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To:     Jinank Jain <jinankjain@linux.microsoft.com>,
        Jinank Jain <jinankjain@microsoft.com>
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Subject: RE: [PATCH v10 3/5] x86/hyperv: Add an interface to do nested
 hypercalls
Thread-Topic: [PATCH v10 3/5] x86/hyperv: Add an interface to do nested
 hypercalls
Thread-Index: AQHZHnmpvVLD+m3uzEu9T0k4Q2fsXa6Ktk+AgAJbIQA=
Date:   Tue, 3 Jan 2023 19:12:07 +0000
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 <24f9d46d5259a688113e6e5e69e21002647f4949.1672639707.git.jinankjain@linux.microsoft.com>
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From: Jinank Jain <jinankjain@linux.microsoft.com> Sent: Sunday, January 1,=
 2023 11:13 PM
>=20
> According to TLFS, in order to communicate to L0 hypervisor there needs
> to be an additional bit set in the control register. This communication
> is required to perform privileged instructions which can only be
> performed by L0 hypervisor. An example of that could be setting up the
> VMBus infrastructure.
>=20
> Signed-off-by: Jinank Jain <jinankjain@linux.microsoft.com>
> ---
>  arch/x86/include/asm/hyperv-tlfs.h |  3 ++-
>  arch/x86/include/asm/mshyperv.h    | 42 +++++++++++++++++++++++++++---
>  include/asm-generic/hyperv-tlfs.h  |  1 +
>  3 files changed, 41 insertions(+), 5 deletions(-)
>=20
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hy=
perv-tlfs.h
> index b5019becb618..7758c495541d 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -380,7 +380,8 @@ struct hv_nested_enlightenments_control {
>  		__u32 reserved:31;
>  	} features;
>  	struct {
> -		__u32 reserved;
> +		__u32 inter_partition_comm:1;
> +		__u32 reserved:31;
>  	} hypercallControls;
>  } __packed;
>=20
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyp=
erv.h
> index c38e4c66a3ac..9e5535044ed0 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -74,10 +74,16 @@ static inline u64 hv_do_hypercall(u64 control, void *=
input, void
> *output)
>  	return hv_status;
>  }
>=20
> +/* Hypercall to the L0 hypervisor */
> +static inline u64 hv_do_nested_hypercall(u64 control, void *input, void =
*output)
> +{
> +	return hv_do_hypercall(control | HV_HYPERCALL_NESTED, input, output);
> +}
> +
>  /* Fast hypercall with 8 bytes of input and no output */
> -static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
> +static inline u64 _hv_do_fast_hypercall8(u64 control, u64 input1)
>  {
> -	u64 hv_status, control =3D (u64)code | HV_HYPERCALL_FAST_BIT;
> +	u64 hv_status;
>=20
>  #ifdef CONFIG_X86_64
>  	{
> @@ -105,10 +111,24 @@ static inline u64 hv_do_fast_hypercall8(u16 code, u=
64
> input1)
>  		return hv_status;
>  }
>=20
> +static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
> +{
> +	u64 control =3D (u64)code | HV_HYPERCALL_FAST_BIT;
> +
> +	return _hv_do_fast_hypercall8(control, input1);
> +}
> +
> +static inline u64 hv_do_fast_nested_hypercall8(u16 code, u64 input1)
> +{
> +	u64 control =3D (u64)code | HV_HYPERCALL_FAST_BIT | HV_HYPERCALL_NESTED=
;
> +
> +	return _hv_do_fast_hypercall8(control, input1);
> +}
> +
>  /* Fast hypercall with 16 bytes of input */
> -static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input=
2)
> +static inline u64 _hv_do_fast_hypercall16(u64 control, u64 input1, u64 i=
nput2)
>  {
> -	u64 hv_status, control =3D (u64)code | HV_HYPERCALL_FAST_BIT;
> +	u64 hv_status;
>=20
>  #ifdef CONFIG_X86_64
>  	{
> @@ -139,6 +159,20 @@ static inline u64 hv_do_fast_hypercall16(u16 code, u=
64
> input1, u64 input2)
>  	return hv_status;
>  }
>=20
> +static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input=
2)
> +{
> +	u64 control =3D (u64)code | HV_HYPERCALL_FAST_BIT;
> +
> +	return _hv_do_fast_hypercall16(control, input1, input2);
> +}
> +
> +static inline u64 hv_do_fast_nested_hypercall16(u16 code, u64 input1, u6=
4 input2)
> +{
> +	u64 control =3D (u64)code | HV_HYPERCALL_FAST_BIT | HV_HYPERCALL_NESTED=
;
> +
> +	return _hv_do_fast_hypercall16(control, input1, input2);
> +}
> +
>  extern struct hv_vp_assist_page **hv_vp_assist_page;
>=20
>  static inline struct hv_vp_assist_page *hv_get_vp_assist_page(unsigned i=
nt cpu)
> diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hype=
rv-tlfs.h
> index b17c6eeb9afa..e61ee461c4fc 100644
> --- a/include/asm-generic/hyperv-tlfs.h
> +++ b/include/asm-generic/hyperv-tlfs.h
> @@ -194,6 +194,7 @@ enum HV_GENERIC_SET_FORMAT {
>  #define HV_HYPERCALL_VARHEAD_OFFSET	17
>  #define HV_HYPERCALL_VARHEAD_MASK	GENMASK_ULL(26, 17)
>  #define HV_HYPERCALL_RSVD0_MASK		GENMASK_ULL(31, 27)
> +#define HV_HYPERCALL_NESTED		BIT_ULL(31)
>  #define HV_HYPERCALL_REP_COMP_OFFSET	32
>  #define HV_HYPERCALL_REP_COMP_1		BIT_ULL(32)
>  #define HV_HYPERCALL_REP_COMP_MASK	GENMASK_ULL(43, 32)
> --
> 2.25.1

Reviewed-by: Michael Kelley <mikelley@microsoft.com>