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 EA194C0502C for ; Mon, 29 Aug 2022 12:28:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231374AbiH2M2K (ORCPT ); Mon, 29 Aug 2022 08:28:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44514 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229871AbiH2M1w (ORCPT ); Mon, 29 Aug 2022 08:27:52 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83C02AE205; Mon, 29 Aug 2022 05:11:24 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id B2F8A6123D; Mon, 29 Aug 2022 11:17:07 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C2E6FC433D7; Mon, 29 Aug 2022 11:17:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1661771827; bh=gcZSMS/DK5coU0N9vP5BKXdPmMcCP9sZHKX5Iz1YpP4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ujXWigU00y44mI2pEXTx2I0J+gH1regmgD+lP/imqFtAWjnCQER7n3n/uUUsj4zF0 9XymOfqBCL3DZyNmiBa2szuUXpWjr42vHqkdof2R8kqh8lA3CBS8je5FEYVAYJ6lO2 HKSDCKNnpfgd/XvzANJIvcav+oDkkGhscVXyGlwE= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jan Beulich , Borislav Petkov , Ingo Molnar , Juergen Gross , Lucas De Marchi Subject: [PATCH 5.19 109/158] x86/PAT: Have pat_enabled() properly reflect state when running on Xen Date: Mon, 29 Aug 2022 12:59:19 +0200 Message-Id: <20220829105813.685677959@linuxfoundation.org> X-Mailer: git-send-email 2.37.2 In-Reply-To: <20220829105808.828227973@linuxfoundation.org> References: <20220829105808.828227973@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Jan Beulich commit 72cbc8f04fe2fa93443c0fcccb7ad91dfea3d9ce upstream. After commit ID in the Fixes: tag, pat_enabled() returns false (because of PAT initialization being suppressed in the absence of MTRRs being announced to be available). This has become a problem: the i915 driver now fails to initialize when running PV on Xen (i915_gem_object_pin_map() is where I located the induced failure), and its error handling is flaky enough to (at least sometimes) result in a hung system. Yet even beyond that problem the keying of the use of WC mappings to pat_enabled() (see arch_can_pci_mmap_wc()) means that in particular graphics frame buffer accesses would have been quite a bit less optimal than possible. Arrange for the function to return true in such environments, without undermining the rest of PAT MSR management logic considering PAT to be disabled: specifically, no writes to the PAT MSR should occur. For the new boolean to live in .init.data, init_cache_modes() also needs moving to .init.text (where it could/should have lived already before). [ bp: This is the "small fix" variant for stable. It'll get replaced with a proper PAT and MTRR detection split upstream but that is too involved for a stable backport. - additional touchups to commit msg. Use cpu_feature_enabled(). ] Fixes: bdd8b6c98239 ("drm/i915: replace X86_FEATURE_PAT with pat_enabled()") Signed-off-by: Jan Beulich Signed-off-by: Borislav Petkov Acked-by: Ingo Molnar Cc: Cc: Juergen Gross Cc: Lucas De Marchi Link: https://lore.kernel.org/r/9385fa60-fa5d-f559-a137-6608408f88b0@suse.com Signed-off-by: Greg Kroah-Hartman --- arch/x86/mm/pat/memtype.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) --- a/arch/x86/mm/pat/memtype.c +++ b/arch/x86/mm/pat/memtype.c @@ -62,6 +62,7 @@ static bool __read_mostly pat_bp_initialized; static bool __read_mostly pat_disabled = !IS_ENABLED(CONFIG_X86_PAT); +static bool __initdata pat_force_disabled = !IS_ENABLED(CONFIG_X86_PAT); static bool __read_mostly pat_bp_enabled; static bool __read_mostly pat_cm_initialized; @@ -86,6 +87,7 @@ void pat_disable(const char *msg_reason) static int __init nopat(char *str) { pat_disable("PAT support disabled via boot option."); + pat_force_disabled = true; return 0; } early_param("nopat", nopat); @@ -272,7 +274,7 @@ static void pat_ap_init(u64 pat) wrmsrl(MSR_IA32_CR_PAT, pat); } -void init_cache_modes(void) +void __init init_cache_modes(void) { u64 pat = 0; @@ -313,6 +315,12 @@ void init_cache_modes(void) */ pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) | PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC); + } else if (!pat_force_disabled && cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) { + /* + * Clearly PAT is enabled underneath. Allow pat_enabled() to + * reflect this. + */ + pat_bp_enabled = true; } __init_cache_modes(pat);