* [PATCH] x86/vmware: avoid TSC recalibration
@ 2021-01-05 0:47 Alexey Makhalov
2021-01-05 13:06 ` Vitaly Kuznetsov
0 siblings, 1 reply; 3+ messages in thread
From: Alexey Makhalov @ 2021-01-05 0:47 UTC (permalink / raw)
To: linux-kernel, virtualization, hpa, bp, mingo, tglx, pv-drivers, sdeep
Cc: Alexey Makhalov
When TSC frequency is known (retrieved from hypervisor), we should skip
TSC refined calibration by setting X86_FEATURE_TSC_KNOWN_FREQ.
Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
---
arch/x86/kernel/cpu/vmware.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
index c6ede3b3d302..83164110ccc5 100644
--- a/arch/x86/kernel/cpu/vmware.c
+++ b/arch/x86/kernel/cpu/vmware.c
@@ -378,6 +378,8 @@ static void __init vmware_set_capabilities(void)
{
setup_force_cpu_cap(X86_FEATURE_CONSTANT_TSC);
setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
+ if (vmware_tsc_khz)
+ setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMCALL)
setup_force_cpu_cap(X86_FEATURE_VMCALL);
else if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMMCALL)
--
2.11.0
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^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] x86/vmware: avoid TSC recalibration
2021-01-05 0:47 [PATCH] x86/vmware: avoid TSC recalibration Alexey Makhalov
@ 2021-01-05 13:06 ` Vitaly Kuznetsov
2021-03-15 22:24 ` Alexey Makhalov
0 siblings, 1 reply; 3+ messages in thread
From: Vitaly Kuznetsov @ 2021-01-05 13:06 UTC (permalink / raw)
To: Alexey Makhalov
Cc: pv-drivers, linux-kernel, virtualization, mingo, bp, hpa, tglx
Alexey Makhalov <amakhalov@vmware.com> writes:
> When TSC frequency is known (retrieved from hypervisor), we should skip
> TSC refined calibration by setting X86_FEATURE_TSC_KNOWN_FREQ.
>
> Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
> ---
> arch/x86/kernel/cpu/vmware.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
> index c6ede3b3d302..83164110ccc5 100644
> --- a/arch/x86/kernel/cpu/vmware.c
> +++ b/arch/x86/kernel/cpu/vmware.c
> @@ -378,6 +378,8 @@ static void __init vmware_set_capabilities(void)
> {
> setup_force_cpu_cap(X86_FEATURE_CONSTANT_TSC);
> setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
> + if (vmware_tsc_khz)
> + setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
> if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMCALL)
> setup_force_cpu_cap(X86_FEATURE_VMCALL);
> else if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMMCALL)
The same trick is being used in Xen/Jailhouse/KVM code already and
Hyper-V overwrites x86_platform.calibrate_tsc/x86_platform.calibrate_cpu
hooks to basically achive the same goal. Should we maybe introduce a
flag in 'struct hypervisor_x86' or something like that to unify all
this?
Just a suggestion.
--
Vitaly
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] x86/vmware: avoid TSC recalibration
2021-01-05 13:06 ` Vitaly Kuznetsov
@ 2021-03-15 22:24 ` Alexey Makhalov
0 siblings, 0 replies; 3+ messages in thread
From: Alexey Makhalov @ 2021-03-15 22:24 UTC (permalink / raw)
To: Vitaly Kuznetsov
Cc: pv-drivers, linux-kernel, virtualization, mingo, Borislav Petkov,
H . Peter Anvin, tglx
Hi Vitaly,
I believe, it is responsibility of each guest code to set X86_FEATURE_TSC_KNOWN_FREQ cap.
Regarding VMware guest, there is a case where vmware_tsc_khz is zero (not provided by hypervisor)
and TSC frequency should be calculated.
Sorry for late response.
Regards,
—Alexey
> On Jan 5, 2021, at 5:06 AM, Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>
> Alexey Makhalov <amakhalov@vmware.com> writes:
>
>> When TSC frequency is known (retrieved from hypervisor), we should skip
>> TSC refined calibration by setting X86_FEATURE_TSC_KNOWN_FREQ.
>>
>> Signed-off-by: Alexey Makhalov <amakhalov@vmware.com>
>> ---
>> arch/x86/kernel/cpu/vmware.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/arch/x86/kernel/cpu/vmware.c b/arch/x86/kernel/cpu/vmware.c
>> index c6ede3b3d302..83164110ccc5 100644
>> --- a/arch/x86/kernel/cpu/vmware.c
>> +++ b/arch/x86/kernel/cpu/vmware.c
>> @@ -378,6 +378,8 @@ static void __init vmware_set_capabilities(void)
>> {
>> setup_force_cpu_cap(X86_FEATURE_CONSTANT_TSC);
>> setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
>> + if (vmware_tsc_khz)
>> + setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
>> if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMCALL)
>> setup_force_cpu_cap(X86_FEATURE_VMCALL);
>> else if (vmware_hypercall_mode == CPUID_VMWARE_FEATURES_ECX_VMMCALL)
>
> The same trick is being used in Xen/Jailhouse/KVM code already and
> Hyper-V overwrites x86_platform.calibrate_tsc/x86_platform.calibrate_cpu
> hooks to basically achive the same goal. Should we maybe introduce a
> flag in 'struct hypervisor_x86' or something like that to unify all
> this?
>
> Just a suggestion.
>
> --
> Vitaly
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2021-01-05 0:47 [PATCH] x86/vmware: avoid TSC recalibration Alexey Makhalov
2021-01-05 13:06 ` Vitaly Kuznetsov
2021-03-15 22:24 ` Alexey Makhalov
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