From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Hildenbrand Subject: Re: [RFC/PATCH v2 05/22] s390/mm: hugetlb pages within a gmap can not be freed Date: Wed, 24 Jan 2018 14:45:04 +0100 Message-ID: <07d8227f-ec52-f282-6ecf-d0880f3b74d8@redhat.com> References: <1513169613-13509-1-git-send-email-frankja@linux.vnet.ibm.com> <1513169613-13509-6-git-send-email-frankja@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1513169613-13509-6-git-send-email-frankja@linux.vnet.ibm.com> Content-Language: en-US Sender: kvm-owner@vger.kernel.org List-Archive: List-Post: To: Janosch Frank , kvm@vger.kernel.org Cc: schwidefsky@de.ibm.com, borntraeger@de.ibm.com, dominik.dingel@gmail.com, linux-s390@vger.kernel.org List-ID: On 13.12.2017 13:53, Janosch Frank wrote: > From: Dominik Dingel > > Guests backed by huge pages could theoretically free unused pages via > the diagnose 10 instruction. We currently don't allow that, so we > don't have to refault it once it's needed again. > > Signed-off-by: Dominik Dingel > Reviewed-by: Martin Schwidefsky > --- > arch/s390/mm/gmap.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c > index aceaeb5..056acfc 100644 > --- a/arch/s390/mm/gmap.c > +++ b/arch/s390/mm/gmap.c > @@ -695,6 +695,9 @@ void gmap_discard(struct gmap *gmap, unsigned long from, unsigned long to) > vmaddr |= gaddr & ~PMD_MASK; > /* Find vma in the parent mm */ > vma = find_vma(gmap->mm, vmaddr); > + /* We do not discard pages that are backed by hugetlbfs */ > + if (vma && is_vm_hugetlb_page(vma)) > + continue; > size = min(to - gaddr, PMD_SIZE - (gaddr & ~PMD_MASK)); > zap_page_range(vma, vmaddr, size); > } > This check does not care about split huge pages, correct? (because we're checking the VMA?) -- Thanks, David / dhildenb