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

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Message-ID: <0dfeabca-5c41-4555-a43b-341a54096036@redhat.com>
Date: Wed, 26 Feb 2025 16:05:11 +0100
From: David Hildenbrand <david@...hat.com>
To: Claudio Imbrenda <imbrenda@...ux.ibm.com>, kvm@...r.kernel.org
Cc: 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

> +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.

-- 
Cheers,

David / dhildenb