On 04/11/2015 20:33, Gerhard Wiesinger wrote:
> Signed-off-by: Gerhard Wiesinger <lists@xxxxxxxxxxxxx>
> ---
> arch/x86/kvm/svm.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 2f9ed1f..e0b00fc 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -198,6 +198,10 @@ static bool npt_enabled;
> static int npt = true;
> module_param(npt, int, S_IRUGO);
> +/* allow backward compatibility with e.g. old DOS application */
> +static int npt_task_switch_emulation = true;
> +module_param(npt_task_switch_emulation, int, S_IRUGO);
> +
> /* allow nested virtualization in KVM/SVM */
> static int nested = true;
> module_param(nested, int, S_IRUGO);
> @@ -1177,6 +1181,9 @@ static void init_vmcb(struct vcpu_svm *svm, bool
> init_event)
> if (npt_enabled) {
> /* Setup VMCB for Nested Paging */
> control->nested_ctl = 1;
> + if (!npt_task_switch_emulation) {
> + clr_intercept(svm, INTERCEPT_TASK_SWITCH);
> + }
> clr_intercept(svm, INTERCEPT_INVLPG);
> clr_exception_intercept(svm, PF_VECTOR);
> clr_cr_intercept(svm, INTERCEPT_CR3_READ);
What is the problem you are seeing? KVM can emulate task switches; the
intercept is set here because of a processor erratum that can mess them
up even though, in theory, AMD supports task switching from guest mode.
Paolo
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