From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 2/4] mm, s390: Ignore MADV_HUGEPAGE on s390 to prevent SIGSEGV in qemu Date: Fri, 28 Feb 2014 12:42:36 +0100 Message-ID: <5310762C.90108@redhat.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: owner-linux-mm@kvack.org To: Alex Thorlton , linux-kernel@vger.kernel.org Cc: Gerald Schaefer , Martin Schwidefsky , Heiko Carstens , Christian Borntraeger , Andrew Morton , "Kirill A. Shutemov" , Mel Gorman , Rik van Riel , Ingo Molnar , Peter Zijlstra , Andrea Arcangeli , Oleg Nesterov , "Eric W. Biederman" , Alexander Viro , linux390@de.ibm.com, linux-s390@vger.kernel.org, linux-mm@kvack.org, linux-api@vger.kernel.org List-Id: linux-api@vger.kernel.org Il 27/02/2014 18:23, Alex Thorlton ha scritto: > As Christian pointed out, the recent 'Revert "thp: make MADV_HUGEPAGE > check for mm->def_flags"' breaks qemu, it does QEMU_MADV_HUGEPAGE for > all kvm pages but this doesn't work after s390_enable_sie/thp_split_mm. > > Paolo suggested that instead of failing on the call to madvise, we > simply ignore the call (return 0). > > Reported-by: Christian Borntraeger > Suggested-by: Paolo Bonzini > Suggested-by: Oleg Nesterov > Signed-off-by: Alex Thorlton > Cc: Gerald Schaefer > Cc: Martin Schwidefsky > Cc: Heiko Carstens > Cc: Christian Borntraeger > Cc: Andrew Morton > Cc: Paolo Bonzini > Cc: "Kirill A. Shutemov" > Cc: Mel Gorman > Cc: Rik van Riel > Cc: Ingo Molnar > Cc: Peter Zijlstra > Cc: Andrea Arcangeli > Cc: Oleg Nesterov > Cc: "Eric W. Biederman" > Cc: Alexander Viro > Cc: linux390@de.ibm.com > Cc: linux-s390@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Cc: linux-mm@kvack.org > Cc: linux-api@vger.kernel.org > > --- > mm/huge_memory.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index a4310a5..61d234d 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -1970,6 +1970,15 @@ int hugepage_madvise(struct vm_area_struct *vma, > { > switch (advice) { > case MADV_HUGEPAGE: > +#ifdef CONFIG_S390 > + /* > + * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390 > + * can't handle this properly after s390_enable_sie, so we simply > + * ignore the madvise to prevent qemu from causing a SIGSEGV. > + */ > + if (mm_has_pgste(vma->vm_mm)) > + return 0; > +#endif > /* > * Be somewhat over-protective like KSM for now! > */ > Acked-by: Paolo Bonzini -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org