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=-10.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 22847C5517A for ; Sun, 25 Oct 2020 10:48:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D61A122314 for ; Sun, 25 Oct 2020 10:48:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603622915; bh=zEZv+ZNBF+WLM11Idj/nftgE/O9ylhR81K3Yn2chkKs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=CQrT1egCD6hPL08URHPJEAHALt+/I3mBRbMbXDfj4uSzigPCJicBZNf5pOOKlrxyk E6FxoCwwPlexiTAv+8r2F5cqPNMpsPyPWlgYAYyaa/rQXnZm6VI9MQ/H6XvPwRnQve /sNJ1lQw0XKZGPi1TcN+vTQ3G64Ip+1GX2tAkq58= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1415252AbgJYKsb (ORCPT ); Sun, 25 Oct 2020 06:48:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:58674 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1415241AbgJYKsa (ORCPT ); Sun, 25 Oct 2020 06:48:30 -0400 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1D03D222D9; Sun, 25 Oct 2020 10:48:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603622910; bh=zEZv+ZNBF+WLM11Idj/nftgE/O9ylhR81K3Yn2chkKs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Pxv8mT386ya9ViOoESPjvo/evUhJWVNTWQbTb6x3v1OTjDWsDVY/zuzO1vzSteNp8 /ftdUuJmDbhLucMIcPJddvcR+mZEwbQXvXC755cEW2rU50BKhZRMB4Jmh/Cyh66umY biLsm5KLTEp8DuBmUMiugX5ytXoffq3nAqC0V4sI= Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kWdZc-0042bs-6J; Sun, 25 Oct 2020 10:48:28 +0000 Date: Sun, 25 Oct 2020 10:48:27 +0000 Message-ID: <87y2juoa2s.wl-maz@kernel.org> From: Marc Zyngier To: Gavin Shan Cc: kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, will@kernel.org, alexandru.elisei@arm.com Subject: Re: [PATCH 3/3] KVM: arm64: Failback on unsupported huge page sizes In-Reply-To: <20201025002739.5804-4-gshan@redhat.com> References: <20201025002739.5804-1-gshan@redhat.com> <20201025002739.5804-4-gshan@redhat.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 EasyPG/1.0.0 Emacs/26.3 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: gshan@redhat.com, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, will@kernel.org, alexandru.elisei@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 25 Oct 2020 01:27:39 +0100, Gavin Shan wrote: > > The huge page could be mapped through multiple contiguous PMDs or PTEs. > The corresponding huge page sizes aren't supported by the page table > walker currently. > > This fails the unsupported huge page sizes to the near one. Otherwise, > the guest can't boot successfully: CONT_PMD_SHIFT and CONT_PTE_SHIFT > fail back to PMD_SHIFT and PAGE_SHIFT separately. > > Signed-off-by: Gavin Shan > --- > arch/arm64/kvm/mmu.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 0f51585adc04..81cbdc368246 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -793,12 +793,20 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > vma_shift = PMD_SHIFT; > #endif > > + if (vma_shift == CONT_PMD_SHIFT) > + vma_shift = PMD_SHIFT; > + > if (vma_shift == PMD_SHIFT && > !fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) { > force_pte = true; > vma_shift = PAGE_SHIFT; > } > > + if (vma_shift == CONT_PTE_SHIFT) { > + force_pte = true; > + vma_shift = PAGE_SHIFT; > + } > + > vma_pagesize = 1UL << vma_shift; > if (vma_pagesize == PMD_SIZE || vma_pagesize == PUD_SIZE) > fault_ipa &= ~(vma_pagesize - 1); Yup, nice catch. However, I think we should take this opportunity to rationalise the logic here, and catch future discrepancies (should someone add contiguous PUD or something similarly silly). How about something like this (untested): diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index cc323d96c9d4..d9a13a8a82e0 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -787,14 +787,31 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, vma_shift = PAGE_SHIFT; } - if (vma_shift == PUD_SHIFT && - !fault_supports_stage2_huge_mapping(memslot, hva, PUD_SIZE)) - vma_shift = PMD_SHIFT; + switch (vma_shift) { + case PUD_SHIFT: + if (fault_supports_stage2_huge_mapping(memslot, hva, PUD_SIZE)) + break; + fallthrough; - if (vma_shift == PMD_SHIFT && - !fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) { - force_pte = true; + case CONT_PMD_SHIFT: + vma_shift = PMD_SHIFT; + fallthrough; + + case PMD_SHIFT: + if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) + break; + fallthrough; + + case CONT_PTE_SHIFT: vma_shift = PAGE_SHIFT; + force_pte = true; + fallthrough; + + case PAGE_SHIFT: + break; + + default: + WARN_ONCE(1, "Unknown vma_shift %d", vma_shift); } vma_pagesize = 1UL << vma_shift; Thanks, M. -- Without deviation from the norm, progress is not possible. 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=-9.