From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-209.mta0.migadu.com (out-209.mta0.migadu.com [91.218.175.209]) (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 705CF4176D for ; Fri, 22 Sep 2023 16:59:16 +0000 (UTC) Date: Fri, 22 Sep 2023 16:59:08 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1695401954; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=y6/hQEMPVHQkW+VGeoG3f+C/qAx++wI6UHGjk2uuU5Q=; b=PKtkMDQtsJGBrPV3WbBf4dphx8J+NtrxPNNLjB6ssrYvNm6jqVgfH/aiga5EoTAXARCkWU 8N2mYGpI8ms+vfz5Sw349w/Fe85OH20Qy8UdurnX8iOd9YD7Czm3pBbpIYFFEaqHakIQzd jAEIhbt4CP2AZuvrHMlsXMwZcmggyOs= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Catalin Marinas Cc: Shameer Kolothum , kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, maz@kernel.org, will@kernel.org, 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: X-Migadu-Flow: FLOW_OUT On Fri, Sep 22, 2023 at 05:00:40PM +0100, Catalin Marinas wrote: > 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(). KVM has never enabled DBM and we solely rely on write-protection faults for dirty tracking. IOW, we do not have a writable-clean state for stage-2 PTEs (yet). -- Thanks, Oliver 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 81F80CD4846 for ; Fri, 22 Sep 2023 16:59:57 +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=ROsnF1cQOMzASZZhDKnY6T8xd7nCsigMIdIAvKMHg38=; b=WI8TIAyvfdolUl z3jvnUsk6K3ZpvAS3HwLFuF9A4nAXyDxKKLnZLCgqHCwYSd2kCoJkVTeXNNtEj4Gkn1wcHtvFrG4H gl5wQESnTyw+mqw1yohQhkwAFbXAVTrAx96Ve5Jeq/K3b9CYH06NVDgI2Ds9xPMfktZAYy9ux6Lhb Txpqnj+i44gDc4pXhGAFP4czzERIta36fC6xXmPTHhjd81j9Cbkn87yyhz4ToBln+L+FPmO3TNnEZ HK3um6TZT336ljq/EjL0HeVb+s6Utv8KJrxUUuoMSjZ25Z18aTxrqsRInbYB/nTW6xZZVkyasMy93 t8da3LN0ElPjJkkoFQYg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qjjV1-009SQo-2U; Fri, 22 Sep 2023 16:59:27 +0000 Received: from out-203.mta0.migadu.com ([2001:41d0:1004:224b::cb]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1qjjUx-009SPv-1B for linux-arm-kernel@lists.infradead.org; Fri, 22 Sep 2023 16:59:25 +0000 Date: Fri, 22 Sep 2023 16:59:08 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1695401954; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=y6/hQEMPVHQkW+VGeoG3f+C/qAx++wI6UHGjk2uuU5Q=; b=PKtkMDQtsJGBrPV3WbBf4dphx8J+NtrxPNNLjB6ssrYvNm6jqVgfH/aiga5EoTAXARCkWU 8N2mYGpI8ms+vfz5Sw349w/Fe85OH20Qy8UdurnX8iOd9YD7Czm3pBbpIYFFEaqHakIQzd jAEIhbt4CP2AZuvrHMlsXMwZcmggyOs= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Catalin Marinas Cc: Shameer Kolothum , kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, maz@kernel.org, will@kernel.org, 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: X-Migadu-Flow: FLOW_OUT X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230922_095923_863278_14C9C303 X-CRM114-Status: GOOD ( 16.82 ) 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, Sep 22, 2023 at 05:00:40PM +0100, Catalin Marinas wrote: > 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(). KVM has never enabled DBM and we solely rely on write-protection faults for dirty tracking. IOW, we do not have a writable-clean state for stage-2 PTEs (yet). -- Thanks, Oliver _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel