Received: by 2002:ac0:98c7:0:0:0:0:0 with SMTP id g7-v6csp6350098imd; Wed, 31 Oct 2018 10:19:27 -0700 (PDT) X-Google-Smtp-Source: AJdET5dLIb8ssStwakNy8aN2ZsqSQLs39Ltj5PFn1Vh8OP5ZAOGdA6gHkXYNwcoJ//qPqFFoqw/3 X-Received: by 2002:a62:6ac4:: with SMTP id f187-v6mr4320079pfc.103.1541006367119; Wed, 31 Oct 2018 10:19:27 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1541006367; cv=none; d=google.com; s=arc-20160816; b=Y5YNvkq4J4/TdoiVw0YmPaMGOAYSdg0ZS3/v0xZn/imFgmmG2XoKAKIZoJ2RkWYLSE fTqQoH6Z3nxDvKjkB7XsGa7Jfmt8v+xwh6TEaPIsj3QneUb9xVVbpjj0dgL9BblPZRxg +AIsWsecczqL0QDseSMYopo5O35DQohMF9gKlVsL+iGHjSX6nsZz1sKAUfxcaJjkWOvl x7FriSF7ujylqzBDdtC3fzWQLWZKnaEflWDbBY8KzRA0PglTKulpE6ITRyY8czT93XtV mlW+arThgmoJnA/VABRLwwl4uU2+/4ujJ3u0RYLIFBuSYvfCJNXM6DqQUGSp7Kc2Odjh BMwA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:mime-version:user-agent:message-id :in-reply-to:date:references:subject:cc:to:from; bh=BervPIKl2YE4++gM9tuwy0PBt1u5hIGs3khxsC9WvYI=; b=FCtQzU0WYU0hE6udc3pxFq1nzb4yg3YiWcRwMx7uRJq+Q1yA0FHxF8FuAjoLtaQjFp P2pDsWzmzk6xAUVdV0CytJaYhW1zlZX14QB96sboK9+cwRzlbN5Lk+RBE6wG/SH3naop T4GWYWDgLLDZCi1QstDPykVaeb/zcsULPAU6gtwdg3RoCRNI2p8KA7G90I6FWyMC/z2G K54Bxh6schS8I7dmZjVQavbpXINndWSeCxs9GEVSpaKyuekTWb0J5EJtWt9j6ks9BM28 f8Fqwurx2B/VefqxzMcMUiO1rKEm+cc58L1LR3A65HAPXhI075osC37Dsnpk4lBVnQmw 1omQ== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id u15-v6si27539612pga.23.2018.10.31.10.19.11; Wed, 31 Oct 2018 10:19:27 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729406AbeKACOJ (ORCPT + 99 others); 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