#GP when trying to disengage Intel Dynamic Acceleration Technology

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NathanLAAS
Posts: 9
Joined: Fri Mar 14, 2025 1:58 am

#GP when trying to disengage Intel Dynamic Acceleration Technology

Post by NathanLAAS »

I'm writing an efi app, and as per Intel's documentation, disabling Intel Dynamic Accemeration Technology should be done with:
System software can temporarily disengage opportunistic processor performance operation by setting bit 32 of the
IA32_PERF_CTL MSR (0199H), using a read-modify-write sequence on the MSR.
However, doing

Code: Select all 

#define IA32_PERF_CTL 0x00000199
 uint32_t a, d;
 asm volatile (
 "rdmsr\n\t"
 "or 0ドルx1, %%edx\n\t"
 "wrmsr\n\t"
 : "=a" (a), "=d" (d) : "c" (IA32_PERF_CTL)
 );
result in a #GP.
I haven't seen any prerequisites that need to be ensured before writing to IA32_PERF_CTL, am I missing something resulting in this #GP?
Octocontrabass
Member
Member
Posts: 5968
Joined: Mon Mar 25, 2013 7:01 pm

Re: #GP when trying to disengage Intel Dynamic Acceleration Technology

Post by Octocontrabass »

Did you check CPUID to make sure your CPU supports Dynamic Acceleration?
NathanLAAS
Posts: 9
Joined: Fri Mar 14, 2025 1:58 am

Re: #GP when trying to disengage Intel Dynamic Acceleration Technology

Post by NathanLAAS »

My bad, it seems to be that my CPU does not support IDA, I was too fast to ask lol
As I'm trying to remove any feature that could lead to DVFS and still have some I thought of IDA as the highest probable feature that does such a thing without thinking whether is was possible on my CPU or not.
Thanks for your help!
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