On 02/09/2016 19:31, Luiz Capitulino wrote:
> On Fri, 2 Sep 2016 19:00:41 +0200
> Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
>> On 31/08/2016 19:05, Luiz Capitulino wrote:
>>> vcpu0: 18446742405270834952
>>> vcpu1: 18446742405270834952
>>> vcpu2: 18446742405270834952
>>> vcpu3: 18446742405270834952
>>>
>>> - We'll probably need to export the TSC multiplier too.
>>> However, I've been using only the TSC offset for now.
>>> So, let's get this merged first and do the TSC multiplier
>>> as a second step
>>
>> You'll need to export the number of fractional bits in the multiplier,
>> too. It's going to be a very simple patch, so please do everything now.
>
> I didn't want to expose the multiplier before testing our tracing
> procedure with it.
Exposing the multiplier should be independent of tracing. I can test it
for you.
Paolo
> So far we've been only using the TSC offset (and
> it works great). I don't even know if I have a machine around to
> test it, so it could take a bit.
>
>> arch/x86/kvm/x86.c is huge; please create a new file arch/x86/kvm/debugfs.c.
>
> Will do.
>
>>> Signed-off-by: Luiz Capitulino <lcapitulino@xxxxxxxxxx>
>>> ---
>>> arch/x86/include/asm/kvm_host.h | 1 +
>>> arch/x86/kvm/svm.c | 1 +
>>> arch/x86/kvm/vmx.c | 8 ++++++++
>>> arch/x86/kvm/x86.c | 30 ++++++++++++++++++++++++++++++
>>> 4 files changed, 40 insertions(+)
>>>
>>> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
>>> index 33ae3a4..5714bbd 100644
>>> --- a/arch/x86/include/asm/kvm_host.h
>>> +++ b/arch/x86/include/asm/kvm_host.h
>>> @@ -952,6 +952,7 @@ struct kvm_x86_ops {
>>> bool (*has_wbinvd_exit)(void);
>>>
>>> u64 (*read_tsc_offset)(struct kvm_vcpu *vcpu);
>>> + u64 (*read_cached_tsc_offset)(struct kvm_vcpu *vcpu);
>>> void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset);
>>>
>>> u64 (*read_l1_tsc)(struct kvm_vcpu *vcpu, u64 host_tsc);
>>> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
>>> index af523d8..c851477 100644
>>> --- a/arch/x86/kvm/svm.c
>>> +++ b/arch/x86/kvm/svm.c
>>> @@ -5065,6 +5065,7 @@ static struct kvm_x86_ops svm_x86_ops = {
>>> .has_wbinvd_exit = svm_has_wbinvd_exit,
>>>
>>> .read_tsc_offset = svm_read_tsc_offset,
>>> + .read_cached_tsc_offset = svm_read_tsc_offset,
>>> .write_tsc_offset = svm_write_tsc_offset,
>>> .adjust_tsc_offset_guest = svm_adjust_tsc_offset_guest,
>>> .read_l1_tsc = svm_read_l1_tsc,
>>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>>> index 5cede40..82dfe42 100644
>>> --- a/arch/x86/kvm/vmx.c
>>> +++ b/arch/x86/kvm/vmx.c
>>> @@ -616,6 +616,7 @@ struct vcpu_vmx {
>>> u64 hv_deadline_tsc;
>>>
>>> u64 current_tsc_ratio;
>>> + u64 cached_tsc_offset;
>>>
>>> bool guest_pkru_valid;
>>> u32 guest_pkru;
>>> @@ -2608,6 +2609,11 @@ static u64 vmx_read_tsc_offset(struct kvm_vcpu *vcpu)
>>> return vmcs_read64(TSC_OFFSET);
>>> }
>>>
>>> +static u64 vmx_read_cached_tsc_offset(struct kvm_vcpu *vcpu)
>>> +{
>>> + return to_vmx(vcpu)->cached_tsc_offset;
>>> +}
>>> +
>>> /*
>>> * writes 'offset' into guest's timestamp counter offset register
>>> */
>>> @@ -2632,6 +2638,7 @@ static void vmx_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
>>> vmcs_read64(TSC_OFFSET), offset);
>>> vmcs_write64(TSC_OFFSET, offset);
>>> }
>>> + to_vmx(vcpu)->cached_tsc_offset = offset;
>>> }
>>>
>>> static void vmx_adjust_tsc_offset_guest(struct kvm_vcpu *vcpu, s64 adjustment)
>>> @@ -11275,6 +11282,7 @@ static struct kvm_x86_ops vmx_x86_ops = {
>>> .has_wbinvd_exit = cpu_has_vmx_wbinvd_exit,
>>>
>>> .read_tsc_offset = vmx_read_tsc_offset,
>>> + .read_cached_tsc_offset = vmx_read_cached_tsc_offset,
>>> .write_tsc_offset = vmx_write_tsc_offset,
>>> .adjust_tsc_offset_guest = vmx_adjust_tsc_offset_guest,
>>> .read_l1_tsc = vmx_read_l1_tsc,
>>
>> You need to handle SVM as well. So you might as well simplify the code:
>
> SVM is handled:
>
> + .read_cached_tsc_offset = svm_read_tsc_offset,
>
>> - add a kvm_vcpu_write_tsc_offset wrapper for kvm_x86_ops->write_tsc_offset
>>
>> - add a tsc_offset field in struct kvm_vcpu_arch
>>
>> - replace kvm_x86_ops->read_tsc_offset with accesses to the new field
>
> Given that SVM is handled, you still want me to do this?
>
>> Then in a fifth patch export the TSC offset (and multiplier ;)) to
>> userspace.
>>
>> I'm not very happy about having a single file for all TSC offsets.
>> Creating subdirectories under the PID-FD per-VM directory would be nicer
>> in the long run.
>
> I think Steven would also prefer that, but some people raised the
> concern at KVM Forum that creating per vcpu dirs in debugfs may
> consume considerable memory for a system running several dozen
> if not hundreds of VMs. This concern seems valid to me, but I
> can do either way.
>
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