How to Disable Hardware Prefetcher in Core I7

Correctly disable Hardware Prefetching with MSR in Skylake

I found that this commands are working correctly. sudo modprobe msr - should be executed first though. The main problem was the way I was testing it with papi events

How do I programmatically disable hardware prefetching?

From the Intel reference:

This instruction must be executed at privilege level 0 or in real-address mode; otherwise, a general protection exception #GP(0) will be generated. Specifying a reserved or unimplemented MSR address in ECX will also cause a general protection exception.

...

The CPUID instruction should be used to determine whether MSRs are supported (EDX[5]=1)
before using this instruction.

So, your fault might be related to a cpu that doesn't support MSRs or using the wrong MSR address.

There are lots of examples of using the MSRs in the kernel source:

In the kernel source, for a single cpu, it demonstrates disabling prefetch for the Xeon in arch/i386/kernel/cpu/intel.c, in the function:

static void __cpuinit Intel_errata_workarounds(struct cpuinfo_x86 *c)

The rdmsr function arguments are the msr number, a pointer to the low 32 bit word, and a pointer to the high 32 bit word.

The wrmsr function arguments are the msr number, the low 32 bit word value, and the high 32 bit word value.

multi-core or smp systems have to pass the cpu struct in as the first argument:

void rdmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 *l, u32 *h);

void wrmsr_on_cpu(unsigned int cpu, u32 msr_no, u32 l, u32 h);

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