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 198F2C6FA82 for ; Wed, 14 Sep 2022 15:46:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229933AbiINPqZ (ORCPT ); Wed, 14 Sep 2022 11:46:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40912 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229963AbiINPqY (ORCPT ); Wed, 14 Sep 2022 11:46:24 -0400 Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3E39D270C for ; Wed, 14 Sep 2022 08:46:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1663170383; x=1694706383; h=to:cc:subject:references:date:mime-version: content-transfer-encoding:from:message-id:in-reply-to; bh=5q7Lata1AlrnMorTzcoBuTqzSsws7pkMctr9+HLMcAw=; b=UO1rUcwX6ePnVDYbH8QYDDuEj1S91LAhA8lwGm107RXmWjNPkHxsJrXb yarTRW3AGk4GTpfK0jPLRPYtrsfKBipyUhwYjKOIbzPAv8WCh1wRgdeMU SEzqqYYyJISESyQes82QgrQFPaLCEc0aKQlrDOfMmkNGAauocf1npwAPZ qHFUibce0y0Z83u8vypj3uFamd3ZNSQsCyfGiAvARXFMDuTNePCgEhGKW Ko8yQgaRdGjQt86FekbUdJStn939n/BMiLMKSuhuFUMmAYgttFDtQPKPc zg3lWgMA8wHylhuU9WsVViadP9BIg2FaaWwJiIHZ1zmB+BVTj9ruE03ui w==; X-IronPort-AV: E=McAfee;i="6500,9779,10470"; a="285502436" X-IronPort-AV: E=Sophos;i="5.93,315,1654585200"; d="scan'208";a="285502436" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 14 Sep 2022 08:46:22 -0700 X-IronPort-AV: E=Sophos;i="5.93,315,1654585200"; d="scan'208";a="619353815" Received: from hhuan26-mobl1.amr.corp.intel.com (HELO hhuan26-mobl1.mshome.net) ([10.212.25.253]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-SHA; 14 Sep 2022 08:46:21 -0700 Content-Type: text/plain; charset=iso-8859-15; format=flowed; delsp=yes To: linux-sgx@vger.kernel.org, tony.luck@intel.com, jarkko@kernel.org, dave.hansen@linux.intel.com, tglx@linutronix.de, bp@alien8.de, "Zhiquan Li" Cc: seanjc@google.com, kai.huang@intel.com, fan.du@intel.com, cathy.zhang@intel.com Subject: Re: [PATCH v8 2/3] x86/sgx: Introduce union with vepc_vaddr field for virtualization case References: <20220913145330.2998212-1-zhiquan1.li@intel.com> <20220913145330.2998212-3-zhiquan1.li@intel.com> Date: Wed, 14 Sep 2022 10:46:17 -0500 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit From: "Haitao Huang" Organization: Intel Corp Message-ID: In-Reply-To: <20220913145330.2998212-3-zhiquan1.li@intel.com> User-Agent: Opera Mail/1.0 (Win32) Precedence: bulk List-ID: X-Mailing-List: linux-sgx@vger.kernel.org Hi Zhiquan On Tue, 13 Sep 2022 09:53:29 -0500, Zhiquan Li wrote: > When a page triggers a machine check, it only reports the PFN. But in > order to inject #MC into hypervisor, the virtual address is required. > The 'encl_owner' field is useless in virtualization case, then > repurpose it as 'vepc_vaddr' - the virtual address of the virtual EPC > page for such case so that arch_memory_failure() can easily retrieve it. > > Introduce a union to prevent adding a new dedicated structure to > track the virtual address of virtual EPC page. And it can also prevent > playing the casting games while using it. > > Add a new EPC page flag - SGX_EPC_PAGE_KVM_GUEST to interpret the > meaning of the field. > > Co-developed-by: Cathy Zhang > Signed-off-by: Cathy Zhang > Signed-off-by: Zhiquan Li > Acked-by: Kai Huang > Reviewed-by: Jarkko Sakkinen > Acked-by: Jarkko Sakkinen > > --- > Changes since V7: > - Add Acked-by from Jarkko. > > No changes since V6. > > Changes since V5: > - To prevent casting the 'encl_owner' field, introduce a union with > another field - 'vepc_vaddr', sugguested by Dave Hansen. > - Add Reviewed-by from Jarkko. > Link: > https://lore.kernel.org/linux-sgx/Yrf27fugD7lkyaek@kernel.org/T/#m379d00fc7f1d43726a42b3884637532061a8c0d1 > > Changes since V4: > - Add Co-developed-by and Signed-off-by from Cathy Zhang, as she had > fully discussed the flag name with Jarkko. > Link: > https://lore.kernel.org/all/df92395ade424401ac3c6322de568720@intel.com/ > - Add Acked-by from Kai Huang > Link: > https://lore.kernel.org/linux-sgx/0676cd4e-d94b-e904-81ae-ca1c05d37070@intel.com/T/#mccfb11df30698dbd060f2b6f06383cda7f154ef3 > > Changes since V3: > - Take the definition of EPC page flag SGX_EPC_PAGE_KVM_GUEST from > Cathy Zhang's third patch of SGX rebootless recovery patch set but > discard irrelevant portion, since it might need some time to > re-forge and these are two different features. > Link: > https://lore.kernel.org/linux-sgx/41704e5d4c03b49fcda12e695595211d950cfb08.camel@kernel.org/T/#m9782d23496cacecb7da07a67daa79f4b322ae170 > > Changes since V2: > - Remove struct sgx_vepc_page and relevant code. > - Rework the patch suggested by Jarkko. > - Remove new EPC page flag SGX_EPC_PAGE_IS_VEPC definition as it is > duplicated to SGX_EPC_PAGE_KVM_GUEST. > Link: > https://lore.kernel.org/linux-sgx/eb95b32ecf3d44a695610cf7f2816785@intel.com/T/#u > > Changes since V1: > - Add documentation suggested by Jarkko. > --- > arch/x86/kernel/cpu/sgx/main.c | 4 ++++ > arch/x86/kernel/cpu/sgx/sgx.h | 8 +++++++- > arch/x86/kernel/cpu/sgx/virt.c | 4 +++- > 3 files changed, 14 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/cpu/sgx/main.c > b/arch/x86/kernel/cpu/sgx/main.c > index 1315c69a733e..b319bedcaf1e 100644 > --- a/arch/x86/kernel/cpu/sgx/main.c > +++ b/arch/x86/kernel/cpu/sgx/main.c > @@ -549,6 +549,10 @@ int sgx_unmark_page_reclaimable(struct sgx_epc_page > *page) > * Finally, wake up ksgxd when the number of pages goes below the > watermark > * before returning back to the caller. > * > + * When an EPC page is assigned to KVM guest, repurpose the > 'encl_owner' field > + * as the virtual address of virtual EPC page, since it is useless in > such > + * scenario, so 'owner' is assigned to 'vepc_vaddr'. > + * > * Return: > * an EPC page, > * -errno on error > diff --git a/arch/x86/kernel/cpu/sgx/sgx.h > b/arch/x86/kernel/cpu/sgx/sgx.h > index 4d88abccd12e..d16a8baa28d4 100644 > --- a/arch/x86/kernel/cpu/sgx/sgx.h > +++ b/arch/x86/kernel/cpu/sgx/sgx.h > @@ -28,12 +28,18 @@ > /* Pages on free list */ > #define SGX_EPC_PAGE_IS_FREE BIT(1) > +/* Pages allocated for KVM guest */ > +#define SGX_EPC_PAGE_KVM_GUEST BIT(2) > struct sgx_epc_page { > unsigned int section; > u16 flags; > u16 poison; > - struct sgx_encl_page *encl_owner; > + union { > + struct sgx_encl_page *encl_owner; > + /* Use when SGX_EPC_PAGE_KVM_GUEST set in ->flags: */ > + void __user *vepc_vaddr; > + }; Maybe it's just me missing some prior knowledge. It's not obvious to me why you don't need any guard accessing the encl_owner field in ksgxd thread. Is it because all vepc pages are never put in the active list and encl_owner would never be null for all pages in that list? Regardless, could you add a few sentence here to to make the rule explicit? Thanks Haitao