From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:30278 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2388502AbfIRSXB (ORCPT ); Wed, 18 Sep 2019 14:23:01 -0400 Received: from pps.filterd (m0098417.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x8IIMQOV138955 for ; Wed, 18 Sep 2019 14:22:59 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2v3rmcjbk5-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Wed, 18 Sep 2019 14:22:59 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 18 Sep 2019 19:22:57 +0100 Date: Wed, 18 Sep 2019 20:22:43 +0200 From: Gerald Schaefer Subject: Re: [PATCH V2 2/2] mm/pgtable/debug: Add test validating architecture page table helpers In-Reply-To: <64504101-d9dd-f273-02f9-e9a8b178eecc@c-s.fr> References: <1568268173-31302-1-git-send-email-anshuman.khandual@arm.com> <1568268173-31302-3-git-send-email-anshuman.khandual@arm.com> <502c497a-9bf1-7d2e-95f2-cfebcd9cf1d9@arm.com> <95ed9d92-dd43-4c45-2e52-738aed7f2fb5@c-s.fr> <64504101-d9dd-f273-02f9-e9a8b178eecc@c-s.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-Id: <20190918202243.37e709df@thinkpad> Sender: linux-s390-owner@vger.kernel.org List-ID: To: Christophe Leroy Cc: Anshuman Khandual , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Greg Kroah-Hartman , Thomas Gleixner , Mike Rapoport , Jason Gunthorpe , Dan Williams , Peter Zijlstra , Michal Hocko , Mark Rutland , Mark Brown , Steven Price , Ard Biesheuvel , Masahiro Yamada , Kees Cook , Tetsuo Handa , Matthew Wilcox , Sri Krishna chowdary , Dave Hansen , Russell King - ARM Linux , Michael Ellerman , Paul Mackerras , Martin Schwidefsky , Heiko Carstens , "David S. Miller" , Vineet Gupta , James Hogan , Paul Burton , Ralf Baechle , "Kirill A . Shutemov" , linux-snps-arc@lists.infradead.org, linux-mips@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org On Wed, 18 Sep 2019 18:26:03 +0200 Christophe Leroy wrote: [..] > My suggestion was not to completely drop the #ifdef but to do like you > did in pgd_clear_tests() for instance, ie to add the following test on > top of the function: > > if (mm_pud_folded(mm) || is_defined(__ARCH_HAS_5LEVEL_HACK)) > return; > Ah, very nice, this would also fix the remaining issues for s390. Since we have dynamic page table folding, neither __PAGETABLE_PXX_FOLDED nor __ARCH_HAS_XLEVEL_HACK is defined, but mm_pxx_folded() will work. mm_alloc() returns with a 3-level page table by default on s390, so we will run into issues in p4d_clear/populate_tests(), and also at the end with p4d/pud_free() (double free). So, adding the mm_pud_folded() check to p4d_clear/populate_tests(), and also adding mm_p4d/pud_folded() checks at the end before calling p4d/pud_free(), would make it all work on s390. BTW, regarding p4d/pud_free(), I'm not sure if we should rather check the folding inside our s390 functions, similar to how we do it for p4d/pud_free_tlb(), instead of relying on not being called for folded p4d/pud. So far, I see no problem with this behavior, all callers of p4d/pud_free() should be fine because of our folding check within p4d/pud_present/none(). But that doesn't mean that it is correct not to check for the folding inside p4d/pud_free(). At least, with this test module we do now have a caller of p4d/pud_free() on potentially folded entries, so instead of adding pxx_folded() checks to this test module, we could add them to our p4d/pud_free() functions. Any thoughts on this? Regards, Gerald