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=BAYES_00,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,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 14D53C433FE for ; Mon, 7 Dec 2020 15:56:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D8D8823731 for ; Mon, 7 Dec 2020 15:56:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727264AbgLGP4k (ORCPT ); Mon, 7 Dec 2020 10:56:40 -0500 Received: from mail.kernel.org ([198.145.29.99]:47182 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726046AbgLGP4j (ORCPT ); Mon, 7 Dec 2020 10:56:39 -0500 Received: from disco-boy.misterjones.org (disco-boy.misterjones.org [51.254.78.96]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 6113423741; Mon, 7 Dec 2020 15:55:58 +0000 (UTC) Received: from disco-boy.misterjones.org ([51.254.78.96] helo=www.loen.fr) by disco-boy.misterjones.org with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94) (envelope-from ) id 1kmIrk-00Gnm0-3l; Mon, 07 Dec 2020 15:55:56 +0000 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Date: Mon, 07 Dec 2020 15:55:56 +0000 From: Marc Zyngier To: Steven Price Cc: Catalin Marinas , Will Deacon , James Morse , Julien Thierry , Suzuki K Poulose , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave Martin , Mark Rutland , Thomas Gleixner , qemu-devel@nongnu.org, Juan Quintela , "Dr. David Alan Gilbert" , Richard Henderson , Peter Maydell , Haibo Xu , Andrew Jones Subject: Re: [PATCH v6 1/2] arm64: kvm: Save/restore MTE registers In-Reply-To: <03566358-21b0-11d9-c4f6-d07d137a1009@arm.com> References: <20201127152113.13099-1-steven.price@arm.com> <20201127152113.13099-2-steven.price@arm.com> <946b1e7b06c4d286a78cf61408e0fc8d@kernel.org> <03566358-21b0-11d9-c4f6-d07d137a1009@arm.com> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <07e40bbcf734e8c63630168406262bb2@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: steven.price@arm.com, catalin.marinas@arm.com, will@kernel.org, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave.Martin@arm.com, mark.rutland@arm.com, tglx@linutronix.de, qemu-devel@nongnu.org, quintela@redhat.com, dgilbert@redhat.com, richard.henderson@linaro.org, peter.maydell@linaro.org, Haibo.Xu@arm.com, drjones@redhat.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-12-07 14:48, Steven Price wrote: > On 03/12/2020 17:07, Marc Zyngier wrote: >> >>> diff --git a/arch/arm64/include/asm/sysreg.h >>> b/arch/arm64/include/asm/sysreg.h >>> index e2ef4c2edf06..b6668ffa04d9 100644 >>> --- a/arch/arm64/include/asm/sysreg.h >>> +++ b/arch/arm64/include/asm/sysreg.h >>> @@ -569,7 +569,8 @@ >>>  #define SCTLR_ELx_M    (BIT(0)) >>> >>>  #define SCTLR_ELx_FLAGS    (SCTLR_ELx_M  | SCTLR_ELx_A | SCTLR_ELx_C >>> | \ >>> -             SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB) >>> +             SCTLR_ELx_SA | SCTLR_ELx_I | SCTLR_ELx_IESB | \ >>> +             SCTLR_ELx_ITFSB) >>> >>>  /* SCTLR_EL2 specific flags. */ >>>  #define SCTLR_EL2_RES1    ((BIT(4))  | (BIT(5))  | (BIT(11)) | >>> (BIT(16)) | \ >>> diff --git a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h >>> b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h >>> index cce43bfe158f..45255ba60152 100644 >>> --- a/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h >>> +++ b/arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h >>> @@ -18,6 +18,11 @@ >>>  static inline void __sysreg_save_common_state(struct kvm_cpu_context >>> *ctxt) >>>  { >>>      ctxt_sys_reg(ctxt, MDSCR_EL1)    = read_sysreg(mdscr_el1); >>> +    if (system_supports_mte()) { >> >> Please move the per-VM predicate to this patch so that it can be used >> not to save/restore the MTE registers if we don't need to. > > There isn't a valid struct kvm_vcpu or struct kvm here. I know there's > ctx->__hyp_running_vcpu but AFAICT that is only valid with the host > context. We have per-CPU variables for the host context. If ctx->__hyp_running_vcpu is non NULL, you know you're on the host. > >> >>> +        ctxt_sys_reg(ctxt, RGSR_EL1)    = >>> read_sysreg_s(SYS_RGSR_EL1); >>> +        ctxt_sys_reg(ctxt, GCR_EL1)    = read_sysreg_s(SYS_GCR_EL1); >>> +        ctxt_sys_reg(ctxt, TFSRE0_EL1)    = >>> read_sysreg_s(SYS_TFSRE0_EL1); >>> +    } >> >> Overall, I still don't understand how this is going to work once >> we have MTE in the kernel. You mentioned having the ability to >> create turn off the tag checks at times, but I don't see that >> in this patch (and I'm not sure we want that either). > > Given that this is now highly unlikely to be merged for v5.11, I'll > rebase onto of the KASAN MTE series and double check exactly what > happens. My thought was that it should be as simple as setting TCO, > but your previous comment about moving the save/restore into assembler > might be wise in case the compiler starts playing with TCO itself. Indeed. Thanks, M. -- Jazz is not dead. It just smells funny...