From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2BB69C0044C for ; Wed, 31 Oct 2018 17:15:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F13FB2080A for ; Wed, 31 Oct 2018 17:15:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F13FB2080A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729620AbeKACOJ (ORCPT ); Wed, 31 Oct 2018 22:14:09 -0400 Received: from foss.arm.com ([217.140.101.70]:44140 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728128AbeKACOJ (ORCPT ); Wed, 31 Oct 2018 22:14:09 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6628280D; Wed, 31 Oct 2018 10:15:13 -0700 (PDT) Received: from localhost (e105922-lin.cambridge.arm.com [10.1.197.25]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DA3A03F6A8; Wed, 31 Oct 2018 10:15:12 -0700 (PDT) From: Punit Agrawal To: Christoffer Dall Cc: marc.zyngier@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, stable@vger.kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v8 1/9] KVM: arm/arm64: Ensure only THP is candidate for adjustment References: <20181001155443.23032-1-punit.agrawal@arm.com> <20181001155443.23032-2-punit.agrawal@arm.com> <20181031143646.GE12057@e113682-lin.lund.arm.com> <87h8h2rwwr.fsf@e105922-lin.cambridge.arm.com> Date: Wed, 31 Oct 2018 17:15:10 +0000 In-Reply-To: <87h8h2rwwr.fsf@e105922-lin.cambridge.arm.com> (Punit Agrawal's message of "Wed, 31 Oct 2018 14:52:20 +0000") Message-ID: <87d0rqrqap.fsf@e105922-lin.cambridge.arm.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Punit Agrawal writes: > Christoffer Dall writes: > >> On Mon, Oct 01, 2018 at 04:54:35PM +0100, Punit Agrawal wrote: >>> PageTransCompoundMap() returns true for hugetlbfs and THP >>> hugepages. This behaviour incorrectly leads to stage 2 faults for >>> unsupported hugepage sizes (e.g., 64K hugepage with 4K pages) to be >>> treated as THP faults. >>> >>> Tighten the check to filter out hugetlbfs pages. This also leads to >>> consistently mapping all unsupported hugepage sizes as PTE level >>> entries at stage 2. >>> >>> Signed-off-by: Punit Agrawal >>> Reviewed-by: Suzuki Poulose >>> Cc: Christoffer Dall >>> Cc: Marc Zyngier >>> Cc: stable@vger.kernel.org # v4.13+ >> >> >> Hmm, this function is only actually called from user_mem_abort() if we >> have (!hugetlb), so I'm not sure the cc stable here was actually >> warranted, nor that this patch is strictly necessary. >> >> It doesn't hurt, and makes the code potentially more robust for the >> future though. >> >> Am I missing something? > > !hugetlb is only true for hugepage sizes supported at stage 2. Of course I meant "hugetlb" above (Note the lack of "!"). > The function also got called for unsupported hugepage size at stage 2, > e.g., 64k hugepage with 4k page size, which then ended up doing the > wrong thing. > > Hope that adds some context. I should've added this to the commit log. > >> >> Thanks, >> >> Christoffer >> >>> --- >>> virt/kvm/arm/mmu.c | 8 +++++++- >>> 1 file changed, 7 insertions(+), 1 deletion(-) >>> >>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c >>> index 7e477b3cae5b..c23a1b323aad 100644 >>> --- a/virt/kvm/arm/mmu.c >>> +++ b/virt/kvm/arm/mmu.c >>> @@ -1231,8 +1231,14 @@ static bool transparent_hugepage_adjust(kvm_pfn_t *pfnp, phys_addr_t *ipap) >>> { >>> kvm_pfn_t pfn = *pfnp; >>> gfn_t gfn = *ipap >> PAGE_SHIFT; >>> + struct page *page = pfn_to_page(pfn); >>> >>> - if (PageTransCompoundMap(pfn_to_page(pfn))) { >>> + /* >>> + * PageTransCompoungMap() returns true for THP and >>> + * hugetlbfs. Make sure the adjustment is done only for THP >>> + * pages. >>> + */ >>> + if (!PageHuge(page) && PageTransCompoundMap(page)) { >>> unsigned long mask; >>> /* >>> * The address we faulted on is backed by a transparent huge >>> -- >>> 2.18.0 >>> > _______________________________________________ > kvmarm mailing list > kvmarm@lists.cs.columbia.edu > https://lists.cs.columbia.edu/mailman/listinfo/kvmarm