linux-kernel - Re: [PATCH] s390/kvm: avoid hypfs error message

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Message-ID: <YrA7lHb38Sj74+4U@osiris>
Date:   Mon, 20 Jun 2022 11:19:16 +0200
From:   Heiko Carstens <hca@...ux.ibm.com>
To:     Christian Borntraeger <borntraeger@...ux.ibm.com>
Cc:     Juergen Gross <jgross@...e.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Sven Schnelle <svens@...ux.ibm.com>
Subject: Re: [PATCH] s390/kvm: avoid hypfs error message

On Mon, Jun 20, 2022 at 09:18:37AM +0200, Christian Borntraeger wrote:
> Am 20.06.22 um 08:03 schrieb Juergen Gross:
> > Ping?
> > 
> > On 07.06.22 14:33, Juergen Gross wrote:
> > > When booting under KVM the following error messages are issued:
> > > 
> > > hypfs.7f5705: The hardware system does not support hypfs
> > > hypfs.7a79f0: Initialization of hypfs failed with rc=-61
> > > 
> > > While being documented, they can easily be avoided by bailing out of
> > > hypfs_init() early in case of running as a KVM guest.
> > > 
> > > Signed-off-by: Juergen Gross <jgross@...e.com>
> > > ---
> > >   arch/s390/hypfs/inode.c | 3 +++
> > >   1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/arch/s390/hypfs/inode.c b/arch/s390/hypfs/inode.c
> > > index 5c97f48cea91..bdf078f3c641 100644
> > > --- a/arch/s390/hypfs/inode.c
> > > +++ b/arch/s390/hypfs/inode.c
> > > @@ -464,6 +464,9 @@ static int __init hypfs_init(void)
> > >   {
> > >       int rc;
> > > +    if (MACHINE_IS_KVM)
> > > +        return -ENODATA;
> > > +
> > >       hypfs_dbfs_init();
> > >       if (hypfs_diag_init()) {
> 
> In case KVM implements hypfs this check would then be wrong.
> Question to people on CC/TO.
> Would it be an option to still check with KVM but avoid the error message.
> So basically changing hypfs_diag_init and fail_dbfs_exit to check
> for KVM on error?
> Or is this worse?

I'd say just move the pr_err("Initialization of hypfs failed with...")
one label above to fail_hypfs_diag_exit. Then we still get the message
that the hardware system doesn't support hypfs, which seems to be
wanted, and the error message only appears for an error.

Even though I personally dislike printing everything to the console
this seems to be what is/was preferred. So let's keep that.