linux-kernel - RE: [PATCH v2 2/2] x86/hyperv: VTL support for Hyper-V

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Message-ID: <BYAPR21MB1688264502B9A863E6F9E570D7B99@BYAPR21MB1688.namprd21.prod.outlook.com>
Date:   Mon, 13 Mar 2023 17:25:39 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Saurabh Singh Sengar <ssengar@...ux.microsoft.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
CC:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "arnd@...db.de" <arnd@...db.de>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>
Subject: RE: [PATCH v2 2/2] x86/hyperv: VTL support for Hyper-V

From: Saurabh Singh Sengar <ssengar@...ux.microsoft.com> Sent: Monday, March 13, 2023 10:02 AM
> 
> On Mon, Mar 13, 2023 at 03:45:02PM +0100, Vitaly Kuznetsov wrote:
> > Saurabh Sengar <ssengar@...ux.microsoft.com> writes:
> >

[snip]

> > > diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> > > index 4c4c0ec3b62e..4ff549dcd49a 100644
> > > --- a/arch/x86/include/asm/mshyperv.h
> > > +++ b/arch/x86/include/asm/mshyperv.h
> > > @@ -11,6 +11,10 @@
> > >  #include <asm/paravirt.h>
> > >  #include <asm/mshyperv.h>
> > >
> > > +#define HV_VTL_NORMAL 0x0
> > > +#define HV_VTL_SECURE 0x1
> > > +#define HV_VTL_MGMT   0x2
> >
> > Don't these belong to hyperv-tlfs.h too (even if they're not directly
> > described in Hyper-V TLFS)?
> 
> Can move these to x86/include/asm/hyperv-tlfs.h
> 

While VTL 0 is always the "normal" VTL, the use case for the other
VTLs isn't controlled or specified by Hyper-V.   To me, it did not seem
appropriate to put the definitions of "VTL_SECURE" and "VTL_MGMT
 in the TLFS include file.  My earlier recommendation had been the
Linux-specific mshyperv.h.

That said, to me it's not a big issue either way.  I have a preference
for mshyperv.h, but could go with either. 

Michael

> >
> > > +
> > >  union hv_ghcb;
> > >
> > >  DECLARE_STATIC_KEY_FALSE(isolation_type_snp);
> > > @@ -181,6 +185,11 @@ static inline struct hv_vp_assist_page
> *hv_get_vp_assist_page(unsigned int cpu)
> > >  	return hv_vp_assist_page[cpu];
> > >  }
> > >
> > > +static inline unsigned char hv_get_nmi_reason(void)
> > > +{
> > > +	return 0;
> > > +}
> > > +
> > >  void __init hyperv_init(void);
> > >  void hyperv_setup_mmu_ops(void);
> > >  void set_hv_tscchange_cb(void (*cb)(void));
> > > @@ -266,6 +275,11 @@ static inline int hv_set_mem_host_visibility(unsigned long
> addr, int numpages,
> > >  }
> > >  #endif /* CONFIG_HYPERV */
> > >
> > > +#ifdef CONFIG_HYPERV_VTL
> > > +void __init hv_vtl_init_platform(void);
> > > +#else
> > > +static inline void __init hv_vtl_init_platform(void) {}
> > > +#endif
> > >
> > >  #include <asm-generic/mshyperv.h>
> > >
> > > diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> > > index f36dc2f796c5..da5d13d29c4e 100644
> > > --- a/arch/x86/kernel/cpu/mshyperv.c
> > > +++ b/arch/x86/kernel/cpu/mshyperv.c
> > > @@ -250,11 +250,6 @@ static uint32_t  __init ms_hyperv_platform(void)
> > >  	return HYPERV_CPUID_VENDOR_AND_MAX_FUNCTIONS;
> > >  }
> > >
> > > -static unsigned char hv_get_nmi_reason(void)
> > > -{
> > > -	return 0;
> > > -}
> > > -
> > >  #ifdef CONFIG_X86_LOCAL_APIC
> > >  /*
> > >   * Prior to WS2016 Debug-VM sends NMIs to all CPUs which makes
> > > @@ -521,6 +516,7 @@ static void __init ms_hyperv_init_platform(void)
> > >
> > >  	/* Register Hyper-V specific clocksource */
> > >  	hv_init_clocksource();
> > > +	hv_vtl_init_platform();
> > >  #endif
> > >  	/*
> > >  	 * TSC should be marked as unstable only after Hyper-V
> > > diff --git a/include/asm-generic/hyperv-tlfs.h b/include/asm-generic/hyperv-tlfs.h
> > > index b870983596b9..87258341fd7c 100644
> > > --- a/include/asm-generic/hyperv-tlfs.h
> > > +++ b/include/asm-generic/hyperv-tlfs.h
> > > @@ -146,6 +146,7 @@ union hv_reference_tsc_msr {
> > >  /* Declare the various hypercall operations. */
> > >  #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE	0x0002
> > >  #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST	0x0003
> > > +#define HVCALL_ENABLE_VP_VTL			0x000f
> > >  #define HVCALL_NOTIFY_LONG_SPIN_WAIT		0x0008
> > >  #define HVCALL_SEND_IPI				0x000b
> > >  #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX	0x0013
> > > @@ -165,6 +166,8 @@ union hv_reference_tsc_msr {
> > >  #define HVCALL_MAP_DEVICE_INTERRUPT		0x007c
> > >  #define HVCALL_UNMAP_DEVICE_INTERRUPT		0x007d
> > >  #define HVCALL_RETARGET_INTERRUPT		0x007e
> > > +#define HVCALL_START_VP				0x0099
> > > +#define HVCALL_GET_VP_ID_FROM_APIC_ID		0x009a
> > >  #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_SPACE 0x00af
> > >  #define HVCALL_FLUSH_GUEST_PHYSICAL_ADDRESS_LIST 0x00b0
> > >  #define HVCALL_MODIFY_SPARSE_GPA_PAGE_HOST_VISIBILITY 0x00db
> > > @@ -218,6 +221,7 @@ enum HV_GENERIC_SET_FORMAT {
> > >  #define HV_STATUS_INVALID_PORT_ID		17
> > >  #define HV_STATUS_INVALID_CONNECTION_ID		18
> > >  #define HV_STATUS_INSUFFICIENT_BUFFERS		19
> > > +#define HV_STATUS_VTL_ALREADY_ENABLED		134
> > >
> > >  /*
> > >   * The Hyper-V TimeRefCount register and the TSC
> >
> > --
> > Vitaly