From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B3EFE171C0 for ; Fri, 22 Sep 2023 16:00:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E2FCAC433C8; Fri, 22 Sep 2023 16:00:42 +0000 (UTC) Date: Fri, 22 Sep 2023 17:00:40 +0100 From: Catalin Marinas To: Shameer Kolothum Cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, maz@kernel.org, will@kernel.org, oliver.upton@linux.dev, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, zhukeqian1@huawei.com, jonathan.cameron@huawei.com, linuxarm@huawei.com Subject: Re: [RFC PATCH v2 6/8] KVM: arm64: Only write protect selected PTE Message-ID: References: <20230825093528.1637-1-shameerali.kolothum.thodi@huawei.com> <20230825093528.1637-7-shameerali.kolothum.thodi@huawei.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230825093528.1637-7-shameerali.kolothum.thodi@huawei.com> On Fri, Aug 25, 2023 at 10:35:26AM +0100, Shameer Kolothum wrote: > From: Keqian Zhu > > This function write protects all PTEs between the ffs and fls of mask. > There may be unset bits between this range. It works well under pure > software dirty log, as software dirty log is not working during this > process. > > But it will unexpectly clear dirty status of PTE when hardware dirty > log is enabled. So change it to only write protect selected PTE. Ah, I did wonder about losing the dirty status. The equivalent to S1 would be for kvm_pgtable_stage2_wrprotect() to set a software dirty bit. I'm only superficially familiar with how KVM does dirty tracking for live migration. Does it need to first write-protect the pages and disable DBM? Is DBM re-enabled later? Or does stage2_wp_range() with your patches leave the DBM on? If the latter, the 'wp' aspect is a bit confusing since DBM basically means writeable (and maybe clean). So better to have something like stage2_clean_range(). -- Catalin 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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 712E4E6FE58 for ; Fri, 22 Sep 2023 16:01:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=iHgcVrW1oHJEQR39i73k9vK3KleholpLuyBZyFhKAPI=; b=kNX2y4dXMAjs1X aOwg6aD5bg+BaXLEE8NWZZmbRJp/nf4Dbuo6IIvz2RksKg3eCKo/cJ3ry424rl8XMrFiwYfnVa/TH MVE7SCWQE0CfAwJHiuJ4ru1e9zAJGLQJFTj9N/pnLFtwylGavs8xx5Z0wknkXDA7dOzAMZ/34+DBS bKLiWvYIlzy9Hu1JCKtQONbNXZpKDpWxPsw5iedPXhsfPm/bJl4kEDsKKijXNddAh0h/F4Hc3QUSS qr+ZcsCEtgirHIWS9SdC6PtDuO22zrcy0EwCnTcRwEosmZ7rFA2zA62gGzSblfnimCJ+duoxWIVLL p7mvvbOGoC5mwy85Mfrw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qjiaH-009MUA-23; Fri, 22 Sep 2023 16:00:49 +0000 Received: from ams.source.kernel.org ([145.40.68.75]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qjiaE-009MTc-35 for linux-arm-kernel@lists.infradead.org; Fri, 22 Sep 2023 16:00:48 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by ams.source.kernel.org (Postfix) with ESMTP id 8D33DB823D1; Fri, 22 Sep 2023 16:00:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E2FCAC433C8; Fri, 22 Sep 2023 16:00:42 +0000 (UTC) Date: Fri, 22 Sep 2023 17:00:40 +0100 From: Catalin Marinas To: Shameer Kolothum Cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, maz@kernel.org, will@kernel.org, oliver.upton@linux.dev, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, zhukeqian1@huawei.com, jonathan.cameron@huawei.com, linuxarm@huawei.com Subject: Re: [RFC PATCH v2 6/8] KVM: arm64: Only write protect selected PTE Message-ID: References: <20230825093528.1637-1-shameerali.kolothum.thodi@huawei.com> <20230825093528.1637-7-shameerali.kolothum.thodi@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20230825093528.1637-7-shameerali.kolothum.thodi@huawei.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230922_090047_160162_16380E28 X-CRM114-Status: GOOD ( 13.51 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, Aug 25, 2023 at 10:35:26AM +0100, Shameer Kolothum wrote: > From: Keqian Zhu > > This function write protects all PTEs between the ffs and fls of mask. > There may be unset bits between this range. It works well under pure > software dirty log, as software dirty log is not working during this > process. > > But it will unexpectly clear dirty status of PTE when hardware dirty > log is enabled. So change it to only write protect selected PTE. Ah, I did wonder about losing the dirty status. The equivalent to S1 would be for kvm_pgtable_stage2_wrprotect() to set a software dirty bit. I'm only superficially familiar with how KVM does dirty tracking for live migration. Does it need to first write-protect the pages and disable DBM? Is DBM re-enabled later? Or does stage2_wp_range() with your patches leave the DBM on? If the latter, the 'wp' aspect is a bit confusing since DBM basically means writeable (and maybe clean). So better to have something like stage2_clean_range(). -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel