On Fri, Aug 18, 2023 at 05:49:58AM -0400, Xiaoyao Li wrote:
> Bit 28 of TD attribute, named SEPT_VE_DISABLE. When set to 1, it disables
> EPT violation conversion to #VE on guest TD access of PENDING pages.
>
> Some guest OS (e.g., Linux TD guest) may require this bit as 1.
> Otherwise refuse to boot.
>
> Add sept-ve-disable property for tdx-guest object, for user to configure
> this bit.
>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> Acked-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> ---
> qapi/qom.json | 4 +++-
> target/i386/kvm/tdx.c | 24 ++++++++++++++++++++++++
> 2 files changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/qapi/qom.json b/qapi/qom.json
> index 2ca7ce7c0da5..cc08b9a98df9 100644
> --- a/qapi/qom.json
> +++ b/qapi/qom.json
> @@ -871,10 +871,12 @@
> #
> # Properties for tdx-guest objects.
> #
> +# @sept-ve-disable: bit 28 of TD attributes (default: 0)
This description isn't very useful as it forces the user to go off and
read the TDX specification to find out what bit 28 means. You've got a
more useful description in the commit message, so please use that
in the docs too. eg something like this
@sept-ve-disable: toggle bit 28 of TD attributes to control disabling
of EPT violation conversion to #VE on guest
TD access of PENDING pages. Some guest OS (e.g.
Linux TD guest) may require this set, otherwise
they refuse to boot.
> +#
> # Since: 8.2
> ##
> { 'struct': 'TdxGuestProperties',
> - 'data': { }}
> + 'data': { '*sept-ve-disable': 'bool' } }
>
> ##
> # @ThreadContextProperties:
> diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
> index 3d313ed46bd1..22130382c0c5 100644
> --- a/target/i386/kvm/tdx.c
> +++ b/target/i386/kvm/tdx.c
> @@ -32,6 +32,8 @@
> (1U << KVM_FEATURE_PV_SCHED_YIELD) | \
> (1U << KVM_FEATURE_MSI_EXT_DEST_ID))
>
> +#define TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE BIT_ULL(28)
> +
> #define TDX_ATTRIBUTES_MAX_BITS 64
>
> static FeatureMask tdx_attrs_ctrl_fields[TDX_ATTRIBUTES_MAX_BITS] = {
> @@ -501,6 +503,24 @@ out:
> return r;
> }
>
> +static bool tdx_guest_get_sept_ve_disable(Object *obj, Error **errp)
> +{
> + TdxGuest *tdx = TDX_GUEST(obj);
> +
> + return !!(tdx->attributes & TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE);
> +}
> +
> +static void tdx_guest_set_sept_ve_disable(Object *obj, bool value, Error **errp)
> +{
> + TdxGuest *tdx = TDX_GUEST(obj);
> +
> + if (value) {
> + tdx->attributes |= TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE;
> + } else {
> + tdx->attributes &= ~TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE;
> + }
> +}
> +
> /* tdx guest */
> OBJECT_DEFINE_TYPE_WITH_INTERFACES(TdxGuest,
> tdx_guest,
> @@ -516,6 +536,10 @@ static void tdx_guest_init(Object *obj)
> qemu_mutex_init(&tdx->lock);
>
> tdx->attributes = 0;
> +
> + object_property_add_bool(obj, "sept-ve-disable",
> + tdx_guest_get_sept_ve_disable,
> + tdx_guest_set_sept_ve_disable);
> }
>
> static void tdx_guest_finalize(Object *obj)
> --
> 2.34.1
>
With regards,
Daniel
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