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 88213606A321 for ; Fri, 30 Oct 2026 11:51:22 +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=FK0/bnFL; dkim=pass (1024-bit key, unprotected) header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=lhbs403c 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=EV9q3xMYUg7eyUdptCPQkT+NInqEVi2Bft0i/3u9pWc=; b=FK0/bnFLnmr7vj tqNmcBQt+BafSK8zZ5e7MNYdK3H75zrTrcI5D0rIWe8om4jgqyhP2VfbvsFHHMVQbLCCGdQH83uaB DyM++JU9uOKdN8dIrFG43iO5QybGv6wB1kHKc1fAJNpbJkQ8pz8+Vr6Kth/M5DmarlkoiaHGK5e4c IGP1BT7sGPLDcC3XpIsdl+K3O8xshBI8ly9MhyAFm/ai15zpg4nUmj3vf1rTu80QvZE58Bc69m5kk zw07M29kUcb2bCUzC3EmQf2gYWN8/Jj9NA7JGqIjph2nGVB+2VSapofILr6FDtK3ri3Xrba0jfOuI yfzbIq3zq/dGGj2pbaoA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.100.1 #2 (Red Hat Linux)) id 1xMl8e-0000000BbJy-2RYe; Fri, 30 Oct 2026 11:51:16 +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 1xMl8d-0000000BbJa-05P7 for linux-arm-kernel@lists.infradead.org; Fri, 30 Oct 2026 11:51:16 +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 2A79E1682; Fri, 30 Oct 2026 04:51:10 -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 A3AE73F7B4; Fri, 30 Oct 2026 04:51:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1793361073; bh=Mc3ZxWgjpeC+0tTsnex0ZyBfJ8y4oR4Ncako7tOwxzw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=lhbs403ceP0i6J8ZnKQpDhpeznmarJmBUeflvdmtHnlB2nPAIKDzzcVGkjSj9dQ7W vtYBO7rtqa2fVQpvzW5QK31u40tMnW4Jc2IGyVrESGNTwnIebruQEJnQGn+OPTDhPw Gf2ge37yfRyKGQJ5KxdYYDrHf/8gyFWRm3p7HOp4= From: Leonardo Bras To: Tian Zheng Cc: Leonardo Bras , liuyonglong , Oliver Upton , Marc Zyngier , Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Mark Rutland , Raghavendra Rao Ananta , linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, Zhou Wang Subject: Re: [RFC PATCH 5/5] KVM: arm64: Enable HAFDBS for guests not on migration Date: Fri, 30 Oct 2026 11:51:08 +0000 Message-ID: X-Mailer: git-send-email 2.56.0 In-Reply-To: References: <3e464bef-8dfe-44a3-afea-3c276ae87cd8@huawei.com> <8eaaba87-7881-49c4-a76a-51dec2f29ffc@huawei.com> <52945586-8c5c-4991-bd92-fe02aaf79fbe@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-20261030_045115_120608_FF695896 X-CRM114-Status: GOOD ( 23.59 ) 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=-8.9 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 On Fri, Oct 30, 2026 at 02:01:49PM +0800, Tian Zheng wrote: > > > On 10/29/2026 7:54 PM, Leonardo Bras wrote: > > On Thu, Oct 29, 2026 at 10:54:24AM +0800, Tian Zheng wrote: > > > Hi Leo, > > > > > > I've read your discussion with Oliver on DBM RFC v2. As a suggestion, > > > maybe we should go with Oliver's approach, i.e. revert to the v1 scheme > > > and continue fixing from there. > > > > Hi Tian, > > I have been reading a bit more about permission indirection to try figuring > > out a way that the change may work for both ways. > > > > The problem with the previous approach is that it assume DBM=write at all > > times, which is not architecturally correct. Having DBM=write only on > > HAFDBS=on as suggested would require us to transverse the whole pagetable > > to convert encodings when we enable/disable it, which can be quite > > expensive. > > > > One option would be to always enable HAFDBS when system supports HDBSS, but > > I still have to figure out if that causes any performance regression before > > suggesting. > > > > The option I am pursuing is thinking on an unified code path for direct > > permissison (both HACDBS=on and HACDBS=off) so we don't have to convert > > between them, neither worry about the impact of HAFDBS=on on performance. > > > > I will reply on the thread once I figure one of those options out. > > > > Thanks! > > Leo > > Hi Leo, > > Sounds good. I'll wait for your next version and review it once it's > posted. > > Thanks, > Tian Awesome, thanks! Leo