** Description changed:
[Impact]
Userspace reads of CNTVCT_EL0 are broken on HiSilicon D05 systems, which
breaks some applications such as OpenMPI.
[Test Case]
#include <sys/times.h>
#include <stdio.h>
int main(int argc, char *argv[])
{
- unsigned int freq;
- __asm__ __volatile__ ("mrs %0, CNTFRQ_EL0" : "=r" (freq));
- printf("freq %d\n",freq);
- return (int)freq;
+ unsigned int freq;
+ __asm__ __volatile__ ("mrs %0, CNTFRQ_EL0" : "=r" (freq));
+ printf("freq %d\n",freq);
+ return (int)freq;
}
==================================
gcc test.c test
./test
This will report an illegal instruction, but should print a frequency
value.
[Regression Risk]
The best way we can minimize risk is to verify on both a system that has an
errata handler for the timer (D05) and a system that doesn't. We should then be
exercising both code paths.
+
+ I have regression tested this, using the above test case, on the HP
+ m400, the QDT Centriq 2400, and a Cavium ThunderX CRB.
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https://bugs.launchpad.net/bugs/1688164
Title:
arm64: Add CNTFRQ_EL0 handler
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