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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 62EF1C48BCF for ; Wed, 9 Jun 2021 12:46:45 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 2F1FF610E6 for ; Wed, 9 Jun 2021 12:46:45 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2F1FF610E6 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=8bytes.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.139324.257660 (Exim 4.92) (envelope-from ) id 1lqxbO-0003rO-DW; Wed, 09 Jun 2021 12:46:34 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 139324.257660; Wed, 09 Jun 2021 12:46:34 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lqxbO-0003rH-9j; Wed, 09 Jun 2021 12:46:34 +0000 Received: by outflank-mailman (input) for mailman id 139324; Wed, 09 Jun 2021 12:46:33 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lqxbN-0003rA-LL for xen-devel@lists.xenproject.org; Wed, 09 Jun 2021 12:46:33 +0000 Received: from theia.8bytes.org (unknown [2a01:238:4383:600:38bc:a715:4b6d:a889]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id a8e88f73-63c6-4ecb-8f9e-3e754a1751b2; Wed, 09 Jun 2021 12:46:32 +0000 (UTC) Received: by theia.8bytes.org (Postfix, from userid 1000) id C211341A; Wed, 9 Jun 2021 14:46:30 +0200 (CEST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: a8e88f73-63c6-4ecb-8f9e-3e754a1751b2 Date: Wed, 9 Jun 2021 14:46:29 +0200 From: Joerg Roedel To: Tianyu Lan Cc: kys@microsoft.com, haiyangz@microsoft.com, sthemmin@microsoft.com, wei.liu@kernel.org, decui@microsoft.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, x86@kernel.org, hpa@zytor.com, arnd@arndb.de, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, rppt@kernel.org, hannes@cmpxchg.org, cai@lca.pw, krish.sadhukhan@oracle.com, saravanand@fb.com, Tianyu.Lan@microsoft.com, konrad.wilk@oracle.com, hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com, boris.ostrovsky@oracle.com, jgross@suse.com, sstabellini@kernel.org, will@kernel.org, xen-devel@lists.xenproject.org, davem@davemloft.net, kuba@kernel.org, jejb@linux.ibm.com, martin.petersen@oracle.com, iommu@lists.linux-foundation.org, linux-arch@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, netdev@vger.kernel.org, vkuznets@redhat.com, thomas.lendacky@amd.com, brijesh.singh@amd.com, sunilmut@microsoft.com Subject: Re: [RFC PATCH V3 04/11] HV: Add Write/Read MSR registers via ghcb Message-ID: References: <20210530150628.2063957-1-ltykernel@gmail.com> <20210530150628.2063957-5-ltykernel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210530150628.2063957-5-ltykernel@gmail.com> On Sun, May 30, 2021 at 11:06:21AM -0400, Tianyu Lan wrote: > +void hv_ghcb_msr_write(u64 msr, u64 value) > +{ > + union hv_ghcb *hv_ghcb; > + void **ghcb_base; > + unsigned long flags; > + > + if (!ms_hyperv.ghcb_base) > + return; > + > + local_irq_save(flags); > + ghcb_base = (void **)this_cpu_ptr(ms_hyperv.ghcb_base); > + hv_ghcb = (union hv_ghcb *)*ghcb_base; > + if (!hv_ghcb) { > + local_irq_restore(flags); > + return; > + } > + > + memset(hv_ghcb, 0x00, HV_HYP_PAGE_SIZE); > + > + hv_ghcb->ghcb.protocol_version = 1; > + hv_ghcb->ghcb.ghcb_usage = 0; > + > + ghcb_set_sw_exit_code(&hv_ghcb->ghcb, SVM_EXIT_MSR); > + ghcb_set_rcx(&hv_ghcb->ghcb, msr); > + ghcb_set_rax(&hv_ghcb->ghcb, lower_32_bits(value)); > + ghcb_set_rdx(&hv_ghcb->ghcb, value >> 32); > + ghcb_set_sw_exit_info_1(&hv_ghcb->ghcb, 1); > + ghcb_set_sw_exit_info_2(&hv_ghcb->ghcb, 0); > + > + VMGEXIT(); This is not safe to use from NMI context. You need at least some checking or WARN_ON/assertion/whatever to catch cases where this is violated. Otherwise it will result in some hard to debug bug reports. Regards, Joerg