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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 A4EF5C32750 for ; Tue, 13 Aug 2019 10:01:55 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 7689D20663 for ; Tue, 13 Aug 2019 10:01:55 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="QToUqDwh" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7689D20663 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=d0Hrq+MHy7PwU8U1QsJuJ+g2FJYmWavrmiSaV95hf5s=; b=QToUqDwhzIsm7EbU9dL23ZCv6 kM/lW1c3t0FoTSsao6lKiOzmuYRf9ZXY8/HA1Adp9vqXS2gWO220cCNjYrYJMtou/l1rUFJhmGD1R Uocr6+wYgUws5+xzY567Tw6gN6J6SctTYC44YY8JgQJn49wlKoYoVYewZUlfiTuFN2XzrLGFiop2g Fg6zuTFbiZOn8H9kN7sOTGg1d87TnZYBTMnYFU1Tf2O1qT8MMaOmbzvPWqMEq2qM7zbCzaQe0h2HY pcJJlLZhYGZ7SsMQgLChumXnAFDCBd76Vo/FFf8oUlpMsi25RV7pzUUqhJW8AsNM2ms/AFvo0KI6n /J5207eWg==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hxTco-0006Ro-U1; Tue, 13 Aug 2019 10:01:54 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hxTcl-0006R3-Qc for linux-arm-kernel@lists.infradead.org; Tue, 13 Aug 2019 10:01:53 +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 231A6337; Tue, 13 Aug 2019 03:01:51 -0700 (PDT) Received: from dawn-kernel.cambridge.arm.com (unknown [10.1.197.116]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8AF8B3F706; Tue, 13 Aug 2019 03:01:50 -0700 (PDT) Subject: Re: [PATCH 2/2] arm64: Don't use KPTI where we have E0PD To: broonie@kernel.org, catalin.marinas@arm.com, will@kernel.org References: <20190812125738.17388-1-broonie@kernel.org> <20190812125738.17388-3-broonie@kernel.org> From: Suzuki K Poulose Message-ID: Date: Tue, 13 Aug 2019 11:01:49 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190812125738.17388-3-broonie@kernel.org> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190813_030151_904153_0A5FD180 X-CRM114-Status: GOOD ( 23.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 12/08/2019 13:57, Mark Brown wrote: > Since E0PD is intended to fulfil the same role as KPTI we don't need to > use KPTI on CPUs where E0PD is available, we can rely on E0PD instead. > Change the check that forces KPTI on when KASLR is enabled to check for > E0PD before doing so, CPUs with E0PD are not expected to be affected by > meltdown so should not need to enable KPTI for other reasons. > > Since we repeat the KPTI check for all CPUs we will still enable KPTI if > any of the CPUs in the system lacks E0PD. Since KPTI itself is not changed > by this patch once we enable KPTI we will do so for all CPUs. This is safe > but not optimally performant for such systems. > > KPTI can still be forced on from the command line if required. > > Signed-off-by: Mark Brown > --- > arch/arm64/kernel/cpufeature.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index 4aa1d2026bef..322004409211 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -995,7 +995,7 @@ static bool unmap_kernel_at_el0(const struct arm64_cpu_capabilities *entry, > > /* Useful for KASLR robustness */ > if (IS_ENABLED(CONFIG_RANDOMIZE_BASE) && kaslr_offset() > 0) { > - if (!__kpti_forced) { > + if (!__kpti_forced && !this_cpu_has_cap(ARM64_HAS_E0PD)) { > str = "KASLR"; > __kpti_forced = 1; > } Reviewed-by: Suzuki K Poulose _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel