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

David Hildenbrand
2025-02-26T17:01:10Z

On 26.02.25 17:58, Claudio Imbrenda wrote:
> On Wed, 26 Feb 2025 16:05:11 +0100
> David Hildenbrand <david@redhat.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

Can you elaborate why it is not needed? Would the HW enforce that
writability check already?

--
Cheers,

David / dhildenb