPUID_H', have_cpuid_h)
# Don't bother to advertise asm/hwprobe.h for old versions that do
# not contain RISCV_HWPROBE_EXT_ZBA.
config_host_data.set('CONFIG_ASM_HWPROBE_H',
cc.has_header_symbol('asm/hwprobe.h',
'RISCV_HWPROBE_EXT_ZBA'))
config_host_data.set('CONFIG_AVX2_OPT', get_option('avx2') \
.require(have_cpuid_h, error_message: 'cpuid.h not available, cannot enable AVX2') \
.require(cc.links('''

26
util/cpuinfo-riscv.c
View File

@ -6,6 +6,11 @@
#include "qemu/osdep.h"
#include "host/cpuinfo.h"
#ifdef CONFIG_ASM_HWPROBE_H
#include <asm/hwprobe.h>
#include <sys/syscall.h>
#endif
unsigned cpuinfo;
static volatile sig_atomic_t got_sigill;
@ -47,6 +52,27 @@ unsigned __attribute__((constructor)) cpuinfo_init(void)
#endif
left &= ~info;
#ifdef CONFIG_ASM_HWPROBE_H
if (left) {
/*
* TODO: glibc 2.40 will introduce <sys/hwprobe.h>, which
* provides __riscv_hwprobe and __riscv_hwprobe_one,
* which is a slightly cleaner interface.
*/
struct riscv_hwprobe pair = { .key = RISCV_HWPROBE_KEY_IMA_EXT_0 };
if (syscall(__NR_riscv_hwprobe, &pair, 1, 0, NULL, 0) == 0
&& pair.key >= 0) {
info |= pair.value & RISCV_HWPROBE_EXT_ZBA ? CPUINFO_ZBA : 0;
info |= pair.value & RISCV_HWPROBE_EXT_ZBB ? CPUINFO_ZBB : 0;
left &= ~(CPUINFO_ZBA | CPUINFO_ZBB);
#ifdef RISCV_HWPROBE_EXT_ZICOND
info |= pair.value & RISCV_HWPROBE_EXT_ZICOND ? CPUINFO_ZICOND : 0;
left &= ~CPUINFO_ZICOND;
#endif
}
}
#endif /* CONFIG_ASM_HWPROBE_H */
if (left) {
struct sigaction sa_old, sa_new;