linux-kernel - Re: [PATCH v2] mshv: Extend create partition ioctl to support cpu features

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Message-ID: <20251107181457.GC4041739@liuwe-devbox-debian-v2.local>
Date: Fri, 7 Nov 2025 18:14:57 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Cc: Wei Liu <wei.liu@...nel.org>, linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org, muislam@...rosoft.com,
	kys@...rosoft.com, haiyangz@...rosoft.com, decui@...rosoft.com,
	longli@...rosoft.com, mhklinux@...look.com,
	skinsburskii@...ux.microsoft.com, romank@...ux.microsoft.com,
	Jinank Jain <jinankjain@...rosoft.com>
Subject: Re: [PATCH v2] mshv: Extend create partition ioctl to support cpu
 features

On Fri, Oct 31, 2025 at 01:08:45PM -0700, Nuno Das Neves wrote:
> On 10/31/2025 11:31 AM, Wei Liu wrote:
> > On Thu, Oct 30, 2025 at 02:40:31PM -0700, Nuno Das Neves wrote:
> >> From: Muminul Islam <muislam@...rosoft.com>
> >>
> >> The existing mshv create partition ioctl does not provide a way to
> >> specify which cpu features are enabled in the guest. This was done
> >> to reduce unnecessary complexity in the API.
> >>
> >> However, some new scenarios require fine-grained control over the
> >> cpu feature bits.
> >>
> >> Define a new mshv_create_partition_v2 structure which supports passing
> >> through the disabled cpu flags and xsave flags to the hypervisor
> >> directly.
> >>
> >> When these are not specified (pt_num_cpu_fbanks == 0) or the old
> >> structure is used, define a set of default flags which cover most
> >> cases.
> >>
> >> Retain backward compatibility with the old structure via a new flag
> >> MSHV_PT_BIT_CPU_AND_XSAVE_FEATURES which enables the new struct.
> >>
> >> Co-developed-by: Jinank Jain <jinankjain@...rosoft.com>
> >> Signed-off-by: Jinank Jain <jinankjain@...rosoft.com>
> >> Signed-off-by: Muminul Islam <muislam@...rosoft.com>
> >> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
> >> ---
> >> Changes in v2:
> >> - Fix compilation issues [kernel test robot]
> >>
> >> ---
> >>  drivers/hv/mshv_root_main.c | 176 ++++++++++++++++++++++++++++++++----
> >>  include/hyperv/hvhdk.h      |  86 +++++++++++++++++-
> > 
> > There is no mention of updating hvhdk.h in the commit message.
> > 
> Ah, that's true..
> 
> > Can you split out this part to a separate commit?
> 
> I put the header changes in this patch because a patch containing
> those alone doesn't have much merit on its own.
> 
> I know we have split header changes into separate patches in the
> past but I'm not sure it's always the right choice.
> 

This makes it easier for me or other maintainers to track specifically
the header changes.

> Thinking about this, I could also split it up another way: one
> patch to introduce the new cpu features flags and use them in the
> driver, and one patch to introduce mshv_create_partition_v2.

That's fine by me.

Wei

> 
> Nuno> 
> > Wei
>