On 12/3/21 6:25 AM, Peter Zijlstra wrote:
On Wed, Dec 01, 2021 at 10:46:49AM +0800, zhenwei pi wrote:
Wrapper function x86_get_cpufreq_khz() to get frequency on a x86
platform, hide detailed implementation from proc routine.
Also export this function for the further use, a typical case is that
kvm module gets the frequency of the host and tell the guest side by
kvmclock.
This function was already complete crap, and now you want to export it,
*WHY* ?!
What possible use does KVM have for this random number generator?
A KVM guest overwrites the '.calibrate_tsc' and '.calibrate_cpu' if
kvmclock is supported:
in function kvmclock_init(void) (linux/arch/x86/kernel/kvmclock.c)
...
x86_platform.calibrate_tsc = kvm_get_tsc_khz;
x86_platform.calibrate_cpu = kvm_get_tsc_khz;
...
And kvm_get_tsc_khz reads PV data from host side. Before guest reads
this, KVM should writes the frequency into the PV data structure.
And the problem is that KVM gets tsc_khz directly without aperf/mperf
detection. So user may gets different frequency(cat /proc/cpuinfo) from
guest & host.
Or is that possible to export function 'aperfmperf_get_khz'?
--
zhenwei pi