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS 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 0A59BC388F7 for ; Sun, 25 Oct 2020 10:48:36 +0000 (UTC) Received: from mm01.cs.columbia.edu (mm01.cs.columbia.edu [128.59.11.253]) by mail.kernel.org (Postfix) with ESMTP id 574D7223AC for ; Sun, 25 Oct 2020 10:48:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="Pxv8mT38" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 574D7223AC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvmarm-bounces@lists.cs.columbia.edu Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id A80FF4BA59; Sun, 25 Oct 2020 06:48:34 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Authentication-Results: mm01.cs.columbia.edu (amavisd-new); dkim=softfail (fail, message has been altered) header.i=@kernel.org Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id tXNp0mRy8hjb; Sun, 25 Oct 2020 06:48:33 -0400 (EDT) Received: from mm01.cs.columbia.edu (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 602FE4BA29; Sun, 25 Oct 2020 06:48:33 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mm01.cs.columbia.edu (Postfix) with ESMTP id 732C24B902 for ; Sun, 25 Oct 2020 06:48:32 -0400 (EDT) X-Virus-Scanned: at lists.cs.columbia.edu Received: from mm01.cs.columbia.edu ([127.0.0.1]) by localhost (mm01.cs.columbia.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id NL7e08rTUlOu for ; Sun, 25 Oct 2020 06:48:31 -0400 (EDT) Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by mm01.cs.columbia.edu (Postfix) with ESMTPS id 47D6E4B8F2 for ; Sun, 25 Oct 2020 06:48:31 -0400 (EDT) Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 1D03D222D9; Sun, 25 Oct 2020 10:48:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603622910; bh=zEZv+ZNBF+WLM11Idj/nftgE/O9ylhR81K3Yn2chkKs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Pxv8mT386ya9ViOoESPjvo/evUhJWVNTWQbTb6x3v1OTjDWsDVY/zuzO1vzSteNp8 /ftdUuJmDbhLucMIcPJddvcR+mZEwbQXvXC755cEW2rU50BKhZRMB4Jmh/Cyh66umY biLsm5KLTEp8DuBmUMiugX5ytXoffq3nAqC0V4sI= Received: from 78.163-31-62.static.virginmediabusiness.co.uk ([62.31.163.78] helo=wait-a-minute.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kWdZc-0042bs-6J; Sun, 25 Oct 2020 10:48:28 +0000 Date: Sun, 25 Oct 2020 10:48:27 +0000 Message-ID: <87y2juoa2s.wl-maz@kernel.org> From: Marc Zyngier To: Gavin Shan Subject: Re: [PATCH 3/3] KVM: arm64: Failback on unsupported huge page sizes In-Reply-To: <20201025002739.5804-4-gshan@redhat.com> References: <20201025002739.5804-1-gshan@redhat.com> <20201025002739.5804-4-gshan@redhat.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL/10.8 EasyPG/1.0.0 Emacs/26.3 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 62.31.163.78 X-SA-Exim-Rcpt-To: gshan@redhat.com, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, will@kernel.org, alexandru.elisei@arm.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Cc: will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Sun, 25 Oct 2020 01:27:39 +0100, Gavin Shan wrote: > > The huge page could be mapped through multiple contiguous PMDs or PTEs. > The corresponding huge page sizes aren't supported by the page table > walker currently. > > This fails the unsupported huge page sizes to the near one. Otherwise, > the guest can't boot successfully: CONT_PMD_SHIFT and CONT_PTE_SHIFT > fail back to PMD_SHIFT and PAGE_SHIFT separately. > > Signed-off-by: Gavin Shan > --- > arch/arm64/kvm/mmu.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c > index 0f51585adc04..81cbdc368246 100644 > --- a/arch/arm64/kvm/mmu.c > +++ b/arch/arm64/kvm/mmu.c > @@ -793,12 +793,20 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > vma_shift = PMD_SHIFT; > #endif > > + if (vma_shift == CONT_PMD_SHIFT) > + vma_shift = PMD_SHIFT; > + > if (vma_shift == PMD_SHIFT && > !fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) { > force_pte = true; > vma_shift = PAGE_SHIFT; > } > > + if (vma_shift == CONT_PTE_SHIFT) { > + force_pte = true; > + vma_shift = PAGE_SHIFT; > + } > + > vma_pagesize = 1UL << vma_shift; > if (vma_pagesize == PMD_SIZE || vma_pagesize == PUD_SIZE) > fault_ipa &= ~(vma_pagesize - 1); Yup, nice catch. However, I think we should take this opportunity to rationalise the logic here, and catch future discrepancies (should someone add contiguous PUD or something similarly silly). How about something like this (untested): diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index cc323d96c9d4..d9a13a8a82e0 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -787,14 +787,31 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, vma_shift = PAGE_SHIFT; } - if (vma_shift == PUD_SHIFT && - !fault_supports_stage2_huge_mapping(memslot, hva, PUD_SIZE)) - vma_shift = PMD_SHIFT; + switch (vma_shift) { + case PUD_SHIFT: + if (fault_supports_stage2_huge_mapping(memslot, hva, PUD_SIZE)) + break; + fallthrough; - if (vma_shift == PMD_SHIFT && - !fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) { - force_pte = true; + case CONT_PMD_SHIFT: + vma_shift = PMD_SHIFT; + fallthrough; + + case PMD_SHIFT: + if (fault_supports_stage2_huge_mapping(memslot, hva, PMD_SIZE)) + break; + fallthrough; + + case CONT_PTE_SHIFT: vma_shift = PAGE_SHIFT; + force_pte = true; + fallthrough; + + case PAGE_SHIFT: + break; + + default: + WARN_ONCE(1, "Unknown vma_shift %d", vma_shift); } vma_pagesize = 1UL << vma_shift; Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm