From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932899AbcLSJ4k (ORCPT ); Mon, 19 Dec 2016 04:56:40 -0500 Received: from terminus.zytor.com ([198.137.202.10]:56020 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932802AbcLSJ4e (ORCPT ); Mon, 19 Dec 2016 04:56:34 -0500 Date: Mon, 19 Dec 2016 01:56:20 -0800 From: tip-bot for Borislav Petkov Message-ID: Cc: jgross@suse.com, bp@suse.de, boris.ostrovsky@oracle.com, tglx@linutronix.de, hpa@zytor.com, linux-kernel@vger.kernel.org, mingo@kernel.org Reply-To: tglx@linutronix.de, boris.ostrovsky@oracle.com, bp@suse.de, jgross@suse.com, mingo@kernel.org, hpa@zytor.com, linux-kernel@vger.kernel.org In-Reply-To: <20161218164414.9649-4-bp@alien8.de> References: <20161218164414.9649-4-bp@alien8.de> To: linux-tip-commits@vger.kernel.org Subject: [tip:x86/urgent] x86/microcode/AMD: Do not load when running on a hypervisor Git-Commit-ID: a15a753539eca8ba243d576f02e7ca9c4b7d7042 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: a15a753539eca8ba243d576f02e7ca9c4b7d7042 Gitweb: http://git.kernel.org/tip/a15a753539eca8ba243d576f02e7ca9c4b7d7042 Author: Borislav Petkov AuthorDate: Sun, 18 Dec 2016 17:44:13 +0100 Committer: Thomas Gleixner CommitDate: Mon, 19 Dec 2016 10:46:20 +0100 x86/microcode/AMD: Do not load when running on a hypervisor Doing so is completely void of sense for multiple reasons so prevent it. Set dis_ucode_ldr to true and thus disable the microcode loader by default to address xen pv guests which execute the AP path but not the BSP path. By having it turned off by default, the APs won't run into the loader either. Also, check CPUID(1).ECX[31] which hypervisors set. Well almost, not the xen pv one. That one gets the aforementioned "fix". Also, improve the detection method by caching the final decision whether to continue loading in dis_ucode_ldr and do it once on the BSP. The APs then simply test that value. Signed-off-by: Borislav Petkov Tested-by: Juergen Gross Tested-by: Boris Ostrovsky Acked-by: Juergen Gross Link: http://lkml.kernel.org/r/20161218164414.9649-4-bp@alien8.de Signed-off-by: Thomas Gleixner --- arch/x86/kernel/cpu/microcode/core.c | 28 +++++++++++++++++++--------- 1 file changed, 19 insertions(+), 9 deletions(-) diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 6996413..c4bb2f7 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -44,7 +44,7 @@ #define DRIVER_VERSION "2.2" static struct microcode_ops *microcode_ops; -static bool dis_ucode_ldr; +static bool dis_ucode_ldr = true; LIST_HEAD(microcode_cache); @@ -76,6 +76,7 @@ struct cpu_info_ctx { static bool __init check_loader_disabled_bsp(void) { static const char *__dis_opt_str = "dis_ucode_ldr"; + u32 a, b, c, d; #ifdef CONFIG_X86_32 const char *cmdline = (const char *)__pa_nodebug(boot_command_line); @@ -88,8 +89,23 @@ static bool __init check_loader_disabled_bsp(void) bool *res = &dis_ucode_ldr; #endif - if (cmdline_find_option_bool(cmdline, option)) - *res = true; + if (!have_cpuid_p()) + return *res; + + a = 1; + c = 0; + native_cpuid(&a, &b, &c, &d); + + /* + * CPUID(1).ECX[31]: reserved for hypervisor use. This is still not + * completely accurate as xen pv guests don't see that CPUID bit set but + * that's good enough as they don't land on the BSP path anyway. + */ + if (c & BIT(31)) + return *res; + + if (cmdline_find_option_bool(cmdline, option) <= 0) + *res = false; return *res; } @@ -121,9 +137,6 @@ void __init load_ucode_bsp(void) if (check_loader_disabled_bsp()) return; - if (!have_cpuid_p()) - return; - vendor = x86_cpuid_vendor(); family = x86_cpuid_family(); @@ -157,9 +170,6 @@ void load_ucode_ap(void) if (check_loader_disabled_ap()) return; - if (!have_cpuid_p()) - return; - vendor = x86_cpuid_vendor(); family = x86_cpuid_family();