linux-kernel - Re: [RFC PATCH 4/6] x86/Hyper-V: Allow Hyper-V to inject Hyper-V vectors

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Message-ID: <CAMvTesA7LbQpqFA=K+romUaphUo23zPNvW-J2P4LmGiBGYZEfA@mail.gmail.com>
Date: Fri, 16 May 2025 23:39:02 +0800
From: Tianyu Lan <ltykernel@...il.com>
To: Michael Kelley <mhklinux@...look.com>
Cc: "kys@...rosoft.com" <kys@...rosoft.com>, "haiyangz@...rosoft.com" <haiyangz@...rosoft.com>, 
	"wei.liu@...nel.org" <wei.liu@...nel.org>, "decui@...rosoft.com" <decui@...rosoft.com>, 
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	"tiala@...rosoft.com" <tiala@...rosoft.com>, 
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 4/6] x86/Hyper-V: Allow Hyper-V to inject Hyper-V vectors

On Thu, May 15, 2025 at 12:54 AM Michael Kelley <mhklinux@...look.com> wrote:
>
> From: Tianyu Lan <ltykernel@...il.com> Sent: Tuesday, May 6, 2025 6:07 AM
> >
>
> Update Subject prefix to "x86/hyperv".
>
> > When Secure AVIC is enabled, call Secure AVIC
> > function to allow Hyper-V to inject REENLIGHTENMENT,
> > STIMER0 and CALLBACK vectors.
> >
> > Signed-off-by: Tianyu Lan <tiala@...rosoft.com>
> > ---
> >  arch/x86/hyperv/hv_init.c | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> > index ddeb40930bc8..d75df5c3965d 100644
> > --- a/arch/x86/hyperv/hv_init.c
> > +++ b/arch/x86/hyperv/hv_init.c
> > @@ -131,6 +131,18 @@ static int hv_cpu_init(unsigned int cpu)
> >               wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
> >       }
> >
> > +     /* Allow Hyper-V vector to be injected from Hypervisor. */
> > +     if (ms_hyperv.features & HV_ACCESS_REENLIGHTENMENT)
> > +             x2apic_savic_update_vector(cpu,
> > +                                        HYPERV_REENLIGHTENMENT_VECTOR, true);
>
> This will allow Hyper-V to submit the re-enlightenment interrupt on
> any vCPU, even though the Linux guest has programmed the interrupt
> to only arrive to a particular vCPU.  That selected vCPU is set up in
> set_hv_tscchange_cb(), and maintained in clear_hv_tscchange_cb()
> and in hv_cpu_die(). I'm not super familiar with the re-enlightenment
> code, but I don't see a problem if Hyper-V sends the interrupt on an
> unexpected vCPU.  So it's probably OK to enable this interrupt vector
> on all vCPUs.
>
Yes, I will double check it. Thanks for suggestion..
--
Thanks
Tianyu Lan