Re: [Xen-devel] [PATCH 2/3] x86/svm: add EFER SVME support for VGIF/VLOAD

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 31.01.18 at 21:35, <brian.woods@xxxxxxx> wrote:
> Only enable virtual VMLOAD/SAVE and VGIF if the guest EFER.SVME is set.
> 
> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Brian Woods <brian.woods@xxxxxxx>
> ---
>  xen/arch/x86/hvm/svm/svm.c  | 69 
> +++++++++++++++++++++++++++++++++++++++++++++
>  xen/arch/x86/hvm/svm/vmcb.c | 17 -----------
>  2 files changed, 69 insertions(+), 17 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
> index c48fdfaa5d..7864ee39ae 100644
> --- a/xen/arch/x86/hvm/svm/svm.c
> +++ b/xen/arch/x86/hvm/svm/svm.c
> @@ -601,6 +601,73 @@ void svm_update_guest_cr(struct vcpu *v, unsigned int cr)
>      }
>  }
>  
> +/*
> + * This runs on EFER change to see if nested features need to either be
> + * turned off or on.
> + */
> +static void svm_nested_features_on_efer_update(struct vcpu *v)
> +{
> +    struct vmcb_struct *vmcb = v->arch.hvm_svm.vmcb;
> +    struct nestedsvm *svm = &vcpu_nestedsvm(v);
> +    u32 general2_intercepts;
> +    vintr_t vintr;
> +
> +   /*
> +    * Need state for transfering the nested gif status so only write on
> +    * the hvm_vcpu EFER.SVME changing.
> +    */
> +    if ( (v->arch.hvm_vcpu.guest_efer & EFER_SVME) &&
> +         nestedhvm_enabled(v->domain))

If the latter check was moved to the caller, the whole function
would perhaps be better placed in nestedsvm.c?

> +    {
> +        if ( (vmcb->virt_ext.fields.vloadsave_enable == 0) &&

Can you please avoid "== 0" and "== 1" on boolean fields (even
if, like in the case here, the bitfield has u64 as underlying type,
which is sort of pointless)?

Jan


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