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mx.microsoft.com 1; spf=pass smtp.mailfrom=intel.com; dmarc=pass action=none header.from=intel.com; dkim=pass header.d=intel.com; arc=none Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=intel.com; Received: from DS0PR11MB7529.namprd11.prod.outlook.com (2603:10b6:8:141::20) by DS0PR11MB6422.namprd11.prod.outlook.com (2603:10b6:8:c6::21) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.7719.29; Wed, 3 Jul 2024 07:25:33 +0000 Received: from DS0PR11MB7529.namprd11.prod.outlook.com ([fe80::d244:15cd:1060:941a]) by DS0PR11MB7529.namprd11.prod.outlook.com ([fe80::d244:15cd:1060:941a%3]) with mapi id 15.20.7719.022; Wed, 3 Jul 2024 07:25:33 +0000 Message-ID: <6f94f4da-27fb-4f8e-adba-33a2f4c20fe5@intel.com> Date: Wed, 3 Jul 2024 15:29:28 +0800 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH ats_vtd v5 04/22] intel_iommu: do not consider wait_desc as an invalid descriptor To: CLEMENT MATHIEU--DRIF , "qemu-devel@nongnu.org" CC: "jasowang@redhat.com" , "zhenzhong.duan@intel.com" , "kevin.tian@intel.com" , "joao.m.martins@oracle.com" , "peterx@redhat.com" , "mst@redhat.com" References: <20240702055221.1337035-1-clement.mathieu--drif@eviden.com> <20240702055221.1337035-5-clement.mathieu--drif@eviden.com> <655835f4-dd39-4360-9868-57abb8f9a3a3@intel.com> <26c57107-3b75-46d0-9191-32bc7572fb26@eviden.com> Content-Language: en-US From: Yi Liu In-Reply-To: <26c57107-3b75-46d0-9191-32bc7572fb26@eviden.com> Content-Type: text/plain; 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envelope-from=yi.l.liu@intel.com; helo=mgamail.intel.com X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 2024/7/2 23:29, CLEMENT MATHIEU--DRIF wrote: > > On 02/07/2024 15:33, Yi Liu wrote: >> Caution: External email. Do not open attachments or click links, >> unless this email comes from a known sender and you know the content >> is safe. >> >> >> On 2024/7/2 13:52, CLEMENT MATHIEU--DRIF wrote: >>> From: Clément Mathieu--Drif >>> >>> Signed-off-by: Clément Mathieu--Drif >>> Reviewed-by: Zhenzhong Duan >>> --- >>>   hw/i386/intel_iommu.c | 5 +++++ >>>   1 file changed, 5 insertions(+) >>> >>> diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c >>> index 98996ededc..71cebe2fd3 100644 >>> --- a/hw/i386/intel_iommu.c >>> +++ b/hw/i386/intel_iommu.c >>> @@ -3500,6 +3500,11 @@ static bool >>> vtd_process_wait_desc(IntelIOMMUState *s, VTDInvDesc *inv_desc) >>>       } else if (inv_desc->lo & VTD_INV_DESC_WAIT_IF) { >>>           /* Interrupt flag */ >>>           vtd_generate_completion_event(s); >>> +    } else if (inv_desc->lo & VTD_INV_DESC_WAIT_FN) { >>> +        /* >>> +         * SW = 0, IF = 0, FN = 1 >>> +         * Nothing to do as we process the events sequentially >>> +         */ >> >> This code looks a bit weird. SW field does not co-exist with IF. But >> either >> SW or IF can co-exist with FN flag. Is it? Have you already seen a wait >> descriptor that only has FN flag set but no SW nor IF flag? > Yes, my test suite triggers that condition I see. Spec indeed has such usage. Please add a comment for it. Since it does not need a response, so QEMU can just bypass it. Also please adjust the subject a bit. It's misleading. Perhaps "intel_iommu: Bypass barrier wait descriptor" Spec CH 7.10 a. Submit Invalidation Wait Descriptor (inv_wait_dsc) with Fence flag (FN=1) Set to Invalidation Queue. This ensures that all requests submitted to the Invalidation Queue ahead of this wait descriptor are processed and completed by remapping hardware before processing requests after the Invalidation Wait Descriptor. It is not required to specify SW flag (or IF flag) in this descriptor or for software to wait on its completion, as its function is to only act as a barrier. >> >>>       } else { >>>           error_report_once("%s: invalid wait desc: hi=%"PRIx64", >>> lo=%"PRIx64 >>>                             " (unknown type)", __func__, inv_desc->hi, >> >> -- >> Regards, >> Yi Liu -- Regards, Yi Liu