linux-kernel - Re: [PATCH] KVM: s390: Fix to clear PTE when discarding a swapped page

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Message-ID: <20250924143101.5c6e5f4b@p-imbrenda>
Date: Wed, 24 Sep 2025 14:31:01 +0200
From: Claudio Imbrenda <imbrenda@...ux.ibm.com>
To: David Hildenbrand <david@...hat.com>
Cc: Gautam Gala <ggala@...ux.ibm.com>,
        Alexander Gordeev
 <agordeev@...ux.ibm.com>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>, Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Sven Schnelle
 <svens@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH] KVM: s390: Fix to clear PTE when discarding a swapped
 page

On Wed, 24 Sep 2025 14:22:05 +0200
David Hildenbrand <david@...hat.com> wrote:

> On 24.09.25 14:17, Gautam Gala wrote:
> > KVM run fails when guests with 'cmm' cpu feature and host are
> > under memory pressure and use swap heavily. This is because
> > npages becomes ENOMEN (out of memory) in hva_to_pfn_slow()
> > which inturn propagates as EFAULT to qemu. Clearing the page
> > table entry when discarding an address that maps to a swap
> > entry resolves the issue.
> > 
> > Suggested-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>
> > Signed-off-by: Gautam Gala <ggala@...ux.ibm.com>
> > ---  
> 
> Sounds bad,
> 
> I assume we want Fixes: and CC: stable, right?

yes; I'll add those when picking up

Reviewed-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>