KVM_HYPERCALL

KVM_HYPERCALL

[Kumar, Venkat]

I am making a hypercall "kvm_hypercall0" with number 0 from a Linux guest. But I don't see the control coming to "handle_vmcall" or even "kvm_handle_exit". What could be the reason?

Thx,

Venkat

Re: KVM_HYPERCALL

[Avi Kivity]

Kumar, Venkat wrote:
> I am making a hypercall "kvm_hypercall0" with number 0 from a Linux guest. But I don't see the control coming to "handle_vmcall" or even "kvm_handle_exit". What could be the reason?
>   

No idea.  kvm_handle_exit() is called very frequently, even without 
hypercalls.  Are you sure you don't see it called?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

RE: KVM_HYPERCALL

[Kumar, Venkat]

Hi Avi - Yes the control is not coming to neither " kvm_handle_exit " nor "handle_vmcall" after the hypercall is made from the guest.
If I am not wrong, the "KVM_HYPERCALL" instruction is expected to work, isn't it?

Thx,

Venkat


-----Original Message-----
From: Avi Kivity [mailto:avi@redhat.com] 
Sent: Monday, May 18, 2009 1:56 AM
To: Kumar, Venkat
Cc: kvm@vger.kernel.org
Subject: Re: KVM_HYPERCALL

Kumar, Venkat wrote:
> I am making a hypercall "kvm_hypercall0" with number 0 from a Linux guest. But I don't see the control coming to "handle_vmcall" or even "kvm_handle_exit". What could be the reason?
>   

No idea.  kvm_handle_exit() is called very frequently, even without 
hypercalls.  Are you sure you don't see it called?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

Re: KVM_HYPERCALL

[Avi Kivity]

Kumar, Venkat wrote:
> Hi Avi - Yes the control is not coming to neither " kvm_handle_exit " nor "handle_vmcall" after the hypercall is made from the guest.
> If I am not wrong, the "KVM_HYPERCALL" instruction is expected to work, isn't it?
>   

Yes, it should.  Are you sure the guest is executing this instruction?

-- 
error compiling committee.c: too many arguments to function

RE: KVM_HYPERCALL

[Kumar, Venkat]

Ok. With KVM-85 it works. I was using KVM-84 earlier.

Thx,

Venkat


-----Original Message-----
From: Avi Kivity [mailto:avi@redhat.com] 
Sent: Monday, May 18, 2009 5:03 PM
To: Kumar, Venkat
Cc: kvm@vger.kernel.org
Subject: Re: KVM_HYPERCALL

Kumar, Venkat wrote:
> Hi Avi - Yes the control is not coming to neither " kvm_handle_exit " nor "handle_vmcall" after the hypercall is made from the guest.
> If I am not wrong, the "KVM_HYPERCALL" instruction is expected to work, isn't it?
>   

Yes, it should.  Are you sure the guest is executing this instruction?

-- 
error compiling committee.c: too many arguments to function

RE: KVM_HYPERCALL

[Kumar, Venkat]

Hi Avi - Yes the control is not coming to neither " kvm_handle_exit " nor "handle_vmcall" after the hypercall is made from the guest.
If I am not wrong, the "KVM_HYPERCALL" instruction is expected to work, isn't it?

Thx,

Venkat


-----Original Message-----
From: Avi Kivity [mailto:avi@redhat.com] 
Sent: Monday, May 18, 2009 1:56 AM
To: Kumar, Venkat
Cc: kvm@vger.kernel.org
Subject: Re: KVM_HYPERCALL

Kumar, Venkat wrote:
> I am making a hypercall "kvm_hypercall0" with number 0 from a Linux guest. But I don't see the control coming to "handle_vmcall" or even "kvm_handle_exit". What could be the reason?
>   

No idea.  kvm_handle_exit() is called very frequently, even without 
hypercalls.  Are you sure you don't see it called?

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

Re: KVM_HYPERCALL

[Gregory Haskins]

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Kumar, Venkat wrote:
> Hi Avi - Yes the control is not coming to neither " kvm_handle_exit " nor "handle_vmcall" after the hypercall is made from the guest.
> If I am not wrong, the "KVM_HYPERCALL" instruction is expected to work, isn't it?
>   

Hi Venkat,
  I have used this method of IO many times, so I can attest it does work
in general.   I suspect that there may be some issue in either the
configuration of your environment or perhaps your particular usage of it.

What version guest and host are you running?  Can you confirm that your
guest has the proper pv-ops support enabled?  If so, do you check the
cpuid for the presence of your HC feature (or at least check for the
presence of others if you are not explicitly advertising your own, like
MMU_OP).  See kvm_para_has_feature().  If that returns 'true' then you
at least know the hypercall patching has been performed on your guest.

-Greg



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