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 AAE4CC4321E for ; Mon, 30 May 2022 14:38:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242714AbiE3Ohp (ORCPT ); Mon, 30 May 2022 10:37:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40300 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239666AbiE3OSy (ORCPT ); Mon, 30 May 2022 10:18:54 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 78951123880; Mon, 30 May 2022 06:49:56 -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 2B4BC60FE3; Mon, 30 May 2022 13:49:47 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 805B4C385B8; Mon, 30 May 2022 13:49:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1653918586; bh=L4wMv7eVCEcb+Dh8ypbivhOGsg3GXEYdwwoPqDs6iew=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=YREmrXFtI44icoPO5FGfn7Q8FNRlNM88WzR+KkE7HDCwyKkfbzd6CGMpr9pcTme/k aojb0/elgumkP0e/h8LNJtcPxOpYXGft0JLQ5ZKwIh3AG7lpPoKM97btFiyVPEWEfe U0KGMeMSPZH3nadwdaBOW16nL7nd00mjtQAxVf9YL644cCV6eDFGHo2qE41SCewAif LD+7NLbzhFtS6JcHf0RyuwYDruuCloeH8lCCa5n5g3yeDg+ykqnrwSAajlXs30/B+C NBjNvlA70NEWC0oh1Oa/tVNENDyWPLEFrjmav/SaWXALaxVSK/5CoRbbs52TRvZ2WF 45ahy8fjClfWQ== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Kirill A. Shutemov" , Dave Hansen , Dan Williams , Thomas Gleixner , Sasha Levin , mingo@redhat.com, bp@alien8.de, x86@kernel.org Subject: [PATCH AUTOSEL 4.19 08/38] ACPICA: Avoid cache flush inside virtual machines Date: Mon, 30 May 2022 09:48:54 -0400 Message-Id: <20220530134924.1936816-8-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220530134924.1936816-1-sashal@kernel.org> References: <20220530134924.1936816-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Kirill A. Shutemov" [ Upstream commit e2efb6359e620521d1e13f69b2257de8ceaa9475 ] While running inside virtual machine, the kernel can bypass cache flushing. Changing sleep state in a virtual machine doesn't affect the host system sleep state and cannot lead to data loss. Before entering sleep states, the ACPI code flushes caches to prevent data loss using the WBINVD instruction. This mechanism is required on bare metal. But, any use WBINVD inside of a guest is worthless. Changing sleep state in a virtual machine doesn't affect the host system sleep state and cannot lead to data loss, so most hypervisors simply ignore it. Despite this, the ACPI code calls WBINVD unconditionally anyway. It's useless, but also normally harmless. In TDX guests, though, WBINVD stops being harmless; it triggers a virtualization exception (#VE). If the ACPI cache-flushing WBINVD were left in place, TDX guests would need handling to recover from the exception. Avoid using WBINVD whenever running under a hypervisor. This both removes the useless WBINVDs and saves TDX from implementing WBINVD handling. Signed-off-by: Kirill A. Shutemov Signed-off-by: Dave Hansen Reviewed-by: Dave Hansen Reviewed-by: Dan Williams Reviewed-by: Thomas Gleixner Link: https://lkml.kernel.org/r/20220405232939.73860-30-kirill.shutemov@linux.intel.com Signed-off-by: Sasha Levin --- arch/x86/include/asm/acenv.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/acenv.h b/arch/x86/include/asm/acenv.h index 1b010a859b8b..6de59a4f723c 100644 --- a/arch/x86/include/asm/acenv.h +++ b/arch/x86/include/asm/acenv.h @@ -16,7 +16,19 @@ /* Asm macros */ -#define ACPI_FLUSH_CPU_CACHE() wbinvd() +/* + * ACPI_FLUSH_CPU_CACHE() flushes caches on entering sleep states. + * It is required to prevent data loss. + * + * While running inside virtual machine, the kernel can bypass cache flushing. + * Changing sleep state in a virtual machine doesn't affect the host system + * sleep state and cannot lead to data loss. + */ +#define ACPI_FLUSH_CPU_CACHE() \ +do { \ + if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR)) \ + wbinvd(); \ +} while (0) int __acpi_acquire_global_lock(unsigned int *lock); int __acpi_release_global_lock(unsigned int *lock); -- 2.35.1