linux-kernel - RE: [PATCH] Drivers: hv: Introduce mshv

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Message-ID:
 <KUZP153MB14448028621F8148D5129D9FBE8BA@KUZP153MB1444.APCP153.PROD.OUTLOOK.COM>
Date: Thu, 8 May 2025 03:00:33 +0000
From: Saurabh Singh Sengar <ssengar@...rosoft.com>
To: Roman Kisel <romank@...ux.microsoft.com>, Naman Jain
	<namjain@...ux.microsoft.com>, KY Srinivasan <kys@...rosoft.com>, Haiyang
 Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>, Dexuan Cui
	<decui@...rosoft.com>
CC: Anirudh Rayabharam <anrayabh@...ux.microsoft.com>, Saurabh Sengar
	<ssengar@...ux.microsoft.com>, Stanislav Kinsburskii
	<skinsburskii@...ux.microsoft.com>, Nuno Das Neves
	<nunodasneves@...ux.microsoft.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-hyperv@...r.kernel.org"
	<linux-hyperv@...r.kernel.org>
Subject: RE: [PATCH] Drivers: hv: Introduce mshv_vtl driver

> 
> On 5/7/2025 4:21 AM, Naman Jain wrote:
> >
> >
> 
> [...]
> 
> > <snip>
> >
> >>> +        return -EINVAL;
> >>> +    if (copy_from_user(payload, (void __user *)message.payload_ptr,
> >>> +               message.payload_size))
> >>> +        return -EFAULT;
> >>> +
> >>> +    return hv_post_message((union
> >>
> >> This function definition is in separate file which can be build as
> >> independent module, this will cause problem while linking . Try
> >> building with CONFIG_HYPERV=m and check.
> >>
> >> - Saurabh
> >
> > Thanks for reviewing Saurabh. As CONFIG_HYPERV can be set to 'm'
> > and CONFIG_MSHV_VTL depends on it, changing CONFIG_MSHV_VTL to
> > tristate and a few tweaks in Makefile will fix this issue. This will
> > ensure that mshv_vtl is also built as a module when hyperv is built as a
> module.
> >
> > I'll take care of this in next version.
> 
> Let me ask for a clarification. How would the system boot if CONFIG_HYPERV
> is set to m? The arch parts are going to be still compiled-in, correct?
> Otherwise I don't see how that would initialize.
> 
> I am thinking who would load Hyper-V modules on the system that requires
> Hyper-V here. It is understandable that distro's build Hyper-V as a module.
> That way, they don't have to load anything when there is no Hyper-V. Here, it
> is Hyper-V in and out, what do we need to fix?

We need to fix compilation - for everyone.

- Saurabh

> 
> >
> > here is the diff for reference:
> > diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig index
> > 57dcfcb69b88..c7f21b483377 100644
> > --- a/drivers/hv/Kconfig
> > +++ b/drivers/hv/Kconfig
> > @@ -73,7 +73,7 @@ config MSHV_ROOT
> >            If unsure, say N.
> >
> >   config MSHV_VTL
> > -       bool "Microsoft Hyper-V VTL driver"
> > +       tristate "Microsoft Hyper-V VTL driver"
> >          depends on HYPERV && X86_64
> >          depends on TRANSPARENT_HUGEPAGE
> >          depends on OF
> > diff --git a/drivers/hv/Makefile b/drivers/hv/Makefile index
> > 5e785dae08cc..c53a0df746b7 100644
> > --- a/drivers/hv/Makefile
> > +++ b/drivers/hv/Makefile
> > @@ -15,9 +15,11 @@ hv_vmbus-$(CONFIG_HYPERV_TESTING)    +=
> > hv_debugfs.o
> >   hv_utils-y := hv_util.o hv_kvp.o hv_snapshot.o hv_utils_transport.o
> >   mshv_root-y := mshv_root_main.o mshv_synic.o mshv_eventfd.o
> > mshv_irq.o \
> >                 mshv_root_hv_call.o mshv_portid_table.o
> > +mshv_vtl-y := mshv_vtl_main.o
> >
> >   # Code that must be built-in
> >   obj-$(subst m,y,$(CONFIG_HYPERV)) += hv_common.o -obj-$(subst
> > m,y,$(CONFIG_MSHV_ROOT)) += hv_proc.o mshv_common.o
> > -
> > -mshv_vtl-y := mshv_vtl_main.o mshv_common.o
> > +obj-$(subst m,y,$(CONFIG_MSHV_ROOT)) += hv_proc.o ifneq
> > +($(CONFIG_MSHV_ROOT) $(CONFIG_MSHV_VTL),)
> > +    obj-y += mshv_common.o
> > +endif
> >
> > Regards,
> > Naman
> 
> --
> Thank you,
> Roman