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 53753EE49A6 for ; Fri, 25 Aug 2023 07:02:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242780AbjHYHCU (ORCPT ); Fri, 25 Aug 2023 03:02:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58700 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S241488AbjHYHCH (ORCPT ); Fri, 25 Aug 2023 03:02:07 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0DF8AE6B for ; Fri, 25 Aug 2023 00:02:05 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (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 dfw.source.kernel.org (Postfix) with ESMTPS id A008863D4D for ; Fri, 25 Aug 2023 07:02:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A429BC433CB; Fri, 25 Aug 2023 07:02:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1692946924; bh=UvnB+1HRcJkP+iJJQOrqezgOZR8rm8LcTjqaiUaMuO8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hRtIRdIyzn9CR8R2LqOOBc6cqyI8Ggy0B8De8BVha9dFQdezBRBwBNoQYFVNe3y0Y gmsMFw/utGVnPE8Y6eB//Nc9qQpoeEOt3e3pN2R4YBclowPSyJ05TcT9PAzkVGEqLL y6D4Qnu3UhqOGBxC77w7owMpY24UV10GTgfIvILSQmF91NuKCGxuKzdcklVlK8l1l4 nFJL6Ta+IDhEyf5b1399j86TUsJA6BHaiBrMUUP+5Bl7rE4/k3kHCaGegHBh/yPFVa grN7upITlu156yYg+FNUJ/Qv3rMoRU6IfOox5nL3szeOS5uJoOGmbyMA0AfXMqUuFQ /tOncAJ0m44yw== From: Josh Poimboeuf To: x86@kernel.org Cc: linux-kernel@vger.kernel.org, Borislav Petkov , Peter Zijlstra , Babu Moger , Paolo Bonzini , Sean Christopherson , David.Kaplan@amd.com, Andrew Cooper , Nikolay Borisov , gregkh@linuxfoundation.org, Thomas Gleixner Subject: [PATCH 03/23] x86/srso: Don't probe microcode in a guest Date: Fri, 25 Aug 2023 00:01:34 -0700 Message-ID: <3e293282e96b9fe1835c8bd22d1aaac07d9628e7.1692919072.git.jpoimboe@kernel.org> X-Mailer: git-send-email 2.41.0 In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org To support live migration, the hypervisor sets the "lowest common denominator" of features. Probing the microcode isn't allowed because any detected features might go away after a migration. As Andy Cooper states: "Linux must not probe microcode when virtualised.  What it may see instantaneously on boot (owing to MSR_PRED_CMD being fully passed through) is not accurate for the lifetime of the VM." Rely on the hypervisor to set the needed IBPB_BRTYPE and SBPB bits. Fixes: 1b5277c0ea0b ("x86/srso: Add SRSO_NO support") Suggested-by: Andrew Cooper Signed-off-by: Josh Poimboeuf --- arch/x86/kernel/cpu/amd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index b08af929135d..28e77c5d6484 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -767,7 +767,7 @@ static void early_init_amd(struct cpuinfo_x86 *c) if (cpu_has(c, X86_FEATURE_TOPOEXT)) smp_num_siblings = ((cpuid_ebx(0x8000001e) >> 8) & 0xff) + 1; - if (!cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) { + if (!cpu_has(c, X86_FEATURE_HYPERVISOR) && !cpu_has(c, X86_FEATURE_IBPB_BRTYPE)) { if (c->x86 == 0x17 && boot_cpu_has(X86_FEATURE_AMD_IBPB)) setup_force_cpu_cap(X86_FEATURE_IBPB_BRTYPE); else if (c->x86 >= 0x19 && !wrmsrl_safe(MSR_IA32_PRED_CMD, PRED_CMD_SBPB)) { -- 2.41.0