linux-kernel - Re: [PATCH v7 4/7] Drivers: hv: Fix huge page handling in memory region traversal

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Message-ID: <aS3d7Ybs2iS4qo13@skinsburskii.localdomain>
Date: Mon, 1 Dec 2025 10:26:53 -0800
From: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
To: Anirudh Rayabharam <anirudh@...rudhrb.com>
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
	decui@...rosoft.com, linux-hyperv@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 4/7] Drivers: hv: Fix huge page handling in memory
 region traversal

On Mon, Dec 01, 2025 at 03:09:41PM +0000, Anirudh Rayabharam wrote:
> On Wed, Nov 26, 2025 at 02:09:11AM +0000, Stanislav Kinsburskii wrote:
> > The previous code assumed that if a region's first page was huge, the
> > entire region consisted of huge pages and stored this in a large_pages
> > flag. This premise is incorrect not only for movable regions (where
> > pages can be split and merged on invalidate callbacks or page faults),
> > but even for pinned regions: THPs can be split and merged during
> > allocation, so a large, pinned region may contain a mix of huge and
> > regular pages.
> > 
> > This change removes the large_pages flag and replaces region-wide
> > assumptions with per-chunk inspection of the actual page size when
> > mapping, unmapping, sharing, and unsharing. This makes huge page
> > handling correct for mixed-page regions and avoids relying on stale
> > metadata that can easily become invalid as memory is remapped.
> > 
> > Signed-off-by: Stanislav Kinsburskii <skinsburskii@...ux.microsoft.com>
> > ---
> >  drivers/hv/mshv_regions.c |  213 +++++++++++++++++++++++++++++++++++++++------
> >  drivers/hv/mshv_root.h    |    3 -
> >  2 files changed, 184 insertions(+), 32 deletions(-)
> 
> Except the warning reported by kernel test robot:
> 

This one is a good catch.
I'll fix it in the next revision.

Thanks,
Stanislav

> Reviewed-by: Anirudh Rayabharam (Microsoft) <anirudh@...rudhrb.com>