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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, 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 BFC30C4743C for ; Wed, 23 Jun 2021 12:23:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A56F36102A for ; Wed, 23 Jun 2021 12:23:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230512AbhFWM0F (ORCPT ); Wed, 23 Jun 2021 08:26:05 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:36412 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230438AbhFWMZ6 (ORCPT ); Wed, 23 Jun 2021 08:25:58 -0400 Message-Id: <20210623121451.712803952@linutronix.de> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1624451020; 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: content-transfer-encoding:content-transfer-encoding: references:references; bh=vrpMyLAY/eHEL3V09LBJSXc3hXm7xzNWgtjWNbJVyTU=; b=KT4/FUdP9N8dOKW7rcaBB0pvfnWcIsWFvu7x/nXdkLoNMDk1uo0ZhPkjGOiwc+rf3ixkiZ CB1hJWtXCrwrfUJZ/4d5BwYpuf09uccQF6TlDDtUI8wZNgW6hHvGQrCPmR6q8+xI8+5Bl9 uVNMuHGA2U0wAefVSZzkzlsfRWALLtB6OLnBuImElBOuW6mFq3RGkF6XGR6VSZNhdrOBaj ZPraiz6f0YCCOxXvrjj7jbC/9ubdpCi4cLE//623mYCXsG4f8Ec8zKWEC6IklujJ0TqSxS t61Ln5jIW1Fv+PRlOD19xXf0zYUAqlRKdtgnUObdbMkXOqlXeW1y4t7Hhn8MvQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1624451020; 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: content-transfer-encoding:content-transfer-encoding: references:references; bh=vrpMyLAY/eHEL3V09LBJSXc3hXm7xzNWgtjWNbJVyTU=; b=cK02rSadQcezpl/9DywbBWfJJWhMsAExaBBt35t3b6kD5ri4rnqFiwaE1OSE36LXl1+lzw 0ssu8IerLUoc99Bw== Date: Wed, 23 Jun 2021 14:01:31 +0200 From: Thomas Gleixner To: LKML Cc: Andy Lutomirski , Dave Hansen , Fenghua Yu , Tony Luck , Yu-cheng Yu , Sebastian Andrzej Siewior , Borislav Petkov , Peter Zijlstra , Kan Liang , "Chang Seok Bae" , Megha Dey , Oliver Sang Subject: [patch V4 04/65] x86/fpu: Make xfeatures_mask_all __ro_after_init References: <20210623120127.327154589@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-transfer-encoding: 8-bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Nothing has to modify this after init. But of course there is code which unconditionallqy masks xfeatures_mask_all on CPU hotplug. This goes unnoticed during boot hotplug because at that point the variable is still RW mapped. This is broken in several ways: 1) Masking this in post init CPU hotplug means that any modification of this state goes unnoticed until actual hotplug happens. 2) If that ever happens then these bogus feature bits are already populated all over the place and the system is in inconsistent state vs. the compacted XSTATE offsets. If at all then this has to panic the machine because the inconsistency cannot be undone anymore. Make this a one time paranoia check in xstate init code and disable xsave when this happens. Reported-by: Kan Liang Signed-off-by: Thomas Gleixner Reviewed-by: Borislav Petkov --- V3: New patch. Addresses the hotplug crash reported by Kan --- arch/x86/kernel/fpu/xstate.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-) --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -59,7 +59,7 @@ static short xsave_cpuid_features[] __in * This represents the full set of bits that should ever be set in a kernel * XSAVE buffer, both supervisor and user xstates. */ -u64 xfeatures_mask_all __read_mostly; +u64 xfeatures_mask_all __ro_after_init; static unsigned int xstate_offsets[XFEATURE_MAX] __ro_after_init = { [ 0 ... XFEATURE_MAX - 1] = -1}; @@ -213,19 +213,8 @@ void fpstate_sanitize_xstate(struct fpu */ void fpu__init_cpu_xstate(void) { - u64 unsup_bits; - if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask_all) return; - /* - * Unsupported supervisor xstates should not be found in - * the xfeatures mask. - */ - unsup_bits = xfeatures_mask_all & XFEATURE_MASK_SUPERVISOR_UNSUPPORTED; - WARN_ONCE(unsup_bits, "x86/fpu: Found unsupported supervisor xstates: 0x%llx\n", - unsup_bits); - - xfeatures_mask_all &= ~XFEATURE_MASK_SUPERVISOR_UNSUPPORTED; cr4_set_bits(X86_CR4_OSXSAVE); @@ -825,6 +814,7 @@ void __init fpu__init_system_xstate(void { unsigned int eax, ebx, ecx, edx; static int on_boot_cpu __initdata = 1; + u64 xfeatures; int err; int i; @@ -879,6 +869,8 @@ void __init fpu__init_system_xstate(void } xfeatures_mask_all &= fpu__get_supported_xfeatures_mask(); + /* Store it for paranoia check at the end */ + xfeatures = xfeatures_mask_all; /* Enable xstate instructions to be able to continue with initialization: */ fpu__init_cpu_xstate(); @@ -896,8 +888,18 @@ void __init fpu__init_system_xstate(void setup_init_fpu_buf(); setup_xstate_comp_offsets(); setup_supervisor_only_offsets(); - print_xstate_offset_size(); + /* + * Paranoia check whether something in the setup modified the + * xfeatures mask. + */ + if (xfeatures != xfeatures_mask_all) { + pr_err("x86/fpu: xfeatures modified from 0x%016llx to 0x%016llx during init, disabling XSAVE\n", + xfeatures, xfeatures_mask_all); + goto out_disable; + } + + print_xstate_offset_size(); pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n", xfeatures_mask_all, fpu_kernel_xstate_size,