linux-kernel - Re: [PATCH] hugetlbfs: add MTE support

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Date: Wed, 26 Jun 2024 16:43:02 -0700
From: Yang Shi <shy828301@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Yang Shi <yang@...amperecomputing.com>, muchun.song@...ux.dev, 
	catalin.marinas@....com, will@...nel.org, linux-mm@...ck.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hugetlbfs: add MTE support

On Wed, Jun 26, 2024 at 1:45 PM Yang Shi <shy828301@...il.com> wrote:
>
> On Wed, Jun 26, 2024 at 1:40 PM Andrew Morton <akpm@...ux-foundation.org> wrote:
> >
> > On Tue, 25 Jun 2024 16:37:17 -0700 Yang Shi <yang@...amperecomputing.com> wrote:
> >
> > > MTE can be supported on ram based filesystem. It is supported on tmpfs.
> > > There is use case to use MTE on hugetlbfs as well, adding MTE support.
> > >
> > > --- a/fs/hugetlbfs/inode.c
> > > +++ b/fs/hugetlbfs/inode.c
> > > @@ -110,7 +110,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma)
> > >        * way when do_mmap unwinds (may be important on powerpc
> > >        * and ia64).
> > >        */
> > > -     vm_flags_set(vma, VM_HUGETLB | VM_DONTEXPAND);
> > > +     vm_flags_set(vma, VM_HUGETLB | VM_DONTEXPAND | VM_MTE_ALLOWED);
> > >       vma->vm_ops = &hugetlb_vm_ops;
> > >
> > >       ret = seal_check_write(info->seals, vma);
> >
> > How thoroughly has this been tested?
> >
> > Can we expect normal linux-next testing to exercise this, or must
> > testers make special arangements to get the coverage?
>
> It requires special arrangements. This needs hardware support and
> custom-patched QEMU. We did in-house test on AmpereOne platform with
> patched QEMU 8.1.

To correct, custom-patched QEMU is not required for a minimum test.
But a special test program is definitely needed. We used
custom-patched QEMU to test VM backed by hugetlbfs with MTE enabled.

>
> >