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Provide deterministic (and somewhat useful) value for RDPID result,

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and for %ecx after RDTSCP.

Initialize TSC_AUX MSR with CPUID.  It allows for userspace to cheaply
identify CPU it was executed on some time ago, which is sometimes useful.

Note: The values returned might be changed in future.

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2019-03-15 16:43:28 +00:00
parent 7e0a345bc5
commit 39d70f6b80
2 changed files with 7 additions and 0 deletions
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4
sys/amd64/amd64/initcpu.c
View File

@ -265,6 +265,10 @@ initializecpu(void)
init_via();
break;
}
if ((amd_feature & AMDID_RDTSCP) != 0 ||
(cpu_stdext_feature2 & CPUID_STDEXT2_RDPID) != 0)
wrmsr(MSR_TSC_AUX, PCPU_GET(cpuid));
}
void

3
sys/i386/i386/initcpu.c
View File

@ -749,6 +749,9 @@ initializecpu(void)
msr = rdmsr(MSR_EFER) | EFER_NXE;
wrmsr(MSR_EFER, msr);
}
if ((amd_feature & AMDID_RDTSCP) != 0 ||
(cpu_stdext_feature2 & CPUID_STDEXT2_RDPID) != 0)
wrmsr(MSR_TSC_AUX, PCPU_GET(cpuid));
}
void