On 12/2/21 10:48 AM, Thomas Gleixner wrote:
On Wed, Dec 01 2021 at 10:46, zhenwei pi wrote:
If the host side supports APERF&MPERF feature, the guest side may get
mismatched frequency.
KVM uses x86_get_cpufreq_khz() to get the same frequency for guest side.
Signed-off-by: zhenwei pi <pizhenwei@xxxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5a403d92833f..125ed3c8b21a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8305,10 +8305,8 @@ static void tsc_khz_changed(void *data)
if (data)
khz = freq->new;
- else if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC))
- khz = cpufreq_quick_get(raw_smp_processor_id());
if (!khz)
- khz = tsc_khz;
+ khz = x86_get_cpufreq_khz(raw_smp_processor_id());
my brain compiler tells me that this is broken.
Without this patch:
1, boot_cpu_has(X86_FEATURE_CONSTANT_TSC) is true:
no kvmclock_cpufreq_notifier, and khz = tsc_khz;
2, boot_cpu_has(X86_FEATURE_CONSTANT_TSC) is false:
during installing kmod, try cpufreq_quick_get(), or use tsc_khz;
and get changed by kvmclock_cpufreq_notifier.
With this patch:
1, boot_cpu_has(X86_FEATURE_CONSTANT_TSC) is true:
no kvmclock_cpufreq_notifier, try aperf/mperf, or try
cpufreq_quick_get(), or use cpu_khz
2, boot_cpu_has(X86_FEATURE_CONSTANT_TSC) is false:
during installing kmod, try aperf/mperf, or try cpufreq_quick_get(), or
use cpu_khz;
and get changed by kvmclock_cpufreq_notifier.
I tested on Skylake&Icelake CPU, and got different CPU frequency from
host & guest, the main purpose of this patch is to get the same frequency.
--
zhenwei pi
