linux-kernel - Re: [PATCH 4/4] asm-generic/hyperv: Add definitions for Get/SetVpRegister hypercalls

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Message-ID: <87y2qpq9e7.fsf@vitty.brq.redhat.com>
Date:   Tue, 21 Apr 2020 15:02:40 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Michael Kelley <mikelley@...rosoft.com>
Cc:     mikelley@...rosoft.com, kys@...rosoft.com, haiyangz@...rosoft.com,
        sthemmin@...rosoft.com, wei.liu@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        pbonzini@...hat.com, sean.j.christopherson@...el.com,
        wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-hyperv@...r.kernel.org
Subject: Re: [PATCH 4/4] asm-generic/hyperv: Add definitions for Get/SetVpRegister hypercalls

Michael Kelley <mikelley@...rosoft.com> writes:

> Add definitions for GetVpRegister and SetVpRegister hypercalls, which
> are implemented for both x86 and ARM64.
>
> Signed-off-by: Michael Kelley <mikelley@...rosoft.com>
> ---
>  include/asm-generic/hyperv-tlfs.h | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
>
> diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
> index 1f92ef92eb56..29b60f5b6323 100644
> --- a/include/asm-generic/hyperv-tlfs.h
> +++ b/include/asm-generic/hyperv-tlfs.h
> @@ -141,6 +141,8 @@ struct ms_hyperv_tsc_page {
>  #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX	0x0013
>  #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX	0x0014
>  #define HVCALL_SEND_IPI_EX			0x0015
> +#define HVCALL_GET_VP_REGISTERS			0x0050
> +#define HVCALL_SET_VP_REGISTERS			0x0051
>  #define HVCALL_POST_MESSAGE			0x005c
>  #define HVCALL_SIGNAL_EVENT			0x005d
>  #define HVCALL_RETARGET_INTERRUPT		0x007e
> @@ -439,4 +441,30 @@ struct hv_retarget_device_interrupt {
>  	struct hv_device_interrupt_target int_target;
>  } __packed __aligned(8);
>  
> +
> +/* HvGetVPRegister hypercall */

Nit: 'HvGetVpRegisters' in TLFS

> +struct hv_get_vp_register_input {

Nit: I would also to name it 'hv_get_vp_registers_input' (plural, like
the hypercall).

> +	u64 partitionid;
> +	u32 vpindex;
> +	u8  inputvtl;
> +	u8  padding[3];
> +	u32 name0;
> +	u32 name1;
> +} __packed;

Isn't it a REP hypercall where we can we can pass a list? In that case
this should look like

struct hv_get_vp_registers_input {
	struct {
		u64 partitionid;
		u32 vpindex;
		u8  inputvtl;
		u8  padding[3];
        } header;
	struct {
		u32 name0;
		u32 name1;
        } elem[];
} __packed;

> +
> +struct hv_get_vp_register_output {

Ditto.

> +	union {
> +		struct {
> +			u32 a;
> +			u32 b;
 > +			u32 c;
> +			u32 d;
> +		} as32 __packed;
> +		struct {
> +			u64 low;
> +			u64 high;
> +		} as64 __packed;
> +	};
> +};

I'm wondering why you define both
HVCALL_GET_VP_REGISTERS/HVCALL_SET_VP_REGISTERS but only add 'struct
hv_get_vp_register_input' and not 'struct hv_set_vp_register_input'. 

The later should look similar, AFAIU it is:

struct hv_set_vp_registers_input {
	struct {
		u64 partitionid;
		u32 vpindex;
		u8  inputvtl;
		u8  padding[3];
        } header;
	struct {
		u32 name;
		u32 padding1;
		u64 padding2; //not sure this is not a mistake in TLFS
            	u64 regvallow;
            	u64 regvalhigh;
	} elem[];
} __packed;

> +
>  #endif

-- 
Vitaly