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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,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 EA128C43381 for ; Fri, 22 Feb 2019 10:38:23 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id A1C5420652 for ; Fri, 22 Feb 2019 10:38:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A1C5420652 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 445SVP5mDHzDqVd for ; Fri, 22 Feb 2019 21:38:21 +1100 (AEDT) Received: from ozlabs.org (bilbo.ozlabs.org [203.11.71.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 445RNQ6Xb1zDq7k for ; Fri, 22 Feb 2019 20:48:06 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=ellerman.id.au Received: by ozlabs.org (Postfix) id 445RNQ37Mnz9sBp; Fri, 22 Feb 2019 20:48:06 +1100 (AEDT) Received: by ozlabs.org (Postfix, from userid 1034) id 445RNQ0njMz9sBR; Fri, 22 Feb 2019 20:48:05 +1100 (AEDT) X-powerpc-patch-notification: thanks X-powerpc-patch-commit: d976f6807ea613c54fcb74bd7ae68a43fdd62e1f X-Patchwork-Hint: ignore In-Reply-To: <20190220085500.29837-1-mpe@ellerman.id.au> To: Michael Ellerman , linuxppc-dev@ozlabs.org From: Michael Ellerman Subject: Re: KVM: PPC: Book3S HV: Context switch IAMR on Power9 Message-Id: <445RNQ0njMz9sBR@ozlabs.org> Date: Fri, 22 Feb 2019 20:48:05 +1100 (AEDT) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: paulus@samba.org, kvm-ppc@vger.kernel.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, 2019-02-20 at 08:55:00 UTC, Michael Ellerman wrote: > kvmhv_p9_guest_entry() implements a fast-path guest entry for Power9 > when guest and host are both running with the Radix MMU. > > Currently in that path we don't save the host AMR (Authority Mask > Register) value, and we always restore 0 on return to the host. That > is OK at the moment because the AMR is not used for storage keys with > the Radix MMU. > > However we plan to start using the AMR on Radix to prevent the kernel > from reading/writing to userspace outside of copy_to/from_user(). In > order to make that work we need to save/restore the AMR value. > > We only restore the value if it is different from the guest value, > which is already in the register when we exit to the host. This should > mean we rarely need to actually restore the value when running a > modern Linux as a guest, because it will be using the same value as > us. > > Signed-off-by: Michael Ellerman > Tested-by: Russell Currey Applied to powerpc next. https://git.kernel.org/powerpc/c/d976f6807ea613c54fcb74bd7ae68a43 cheers