Re: [PATCH 3/5] kvm/svm: enhance mov DR intercept handler

[Avi Kivity <avi@redhat.com>]

On 12/07/2010 01:02 PM, Alexander Graf wrote:
> On 07.12.2010, at 11:59, Andre Przywara wrote:
>
> >  Newer SVM implementations provide the GPR number in the VMCB, so
> >  that the emulation path is no longer necesarry to handle debug
> >  register access intercepts. Implement the handling in svm.c and
> >  use it when the info is provided.
> >
> >  Signed-off-by: Andre Przywara<andre.przywara@amd.com>
> >  ---
> >  arch/x86/kvm/svm.c |   55 ++++++++++++++++++++++++++++++++++++---------------
> >  1 files changed, 39 insertions(+), 16 deletions(-)
> >
> >  diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> >  index b7233fd..369bd85 100644
> >  --- a/arch/x86/kvm/svm.c
> >  +++ b/arch/x86/kvm/svm.c
> >  @@ -2669,6 +2669,29 @@ static int cr0_write_interception(struct vcpu_svm *svm)
> >  	return r == EMULATE_DONE;
> >  }
> >
> >  +static int dr_interception(struct vcpu_svm *svm)
> >  +{
> >  +	int reg, dr;
> >  +	unsigned long val;
> >  +
> >  +	if (!boot_cpu_has(SVM_FEATURE_DECODE_ASSIST))
> >  +		return emulate_on_interception(svm);
>
> Wouldn't it be better to just change the entry in svm_exit_handlers if we detect that feature on init? No unnecessary branching then.
>

I'd rather make them const instead.  For something performance critical 
(unlike this) we can use static_cpu_has().

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