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=-17.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 AE252C433ED for ; Thu, 1 Apr 2021 13:38:41 +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 58D9861244 for ; Thu, 1 Apr 2021 13:38:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 58D9861244 Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com 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.104458.199773 (Exim 4.92) (envelope-from ) id 1lRxWm-0005dm-Rm; Thu, 01 Apr 2021 13:38:28 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 104458.199773; Thu, 01 Apr 2021 13:38:28 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lRxWm-0005df-Of; Thu, 01 Apr 2021 13:38:28 +0000 Received: by outflank-mailman (input) for mailman id 104458; Thu, 01 Apr 2021 13:38:27 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1lRxWk-0005dV-T7 for xen-devel@lists.xenproject.org; Thu, 01 Apr 2021 13:38:26 +0000 Received: from mx2.suse.de (unknown [195.135.220.15]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id b03c95cd-c0d9-455d-8b49-73c7e0a9183d; Thu, 01 Apr 2021 13:38:25 +0000 (UTC) Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id EA57AB0E6; Thu, 1 Apr 2021 13:38:24 +0000 (UTC) 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: b03c95cd-c0d9-455d-8b49-73c7e0a9183d X-Virus-Scanned: by amavisd-new at test-mx.suse.de DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1617284305; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=YTyVyHfq5aXmFcqzWsVtaDBe2hBWqpTVqk6/vpdoImU=; b=Puh5c+7J9AL9Fr1Jhn9hilua2VmUG+8UqNSZZSAtb3OyOISHAWiO8mpSKfjibifkt2jNZ7 G3ok/41FItJOvRbZBXvhtVEEEJ7rj6D1Q6z4pl4npdybwI7avPUq7gtmTUWdASt6uzyxvz InZ66TA3bpDKnCMNy68uvtC1+ELaiIk= Subject: Re: [PATCH] x86/viridian: EOI MSR should always happen in affected vCPU context To: Andrew Cooper Cc: Paul Durrant , Wei Liu , xen-devel@lists.xenproject.org, Roger Pau Monne References: <20210401102252.95196-1-roger.pau@citrix.com> From: Jan Beulich Message-ID: <28f68328-9e5f-3f86-a56f-fcc9cf6ba303@suse.com> Date: Thu, 1 Apr 2021 15:38:24 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit On 01.04.2021 14:44, Andrew Cooper wrote: > On 01/04/2021 11:22, Roger Pau Monne wrote: >> The HV_X64_MSR_EOI wrmsr should always happen with the target vCPU >> as current, as there's no support for EOI'ing interrupts on a remote >> vCPU. >> >> While there also turn the unconditional assert at the top of the >> function into an error on non-debug builds. >> >> No functional change intended. >> >> Requested-by: Jan Beulich >> Signed-off-by: Roger Pau Monné >> --- >> xen/arch/x86/hvm/viridian/synic.c | 11 ++++++++++- >> 1 file changed, 10 insertions(+), 1 deletion(-) >> >> diff --git a/xen/arch/x86/hvm/viridian/synic.c b/xen/arch/x86/hvm/viridian/synic.c >> index 22e2df27e5d..e18538c60a6 100644 >> --- a/xen/arch/x86/hvm/viridian/synic.c >> +++ b/xen/arch/x86/hvm/viridian/synic.c >> @@ -79,11 +79,20 @@ int viridian_synic_wrmsr(struct vcpu *v, uint32_t idx, uint64_t val) >> struct viridian_vcpu *vv = v->arch.hvm.viridian; >> struct domain *d = v->domain; >> >> - ASSERT(v == current || !v->is_running); >> + if ( v != current && v->is_running ) >> + { >> + ASSERT_UNREACHABLE(); >> + return X86EMUL_EXCEPTION; >> + } > > The original ASSERT() was correct - both of these are easily reachable > in control domain context. > > If you want EOI to not be used, you need to raise #GP from it, but that > in principle breaks introspection which really does write MSRs on the > guests behalf. > > It's perhaps fine in principle to leave that problem to whomever first > wants to poke this MSR from introspection context, but the > ASSERT_UNREACHABLE()s need dropping whatever the introspection angle. But if the original ASSERT() was correct, how can the ASSERT_UNREACHABLE() above need dropping? Are you perhaps only talking about the other one? Jan