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 E9FDDC4332F for ; Mon, 7 Nov 2022 13:31:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229638AbiKGNbK (ORCPT ); Mon, 7 Nov 2022 08:31:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33540 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231324AbiKGNbF (ORCPT ); Mon, 7 Nov 2022 08:31:05 -0500 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0DBFA1B9FA for ; Mon, 7 Nov 2022 05:31:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1667827865; x=1699363865; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=v1gI9Pe6bvHrL0dWTyJyctWSrUg2IYLGOLoOANLiJ3Y=; b=FUE/MnYuJUdy5AfXF9/nr+Q9403SmU1wcQrDXeze85TLtywAhcV8zxje ko5A3ucGKlZrnUPSK6PnAmj2sMeZXCvmbl8jzX4ZVCRxh63OCCZy22irs pqMCG8FMNo+WtE1jZ/sPkgrQsysC3KBaaPZNEq82MWTOGSgpbHmNKsVwg MRHpfQFjcMoTgZ8t98t0UY/htBKoZfoHUVwyLwLfDKmg0UypNx+wiFXdg zNHgpVNlKWH8ZKBk7R/LbC+DdYkkLM1RodJIVgvYBNOwNGK9nMzlmNUi2 AuPCnBCbYacYmQwIIO/P1sN5IDkrcvVM0NUPt3dfvdPbS6cvlqGgbnWE4 g==; X-IronPort-AV: E=McAfee;i="6500,9779,10523"; a="297900053" X-IronPort-AV: E=Sophos;i="5.96,145,1665471600"; d="scan'208";a="297900053" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Nov 2022 05:31:04 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10523"; a="586968694" X-IronPort-AV: E=Sophos;i="5.96,145,1665471600"; d="scan'208";a="586968694" Received: from dkthrons-mobl2.amr.corp.intel.com (HELO [10.209.29.113]) ([10.209.29.113]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 Nov 2022 05:31:04 -0800 Message-ID: <3cdb5bf8-7f26-0416-46d2-a5640dd27f22@intel.com> Date: Mon, 7 Nov 2022 05:31:03 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Subject: Re: [PATCH 2/2] x86/tdx: Do not allow #VE due to EPT violation on the private memory Content-Language: en-US To: Guorui Yu , kirill.shutemov@linux.intel.com Cc: ak@linux.intel.com, bp@alien8.de, dan.j.williams@intel.com, david@redhat.com, elena.reshetova@intel.com, hpa@zytor.com, linux-kernel@vger.kernel.org, luto@kernel.org, mingo@redhat.com, peterz@infradead.org, sathyanarayanan.kuppuswamy@linux.intel.com, seanjc@google.com, tglx@linutronix.de, thomas.lendacky@amd.com, x86@kernel.org References: <20221028141220.29217-3-kirill.shutemov@linux.intel.com> <4bfcd256-b926-9b1c-601c-efcff0d16605@intel.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/6/22 21:10, Guorui Yu wrote: >> Without ATTR_SEPT_VE_DISABLE, a #VE can occur on basically any >> instruction.  We call those kinds of exceptions "paranoid entry" points. >>   They need special handling like the NMI or #MC handlers. >> >> I'd be happy to look at a patch that does the MMIO path check *and* >> turns the #VE handler into a robust entry point. >> >> Bonus points if you can do ~5 lines of C like the approach in this >> thread. > > Yes, there is a fix to satify your requirement and get the bouns points 😄 > > Please refer to > https://github.com/intel/tdx/commit/f045b0d52a5f7d8bf66cd4410307d05a90523f10 > > case EXIT_REASON_EPT_VIOLATION: > + if (!(ve->gpa & tdx_shared_mask())) { > + panic("#VE due to access to unaccepted memory. " > + "GPA: %#llx\n", ve->gpa); > + } > + > /* original from Kirill and Kuppuswamy */ > > It's already there, but it just didn't get into the main branch. Could you explain how that prevents the #VE from occurring in the "syscall gap" or in a place where the kernel is running with the user GSBASE value? It doesn't as far as I can tell. You need the SEPT_VE_DISABLE check for that.