linux-kernel - Re: [PATCH v2 1/1] KVM: s390: pv: fix race when making a page secure

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Message-ID: <20250226175833.16a7a970@p-imbrenda>
Date: Wed, 26 Feb 2025 17:58:33 +0100
From: Claudio Imbrenda <imbrenda@...ux.ibm.com>
To: David Hildenbrand <david@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-s390@...r.kernel.org, frankja@...ux.ibm.com,
        borntraeger@...ibm.com, nrb@...ux.ibm.com, seiden@...ux.ibm.com,
        nsg@...ux.ibm.com, schlameuss@...ux.ibm.com, hca@...ux.ibm.com
Subject: Re: [PATCH v2 1/1] KVM: s390: pv: fix race when making a page
 secure

On Wed, 26 Feb 2025 16:05:11 +0100
David Hildenbrand <david@...hat.com> wrote:

> > +int make_hva_secure(struct mm_struct *mm, unsigned long hva, struct uv_cb_header *uvcb)
> > +{
> > +	struct folio *folio;
> > +	spinlock_t *ptelock;
> > +	pte_t *ptep;
> > +	int rc;
> > +
> > +	ptep = get_locked_valid_pte(mm, hva, &ptelock);
> > +	if (!ptep)
> > +		return -ENXIO;  
> 
> You very likely need a pte_write() check we had there before, as you 
> might effectively modify page content by clearing the page.

it's not really needed, but it doesn't hurt either, I'll add a check