RE: [PATCH v10 3/5] x86/hyperv: Add an interface to do nested hypercalls

Michael Kelley (LINUX)
2023-01-03T19:12:52Z

From: Jinank Jain <jinankjain@linux.microsoft.com> Sent: Sunday, January 1, 2023 11:13 PM
>
> 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.
>
> 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(-)
>
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-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;
>
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.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;
> }
>
> +/* 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 = (u64)code | HV_HYPERCALL_FAST_BIT;
> + u64 hv_status;
>
> #ifdef CONFIG_X86_64
> {
> @@ -105,10 +111,24 @@ static inline u64 hv_do_fast_hypercall8(u16 code, u64
> input1)
> return hv_status;
> }
>
> +static inline u64 hv_do_fast_hypercall8(u16 code, u64 input1)
> +{
> + u64 control = (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 = (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 input2)
> +static inline u64 _hv_do_fast_hypercall16(u64 control, u64 input1, u64 input2)
> {
> - u64 hv_status, control = (u64)code | HV_HYPERCALL_FAST_BIT;
> + u64 hv_status;
>
> #ifdef CONFIG_X86_64
> {
> @@ -139,6 +159,20 @@ static inline u64 hv_do_fast_hypercall16(u16 code, u64
> input1, u64 input2)
> return hv_status;
> }
>
> +static inline u64 hv_do_fast_hypercall16(u16 code, u64 input1, u64 input2)
> +{
> + u64 control = (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, u64 input2)
> +{
> + u64 control = (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;
>
> static inline struct hv_vp_assist_page *hv_get_vp_assist_page(unsigned int cpu)
> diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-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>