linux-kernel - Re: [PATCH] s390/mm: Fix in_atomic() handling in do_secure_storage

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Message-ID: <aEFdoYSKqvqK572c@li-008a6a4c-3549-11b2-a85c-c5cc2836eea2.ibm.com>
Date: Thu, 5 Jun 2025 11:04:33 +0200
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Claudio Imbrenda <imbrenda@...ux.ibm.com>
Cc: Heiko Carstens <hca@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Sven Schnelle <svens@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        kvm@...r.kernel.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] s390/mm: Fix in_atomic() handling in
 do_secure_storage_access()

On Wed, Jun 04, 2025 at 07:40:43PM +0200, Claudio Imbrenda wrote:
> > > > This could trigger WARN_ON_ONCE() in handle_fault_error_nolock():
> > > > 
> > > > 		if (WARN_ON_ONCE(!si_code))
> > > > 			si_code = SEGV_MAPERR;
> > > > 
> > > > Would this warning be justified in this case (aka user_mode(regs) ==
> > > > true)?  
> > > 
> > > I think so, because if we are in usermode, we should never trigger
> > > faulthandler_disabled()  
> > 
> > I think I do not get you. We are in a system call and also in_atomic(),
> > so faulthandler_disabled() is true and handle_fault_error_nolock(regs, 0)
> > is called (above).
> 
> what is the psw in regs?
> is it not the one that was being used when the exception was triggered?

Hmm, right. I assume is_kernel_fault() returns false not because 
user_mode(regs) is true, but because we access the secondary AS.

Still, to me it feels wrong to trigger that warning due to a user
process activity. But anyway:

Acked-by: Alexander Gordeev <agordeev@...ux.ibm.com>