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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4238CECAAD5 for ; Fri, 2 Sep 2022 15:59:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237814AbiIBP7Y (ORCPT ); Fri, 2 Sep 2022 11:59:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58626 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237645AbiIBP7D (ORCPT ); Fri, 2 Sep 2022 11:59:03 -0400 Received: from out2.migadu.com (out2.migadu.com [IPv6:2001:41d0:2:aacc::]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF26AC6944 for ; Fri, 2 Sep 2022 08:52:53 -0700 (PDT) Date: Fri, 2 Sep 2022 15:52:48 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1662133972; 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=35qjFLrYT3buGXhS8Vj22dIHKr4JB5N0KAUbbHI8coY=; b=hk/3SguCOBwdLg4PaMV96tHvBax7zVDo2wR7UXE3ZRYJeJTiu1NlMCJWn19Bk9lzFxgdbn 28vyKfDFuCrsa0CBJfHtZiTOoOVGkVmKnxBOwGU1yiEPYsSH3WonrlhMx2g7Okx/kA9neo uuOob/7GeI76+AzjUE1RrGZjyOd3iqU= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Marc Zyngier , James Morse , Alexandru Elisei Cc: linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Reiji Watanabe Subject: Re: [PATCH v2 0/7] KVM: arm64: Use visibility hook to treat ID regs as RAZ Message-ID: References: <20220902154804.1939819-1-oliver.upton@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220902154804.1939819-1-oliver.upton@linux.dev> X-Migadu-Flow: FLOW_OUT X-Migadu-Auth-User: linux.dev Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org Lol, mess up my own copypasta: On Fri, Sep 02, 2022 at 03:47:56PM +0000, Oliver Upton wrote: > For reasons unknown, the Arm architecture defines the 64-bit views of > the 32-bit ID registers as UNKNOWN [1]. This combines poorly with the ^ on AArch64-only systems. > fact that KVM unconditionally exposes these registers to userspace, > which could throw a wrench in migration between 64-bit only systems. > > This series reworks KVM's definition of these registers to RAZ/WI with > the goal of providing consistent register values across 64-bit machines. > > Patches 1-3 clean up the ID register accessors, taking advantage of the > fact that the generic accessors know how to handle RAZ. > > Patches 4-6 start switch the handling of potentially nonzero AArch32 ID > registers to RAZ/WI. RAZ covers up the architecturally UNKNOWN values, > and WI allows for migration off of kernels that may provide garbage. > Note that hidden AArch32 ID registers continue to have RAZ behavior with > the additional expectation of invariance. > > Lastly, patch 7 includes a small test for the issue. > > Applies to 6.0-rc3. Tested with KVM selftests under the fast model w/ > asymmetric 32 bit support and no 32 bit support whatsoever. [1]: DDI0487H.a Table D12-2 'Instruction encodings for non-Debug System Register accesses' v1: https://lore.kernel.org/kvmarm/20220817214818.3243383-1-oliver.upton@linux.dev/ -- Thanks, Oliver > v1 -> v2: > - Collect Reiji's r-b tags (thanks!) > - Call sysreg_visible_as_raz() from read_id_reg() (Reiji) > - Hoist sysreg_user_write_ignore() into kvm_sys_reg_set_user() (Reiji) > > Oliver Upton (7): > KVM: arm64: Use visibility hook to treat ID regs as RAZ > KVM: arm64: Remove internal accessor helpers for id regs > KVM: arm64: Drop raz parameter from read_id_reg() > KVM: arm64: Spin off helper for calling visibility hook > KVM: arm64: Add a visibility bit to ignore user writes > KVM: arm64: Treat 32bit ID registers as RAZ/WI on 64bit-only system > KVM: selftests: Add test for RAZ/WI AArch32 ID registers > > arch/arm64/kvm/sys_regs.c | 150 +++++++++--------- > arch/arm64/kvm/sys_regs.h | 24 ++- > tools/testing/selftests/kvm/.gitignore | 1 + > tools/testing/selftests/kvm/Makefile | 1 + > .../kvm/aarch64/aarch64_only_id_regs.c | 135 ++++++++++++++++ > 5 files changed, 225 insertions(+), 86 deletions(-) > create mode 100644 tools/testing/selftests/kvm/aarch64/aarch64_only_id_regs.c > > > base-commit: b90cb1053190353cc30f0fef0ef1f378ccc063c5 > -- > 2.37.2.789.g6183377224-goog >