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

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Message-ID: <MW2PR2101MB1052EF4972CDCF9BF2B0356AD7D50@MW2PR2101MB1052.namprd21.prod.outlook.com>
Date:   Tue, 21 Apr 2020 15:50:12 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     vkuznets <vkuznets@...hat.com>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>,
        "hpa@...or.com" <hpa@...or.com>,
        "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "sean.j.christopherson@...el.com" <sean.j.christopherson@...el.com>,
        "wanpengli@...cent.com" <wanpengli@...cent.com>,
        "jmattson@...gle.com" <jmattson@...gle.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>
Subject: RE: [PATCH 4/4] asm-generic/hyperv: Add definitions for
 Get/SetVpRegister hypercalls

From: Vitaly Kuznetsov <vkuznets@...hat.com> Sent: Tuesday, April 21, 2020 6:03 AM
> 
> 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

Thanks.  I'll make these changes.  I was being a bit lazy since
the ARM64 code only gets/sets a single register at a time.  Also
HvSetVpRegisters works very nicely as a fast hypercall when setting
a single register, so I didn't define the in-memory data structure.
But for completeness, I shouldn't take these shortcuts, so I'll do
an update.

Michael