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([2a01:cb1c:b26:7100:7654:8924:d030:917]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-36791d7a93bsm1332756f8f.81.2024.07.03.01.28.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Jul 2024 01:28:07 -0700 (PDT) Message-ID: <263476c5-1136-4128-9d9c-76d107a78cf7@gmail.com> Date: Wed, 3 Jul 2024 10:28:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH ats_vtd v5 04/22] intel_iommu: do not consider wait_desc as an invalid descriptor To: Yi Liu , 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> <6f94f4da-27fb-4f8e-adba-33a2f4c20fe5@intel.com> Content-Language: en-US From: cmd In-Reply-To: <6f94f4da-27fb-4f8e-adba-33a2f4c20fe5@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::131; envelope-from=clement.mathieudrif.etu@gmail.com; helo=mail-lf1-x131.google.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, 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 03/07/2024 09:29, Yi Liu wrote: > 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" Fine, will do > > 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 >