From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E5CA4606A31F for ; Mon, 26 Oct 2026 18:06:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=lists.infradead.org header.i=@lists.infradead.org header.a=rsa-sha256 header.s=bombadil.20210309 header.b=DzGue2Nq; dkim=pass (1024-bit key, unprotected) header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=oiB7p4FK DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc: To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Unsubscribe-Post: List-Owner; bh=Dazdfuswvplzd+nZxkdJ2Trb6gBuPhP20O43N/pReRw=; b=DzGue2NqG+Ga4e wH3Ax/RWBRD+ZrFFzGCVeGoKRd8zqym9tZTWeNAtXIK+a3Dkqctusx+6bBjb2aWhW/+0741FPbzuF QYx8aJ4mOhZ2CddfO0SqxwxBCwd60bh7nBFtMy0vC2ZX+x6byteyf/oNs96GQXqSi2PIwRCfaMrP8 KZGeVSvMg7lKuTmFCTJqH1HwZzIWW9NJcJPgJFFngl8d6vuaYGa+hWt0DI/ecz+Ux5Y5r6GDTN8C1 h/zPZOZLniqZjjp/e53FNAo6k5wlyoOLdv9oA8qEd0vE2xTSA15SYBe7XOV6YZcn108Rv9TLK4EAH LKHaGTfFFQnX9WWufrbA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLP52-000000032Kv-2Oru; Mon, 26 Oct 2026 18:05:56 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xLP4z-000000032KX-25MT for linux-arm-kernel@lists.infradead.org; Mon, 26 Oct 2026 18:05:55 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 7783D19F6; Mon, 26 Oct 2026 11:05:47 -0700 (PDT) Received: from LeoBrasDK.cambridge.arm.com (LeoBrasDK.cambridge.arm.com [10.2.212.21]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id E9D403F7B4; Mon, 26 Oct 2026 11:05:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1793037950; bh=0Fm//jObvS8Sn73p6wEdeeyE1A5W+WdjYk5R853HCAU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oiB7p4FKmQfYPhak2KyREhmAxzj21VR9bO/7IkVcr4vAhuyPU4BxeGZVArbjZCBEd 7nzK9K8tzkV9r//ANLZIfuLWdMzOrAyY3poD5DzLJ8uSGtE5kCj10S9IqZQr1/eDt6 WhdNQVWRU4yJS35XoSMSRo4NhGpvYUfZQjEkElRo= From: Leonardo Bras To: Tian Zheng Cc: Leonardo Bras , maz@kernel.org, oupton@kernel.org, catalin.marinas@arm.com, will@kernel.org, corbet@lwn.net, pbonzini@redhat.com, yuzenghui@huawei.com, wangzhou1@hisilicon.com, yangjinqian1@huawei.com, caijian11@h-partners.com, liuyonglong@huawei.com, tangchengchang@huawei.com, yezhenyu2@huawei.com, yubihong@huawei.com, linuxarm@huawei.com, joey.gouly@arm.com, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, seiden@linux.ibm.com, suzuki.poulose@arm.com, fuad.tabba@linux.dev, mark.rutland@arm.com, seanjc@google.com, rdunlap@infradead.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, skhan@linuxfoundation.org Subject: Re: [PATCH v5 05/15] KVM: arm64: Harvest stage-2 dirty state into the host folio account Date: Mon, 26 Oct 2026 18:05:38 +0000 Message-ID: X-Mailer: git-send-email 2.56.0 In-Reply-To: <20260929103655.85107-6-zhengtian10@huawei.com> References: <20260929103655.85107-1-zhengtian10@huawei.com> <20260929103655.85107-6-zhengtian10@huawei.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: 8bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261026_110553_667703_37776622 X-CRM114-Status: GOOD ( 14.32 ) X-Spam-Score: -4.4 (----) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" X-Spam-Status: No, score=-9.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 Hi Tian, Sorry for the delay in reviewing... On Tue, Sep 29, 2026 at 06:36:45PM +0800, Tian Zheng wrote: > With VTCR_EL2.HD set, hardware promotes writable-clean descriptors to > writable-dirty without any VM exit, and the only record of the write > is the S2AP[1] bit in the stage-2 PTE. The write never passed through > the host stage-1, and no unmap path reads the bit, so the record dies > with the PTE and reclaim may discard written guest data (silent > corruption). Sorry, I didn't get what you are trying to achieve here. On your patch, I see you marking backing pages dirty at wrprotect and unmap walkers, and it's very confusing to me on why you are doing this. IIUC, what you are trying to do is make sure a page does not lose it's contents in case it is reclaimed by the OS. IIUC, when a page is reclaimed, it will unmap the S2 PTE, and save it's contents to swap, so when the guest read or write to that page will cause it to fault. The page can never be just unmaped, as if there was a single write to it, the backing pages should be writable, and the contents need to be saved somewhere. So, if I was able to understand your suggestion, we don't need to worry about this, and this patch wouldn't be necessary. Did you hit this issue? Can you please expand on your issue, if I could not describe it above? Thanks! Leo