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

Alexander Graf
2010-12-07T11:03:03Z

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.

Alex