Re: [PATCH v3 6/8] nSVM: introduce struct vmcb_ctrl_area_cached

Maxim Levitsky
2021-10-22T14:49:57Z

On Mon, 2021-10-11 at 10:37 -0400, Emanuele Giuseppe Esposito wrote:
> This structure will replace vmcb_control_area in
> svm_nested_state, providing only the fields that are actually
> used by the nested state. This avoids having and copying around
> uninitialized fields. The cost of this, however, is that all
> functions (in this case vmcb_is_intercept) expect the old
> structure, so they need to be duplicated.
>
> Introduce also nested_copy_vmcb_cache_to_control(), useful to copy
> vmcb_ctrl_area_cached fields in vmcb_control_area. This will
> be used in the next patch.
>
> Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
> ---
> arch/x86/kvm/svm/nested.c | 32 ++++++++++++++++++++++++++++++++
> arch/x86/kvm/svm/svm.h | 31 +++++++++++++++++++++++++++++++
> 2 files changed, 63 insertions(+)
>
> diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
> index e08f2c31beae..c84cded1dcf6 100644
> --- a/arch/x86/kvm/svm/nested.c
> +++ b/arch/x86/kvm/svm/nested.c
> @@ -1213,6 +1213,38 @@ int nested_svm_exit_special(struct vcpu_svm *svm)
> return NESTED_EXIT_CONTINUE;
> }
>
> +/* Inverse operation of nested_copy_vmcb_control_to_cache(). asid is copied too. */
> +static void nested_copy_vmcb_cache_to_control(struct vmcb_control_area *dst,
> + struct vmcb_ctrl_area_cached *from)
> +{
> + unsigned int i;
> +
> + for (i = 0; i < MAX_INTERCEPT; i++)
> + dst->intercepts[i] = from->intercepts[i];
> +
> + dst->iopm_base_pa = from->iopm_base_pa;
> + dst->msrpm_base_pa = from->msrpm_base_pa;
> + dst->tsc_offset = from->tsc_offset;
> + dst->asid = from->asid;
> + dst->tlb_ctl = from->tlb_ctl;
> + dst->int_ctl = from->int_ctl;
> + dst->int_vector = from->int_vector;
> + dst->int_state = from->int_state;
> + dst->exit_code = from->exit_code;
> + dst->exit_code_hi = from->exit_code_hi;
> + dst->exit_info_1 = from->exit_info_1;
> + dst->exit_info_2 = from->exit_info_2;
> + dst->exit_int_info = from->exit_int_info;
> + dst->exit_int_info_err = from->exit_int_info_err;
> + dst->nested_ctl = from->nested_ctl;
> + dst->event_inj = from->event_inj;
> + dst->event_inj_err = from->event_inj_err;
> + dst->nested_cr3 = from->nested_cr3;
> + dst->virt_ext = from->virt_ext;
> + dst->pause_filter_count = from->pause_filter_count;
> + dst->pause_filter_thresh = from->pause_filter_thresh;
> +}

Nitpick: Just in case I would 'memset to zero' the dst, to avoid potentionally having undefined values
in fields which we don't copy.

> +
> static int svm_get_nested_state(struct kvm_vcpu *vcpu,
> struct kvm_nested_state __user *user_kvm_nested_state,
> u32 user_data_size)
> diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
> index 3c950aeca646..78006245e334 100644
> --- a/arch/x86/kvm/svm/svm.h
> +++ b/arch/x86/kvm/svm/svm.h
> @@ -116,6 +116,31 @@ struct vmcb_save_area_cached {
> u64 dr6;
> };
>
> +struct vmcb_ctrl_area_cached {
> + u32 intercepts[MAX_INTERCEPT];
> + u16 pause_filter_thresh;
> + u16 pause_filter_count;
> + u64 iopm_base_pa;
> + u64 msrpm_base_pa;
> + u64 tsc_offset;
> + u32 asid;
> + u8 tlb_ctl;
> + u32 int_ctl;
> + u32 int_vector;
> + u32 int_state;
> + u32 exit_code;
> + u32 exit_code_hi;
> + u64 exit_info_1;
> + u64 exit_info_2;
> + u32 exit_int_info;
> + u32 exit_int_info_err;
> + u64 nested_ctl;
> + u32 event_inj;
> + u32 event_inj_err;
> + u64 nested_cr3;
> + u64 virt_ext;
> +};

This looks great.

> +
> struct svm_nested_state {
> struct kvm_vmcb_info vmcb02;
> u64 hsave_msr;
> @@ -308,6 +333,12 @@ static inline bool vmcb_is_intercept(struct vmcb_control_area *control, u32 bit)
> return test_bit(bit, (unsigned long *)&control->intercepts);
> }
>
> +static inline bool vmcb12_is_intercept(struct vmcb_ctrl_area_cached *control, u32 bit)
> +{
> + WARN_ON_ONCE(bit >= 32 * MAX_INTERCEPT);
> + return test_bit(bit, (unsigned long *)&control->intercepts);
> +}
> +
> static inline void set_dr_intercepts(struct vcpu_svm *svm)
> {
> struct vmcb *vmcb = svm->vmcb01.ptr;

So other than the nitpick:

Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

Best regards,
Maxim Levitsky